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Withdrawn Document Railway Uncontrolled When Printed Group Approved Code of Practice

GK/RC0752 Issue Two Date December 1998

General Information on Track Circuits

Synopsis General information to ensure that the Integrity of Track Circuits is maintained at all times.

Approved by

Signatures removed from electronic version

Keith Turner Standards Project Manager Authorised by

This document is the property of Railtrack PLC. It shall not be reproduced in whole or in part without the written permission of the Controller, Railway Group Standards, Railtrack PLC. Published by Safety & Standards Directorate, Railtrack PLC, Floor DP01, Railtrack House, Euston Square, London NW1 2EE © Copyright 1998 Railtrack PLC

Richard Spoors Controller, Railway Group Standards

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General Information on Track Circuits

GK/RC0752 Issue Two Date December 1998 Page 1 of 2

Contents

Section Part A Issue Record Distribtuion Health and Safety Responsibilities Supply Part B 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Part C 1 2 3 4 Part D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 A1 A1 A1 A1 Description Page

Purpose Scope Glossary of Terms Limitations Introduction Electrical Behaviour of Railway track Operation and Adjustment of the Simple Track Circuit Train Shunt Imperfection Detection of "Lightweight" Vehicles Track Circuit Insulations Bonding Mutual Interference Between Track Circuits Detection of Rail Breaks Jointless Track Circuits Track Circuits and Electric Traction The Impedance Bonds Schematic Symbols Introduction Drawing Symbols on Bonding Plans Traction Return Bonding Symbols Civil Engineer's Scale Diagrams Planning and Design Introduction Responsibilities for Bonding Design Track Circuit Nomenclature Choice of Track Circuit Type Cut Sections Operating Times Track Circuit Interrupters Length of Track Circuits Track Circuit Gaps and Staggered IRJs Selective Operation of Track Circuits Bad Rail Surface Emergency Cross­overs Insulated Rail Joints and Bonding Track Circuit Equipment Positioning Layout and Wiring of Lineside Apparatus Housing Duplicate Rail Connections Communications

B1 B1 B1 B5 B6 B7 B9 B10 B12 B13 B16 B18 B19 B20 B21 B24

C1 C1 C8 C10

D1 D1 D2 D3 D5 D6 D8 D8 D9 D9 D9 D10 D10 D19 D19 D20 D21

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General Information on Track Circuits

Section Part E 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Part F 1 2 3 4 5 6

Description Components and Installation Introduction Responsibilities for Bonding Installation Track Circuit Interrupters Identification of Track Circuit Boundaries Protection of Cross Track Cables Mechanised track Maintenance Rail Drilling Rail Connections Track Circuit Disconnection Box Arrangement of Track Lead Rail Connections (Except Jointless) Fishplate Bonding Jumper Bonding High Voltages Lineside Apparatus Housing Wiring Impedance Bonds Impedance Bond Installation Aluminium Busbars Side Leads Traction Negative Return Jumpers Instrumentation Description and Use Introduction Multi­meters The Universal Shunt Box Rail Clip Insulation Tester Track Circuit Fault Detector Mark 4 Direct Reading Phase Angle Meter

Page

E1 E1 E2 E3 E3 E6 E6 E7 E17 E19 E21 E23 E24 E24 E25 E30 E37 E46 E52

F1 F1 F1 F2 F4 F5

Part G 1 2 3 4 5 6 Part H 1 2 3 4 Part J 1 2 3 4 5 References

Testing and Commissioning Introduction High Voltages Lineside Apparatus Housing Inspection Bonding Inspection IRJ Inspection Performance Test Maintenance Introduction Routine Examination Drop Shunt Test Full Test Fault Finding Introduction Categories of Failure Intermittent Failures Right Side Failures Wrong Side Failures

G1 G1 G1 G1 G2 G2

H1 H1 H1 H2

J1 J1 J1 J2 J4 Ref 1

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Part A

Issue Record

This Approved Code of Practice will be updated when necessary by distribution of a replacement Part A and such other parts as are amended. Amended or additional parts of revised pages will be marked by a vertical black line in the adjacent margin. Part Part A Part B Part C Part D Part E Part F Part G Part H Part I Part J References Part A Part B Part C Part D Part E Part F Part G Part H Part I Part J References Issue One One One One One One One One not used. One One Two Two Two Two Two Two Two Two not used. Two Two Date August 1994 August 1994 August 1994 August 1994 August 1994 August 1994 August 1994 August 1994 August 1994 August 1994 December 1998 December 1998 December 1998 December 1998 December 1998 December 1998 December 1998 December 1998 Comments Original document. Original document. Original document. Original document. Original document. Original document. Original document. Original document. Original document. Original document. Revised document. Revised document. Revised document. Revised document. Revised document. Revised document. Revised document. Revised document.

December 1998 Revised document. December 1998 Revised document.

Distribution

Controlled copies of this Approved Code of Practice should be made available to all personnel who are responsible for the design, installation, testing, maintenance and faulting of Track Circuits.

Health and Safety Responsibilities

In issuing this Approved Code of Practice, Railtrack PLC makes no warranties, express or implied, that compliance with all or any Railway Group Standards or Codes of Practice is sufficient on its own to ensure safe systems of work or operation. Each user is reminded of its own responsibilities to ensure health and safety at work and its individual duties under health and safety legislation.

Supply

Controlled and uncontrolled copies of this Approved Code of Practice may be obtained from the Industry Safety Liaison Dept, Safety and Standards Directorate, Railtrack PLC, Railtrack House DP01, Euston Square, London, NW1 2EE.

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Part B

1 Purpose

This Approved Code of Practice gives details of best practice in respect of track circuits in general, in order to achieve the requirements of GK/RT 0251.

2 Scope

The contents of this Approved Code of Practice apply to all track circuits.

3 Glossary of Terms

The definitions of terms used by Signal Engineers vary depending on the location in which they were trained. The following terms will be used as standard throughout this handbook. Bearer An item of steel or concrete of non­standard dimensions used to support the track in S & C areas (see Sleeper and Timber). Bonding The electrical connection from one rail or part of a track circuit to any other rail or part of the track circuit. Cross Bond A traction bond cross connecting the traction rails of parallel tracks to form a mesh of alternate paths for traction return current. Fishplate Bond Provided to ensure electrical continuity between two rails mechanically connected by a steel fishplate. Impedance Bond Special device which presents a low impedance to traction current and a higher impedance to track circuit current. Parallel Bonding If any section of a track circuit is bonded in parallel to other sections of that track circuit, a disconnection will not cause the track circuit to indicate the presence of a train. The actual presence of a train within that section may not be indicated under certain failure conditions. This method of bonding is defined as Parallel Bonding and is the non­preferred method of bonding. Where it cannot be avoided, special precautions must be taken (see individual Sections). Red Bond A traction bond that has been designated by the Electrification Engineer as being dangerous to staff if disconnected. It is coloured red for identification. The Electric Control Room shall be advised whenever a disconnected red bond is observed. Series Bonding Series bonding is where the track is bonded together in series, so that if any short circuit or disconnection occurs, the track circuit will indicate the apparent presence of a train. It is the preferred method of bonding. Structure Bond A bond that connects adjacent lineside metal structures to the traction return rail system to ensure staff safety through equi­potential zoning. Traction Bond A cable specifically provided for continuity of traction current return, although it may additionally carry track circuit current. RAILTRACK B1

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General Information on Track Circuits

Traction Return Bonding The bonding required to carry the traction return current on both a.c. and d.c. electrified lines. Traction return bonding is generally parallel bonded. Transposition Bond A jumper cable where track circuit polarities and/or traction return rails are switched across a pair of IRJs. Yellow Bond A jumper cable that has been designated by the Signal Engineer to be an important part of the diverse bonding of common/single rail track circuit. It is coloured yellow or identified by yellow tape. Damage must be reported and repairs carried out as a matter of priority. Clearance Point The minimum distance from switches and crossings at which track circuits having the function of proving clearance may be terminated to ensure a passing clearance of at least 457mm between vehicles in all circumstances. Common Rail (CR) A track circuit arrangement where only one rail (the signal rail) is used with IRJs to separate the track circuits. The other rail (the common rail) is electrically continuous but is not used for traction return purposes. Cut Section A method of reducing the continuous length of a track circuit by the use of individual track circuits, each one controlling the same final TPR. These are indicated as one track circuit on the signalman's panel. Double Rail (DR) A track circuit arrangement where both rails are fitted with IRJs, or tuned zones are used to completely isolate a track circuit. Drop­away Time The time between the application of a shunt to the rails and the front contacts of track relay (TR) fully opening (see also Pick­up Time). Drop Shunt The maximum value of non­inductive resistance which, when placed across the rails, will cause the track relay to fully open its front contacts. Fishplate Metal plates for joining rails together. Frequency Rotation The sequential application of specified frequencies. Insulated Rail Joint (IRJ) A method of joining rails together whilst maintaining electrical insulation between them. Jointed Track Circuits Track circuits whose extremities are defined by the use of Insulated Rail Joints (IRJs). Jointless Track Circuits Track circuits whose extremities are defined by the use of tuned circuit techniques. The extreme limits of a jointless track circuit area are either defined by the use of IRJs or by the use of a tuned circuit between the rails.

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Joint Hopping Where fast moving short vehicles pass from one track circuit to the next, the difference between the pick­up and drop­away times can cause the vehicle to momentarily disappear. Jumper Cable Used to electrically connect, for track circuit or traction purposes, two pieces of rail that are not adjacent. Overlay Track Circuit A track circuit which can be superimposed over another, neither having any effect on the other and both operating independently. Pick­up Shunt The minimum value of resistance between the two running rails at which the track relay will just close its front contacts. Pick­up Time The time between the removal of a shunt from the rails and the front contacts of the track relay making (see also Drop­away Time). Plans For the definition of all types of Plans, see SDH E11. Selective Operation Operation of a portion of a track circuit by selection of the position of a set of points. Selective operation of track circuits is no longer permitted. Single Rail (SR) A track circuit arrangement where only one rail (the signal rail) is used with IRJs to separate the track circuits. The other rail (the common rail) is electrically continuous and is used for traction return purposes. Sleeper An item of wood, steel or concrete of standard dimensions, used to support and gauge the track (see Bearer and Timber). Spur A section of running rail required to be electrically common to a series bonded rail, but which is not itself in series. Stagger (Electrical) The phase or polarity difference between one track circuit and the next, or between the rails on either side of an IRJ within one track circuit. Stagger (Physical) Occurs where two IRJs in a pair of rails are not exactly opposite each other, thus creating a dead section between track circuits or within a track circuit. Switches & Crossings (S & C) Sections of track other than plain line. Tail Cable This is a cable which connects the lineside apparatus housing to the trackside equipment, but not direct to the running rails (see Track Cable). Timber An item of wood of non­standard dimensions, used to support the track in S & C areas (see Bearer and Sleeper).

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General Information on Track Circuits

Track Cable This is a cable which connects the track disconnection links/fuses or trackside equipment to the rails. Track Jumping Occurs when a fast moving vehicle passes over a very short track circuit (or a short arm of a longer track circuit) and fails to de­energise the track relay. Track Circuit Interrupter A device that detects the passage of a vehicle by causing a permanent disconnection within the track circuit until the device has been replaced. Transposition Joint An IRJ where transposition bonds are used to transpose the traction and/or track circuit rails. Catch or Trap Point A switch (ie. blades and tiebar only), inserted in sidings etc., to divert runaway rolling stock away from the main line, or on gradients to de­rail runaway wagons etc. Crossing The inter section of two tracks on the level. Often known as a diamond crossing due to the shape produced by the intersecting tracks. Not to be confused with the crossover.

Closure Panels Rail Joint

Heel Of Switch Rail Wing Rails Crossing Angle Switch Rails Switch Toes Closure Rails Stock Rails Crossing Nose Check Rail

Crossing Back

Figure B1

Switch and Crossing Terms Crossover A crossover consists of two points arranged to link parallel tracks. They are known as facing or trailing, depending on whether a train proceeding in its correct direction along the line can run directly over the facing crossover, or must reverse to cross the trailing crossover. Double Junction The point of junction of two double track routes. It comprises two turnouts and a crossing. Ladder Junction A form of junction eliminating the crossing.

4 Limitations

Where job titles are used within this Approved Code of Practice to reflect the anticipated functional splits of responsibility relevant to technical competence, they should not be interpreted as actual job titles. The specific split of B4 RAILTRACK

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responsibility will be governed by a contractual framework, to which reference should be made. Catalogue Numbers shown within this document are not directly controlled by Railtrack and as such, will not be maintained and kept up to date. Although every effort has been made to ensure that these were correct at the time of publication, it is therefore recommended that your supplier is contacted and a check is made with regard to the accuracy of these catalogue numbers prior to use. Where references are made to other documents, a comprehensive list of these will be contained within the "Ref" section of this document. The information appertaining to these references was correct as of Issue 13 of the Railtrack Catalogue of Railway Group Standards.

5 Introduction

5.1 The Purpose of Track Circuits The track circuit is a device designed to continuously prove the absence of a train from a given section of track; it cannot absolutely prove the presence of a train, since its designed failure mode is to give the same indication as if a train is present. By proving the absence of a train, a clear track circuit can be used to confirm that it is safe to set a route and permit a train to proceed. 5.2 Fundamental Design Principle A section of railway track is electrically defined by the provision of insulated rail joints (IRJs), or equivalent, in the rails at either end as shown in Figure B2. A source of electrical energy is connected, via a series impedance, across the rails at one end and a detector, which is receptive to the particular form of electrical energy, is connected across the rails at the other end.

Insulated Rail Joints

Transmitter (Feed)

Detector (Relay)

Figure B2

With no train within its boundaries, the detector senses the transmitted electrical energy and energises the repeater circuit. This conveys the absence of a train to the signalling system (ie. track circuit clear). A train within the track circuit will cause the rails to be short circuited such that the detector no longer sees sufficient electrical energy; it therefore changes state and informs the signalling system (ie. track circuit occupied). It can be seen that an electrical short circuit between the rails, caused other than by a train, or any disconnection within the circuit, will fail the track circuit and inform the signalling system that the track circuit is occupied. Such a circuit configuration incorporates a high degree of "fail safe"; it does, however, depend upon good electrical contact between the wheel sets of the train and the rails RAILTRACK B5

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General Information on Track Circuits

upon which they run. It also depends upon a continuous low impedance path between the steel tyres of each wheel via the connecting axle. Track circuits apply this basic principle in a variety of ways for various reasons. The source of electrical energy may be d.c., a.c. at power frequencies, a.c. at audio frequencies, or a series of impulses. The detector may be a simple relay, a more complex a.c. vane relay or a receiver tuned to a particular frequency or pattern of signals. Additional items may have to be added to overcome the problems arising from sharing the rails with heavy currents created by an electric traction system.

6 Electrical Behaviour of Railway Track

6.1 Ballast Resistance Ballast resistance is the resistance between the two rails of a track circuit and comprises of leakage between the rail fixings, sleepers and earth. The value of this resistance is dependent upon the condition of any insulations, cleanliness of the ballast and the prevailing weather conditions. The ballast resistance is inversely proportional to track circuit length and is expressed as ohm kilometres, typical values being in the range 2 to 10km. Lower values may be obtained in wet conditions with bad drainage and/or contamination with conductive materials. Higher values may be obtained in dry/clean conditions or during frosty weather. A reliable track circuit must therefore be able to operate over a wide variation of ballast resistance. Most simple explanations of track circuit operation portray ballast resistance as a single resistance connected between the rails as shown in Figure B3. Whilst such a representation is useful in explaining the simple behaviour of d.c. track circuits, it is important to understand that the model's limitations make it unsuitable to explain many of the more complex phenomena demonstrated by track circuits. For the types of track circuit used, the reactance of the ballast can be considered as negligible.

Rail Ballast Resistance

Rail

Figure B3

When considering other than the simple case, a more accurate model would represent the ballast resistance as a series of resistances between each rail and earth as shown in Figure B4. Although there is a further component of resistance between the rails independent of earth, it is high compared to the rail­ earth resistance and can be discounted for most calculations.

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Rail

Earth

Rail

Figure B4

6.2 Rail Impedance The d.c. resistance of rail is very low, around 0.035/km, although this is increased to approximately 0.25/km by the relatively higher resistance of galvanised iron bonds in jointed track. The inductance of rail can raise the overall impedance per rail from approximately 0.3/km (50Hz) to, in the case of reed track circuits, 2.5/km (400Hz) and for TI21 track circuits, 10/km (2kHz). These impedance values may be increased further by large traction currents, due to the rail being driven toward saturation. When considering a.c. track circuits, rail inductance must be taken into account by application of the further complex model including rail inductance as shown in Figure B5. Although of little consequence at power frequencies, audio frequency track circuits exhibit a steep decline in rail voltage as distance from the transmitter increases. Since the ballast resistance is now distributed throughout the length, detailed calculation requires the use of hyperbolic functions. These effects can usually be ignored when considering the operation of a.c. power frequency track circuits, where rail voltage can be expected to decline very little between the feed and relay ends.

Rail

Earth

Rail

Figure B5

6.3 Rail to Rail Capacitance Although an even more complete picture would include rail­to­rail capacitance, this is very small and of marginal significance relative to track circuit operation at audio frequencies. 6.4 Workable Lengths of Track Circuits It can be seen that the workable length of a track circuit is limited by three factors:

· ·

the declining value of ballast resistance; the increasing value of rail impedance;

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General Information on Track Circuits

·

Immunisation / Electrification requirements, including electromagnetic compatibility with trains.

As the various types of track circuit feed/transmitter produce differing power outputs, and as rail impedance is frequency related, it follows that the maximum workable length will vary with design type and with the minimum ballast resistance at which the track circuit is expected to remain functional.

7 Operation and Adjustment of the Simple Track Circuit

Consider the simple d.c. track circuit depicted in Figure B6.

Feed Resistance

Cable Resistance Rail Train Shunt Ballast Resistance Rail

Cable Resistance TR

Cable Resistance

Cable Resistance

Figure B6

7.1 Track Circuit Clear The ballast resistance forms an additional load in parallel with the relay. As the ballast resistance falls due to wet weather, the current drawn from the feed increases. This will cause the voltage across the feed resistor to increase, so reducing the rail and relay voltages. If this reduction causes the relay voltage to fall below the relay pick­up value, the track circuit will not clear after an occupying train has departed. A further reduction of the relay voltage to below relay drop­away value will fail the track to the occupied state without the passage of a train. Reducing the value of feed resistance has the effect of increasing the current fed into the rails and raising the rail/relay voltage. Long feed end leads insert additional non­adjustable feed resistance and thereby reduce the effectiveness of the adjustable feed resistance. Long relay end leads reduce the ratio of relay voltage to rail voltage by potential divider action; the effect is to cause the track circuit to indicate occupied at a higher ballast resistance. It therefore imposes a shorter maximum workable length. 7.2 Track Circuit Occupied When the track circuit is occupied by a train, a short circuit current will flow from the feed end equipment, which is limited by the value of the feed resistance and the characteristics of the feed end equipment itself. The feed end equipment is designed to cope with this worst case power dissipation. The train shunt resistance is in parallel with the ballast resistance. With any given value of feed resistance, the relay will operate at particular values of combined ballast/train shunt resistance. Thus, higher ballast resistance will require a lower value of train shunt resistance to operate the relay and vice versa.

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The minimum permitted drop shunt resistance is 0.5 (0.3 on certain impedance bond track circuits). During very dry weather or severe frost conditions, the ballast resistance increases towards its natural maximum and will offer only a small contribution towards the overall shunt. Thus, when a 0.5 (0.3) shunt is placed across the rails, it must still reduce the relay voltage to below drop­away value. It should also be noted that the track relay is dropped by short circuit rather than disconnection. Therefore, the drop­away time of the relay is increased due to the inductive circuit prolonging the decay of the coil current. 7.3 Principles of Basic Adjustment The difficulty with adjusting track circuits (where such adjustment is provided) is knowing the prevailing value of ballast resistance. Details entered on the track circuit record card provide a useful history. These vary with track circuit type and the appropriate Code of Practice within the Track Circuit Handbook should be consulted. Assuming average conditions, the feed resistance is adjusted to obtain a relay voltage in the range 25% to 75% above the pick­up value whilst maintaining the drop shunt resistance at a value greater than the minimum required. If the track circuit fails due to wet weather, it may be possible to remedy the situation by reducing the feed resistance. It is important that the track circuit is re­tested after it has dried out.

8 Train Shunt Imperfection

The energy seen by the relay with a train on the track circuit will depend upon the resistive value of the train shunt (see Figure B6). This energy will be zero only when the train shunt is zero. Whilst the ohmic resistance of an axle and wheels is virtually zero, there are a number of factors that can make the effective train shunt much higher. Since some factors are track based, whilst others are vehicle specific, the precise mixture of factors applying to a particular vehicle at a particular place can be very variable. 8.1 Rust Films Light rust film on the rail head and/or tyre tends to act as a semi­conductor, in that it exhibits high resistance until the voltage exceeds a particular threshold value when it breaks down completely. The breakdown voltage rises in sympathy with the extent of the contamination; very heavy rust films, resulting from prolonged disuse, render many track circuit designs incapable of detecting vehicles. Figure B7 gives an approximate characteristic of such films.

Damp Light Rust Dry Light Rust Heavy Rust Or Leaf Residue

Current

Very Good

Good

Poor

Bad

0.01V

0.05V

0.1V Voltage

0.3V

0.6V - 200V

Figure B7

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The mechanical strength of light rust films is much reduced by the presence of moisture when the contaminant tends to be squeezed out from the wheel­rail contact patch and doesn't cause any shunting problems. Therefore, lightly rusted rails will only be a problem when dry. This problem is most severe when conditions are:

· ·

showery weather accompanied by drying wind; or prolonged periods without trains.

Special precautions need to be taken after relaying operations, when track circuits must not be restored to full operation until a reasonable surface has been created. 8.2 Leaf Residue This problem is confined to particular areas where the extent of lineside afforestation is significant. It is also limited to autumn when trees are shedding their leaves. Leaves are drawn into the wheel­rail interface by the passage of a train, where they are squashed into a pulp which contaminates both rail and tyre. The severity of this problem in particular years is connected to the general weather situation. In simple terms, reasonably dry weather with little wind will cause the leaves to fall gradually over a long time period and to be reasonably sap free when they do fall. Conversely, gale conditions will lead to a sudden massive fall of sap laden leaves. It is the latter situation which gives rise to the worst conditions. In terms of track circuit operation, the electrical characteristics of severe leaf residue are similar to very heavy rust. Fortunately, the sites suffering such problems are generally known and special arrangements can be made. 8.3 Coal Dust and Sand Problems with coal dust on the rail head tend to be confined to colliery areas, where coal deposited on the wagon chassis after loading/unloading is subsequently shaken off. Sand contamination is usually associated with slow moving locomotives using their sanders excessively. In each case, the effect is similar to heavy rust films. 8.4 Composition Tread Brake Blocks Certain types of rolling stock are fitted with a composite type of tread brake block instead of the traditional cast iron variety, the intention being to improve brake performance. This is found to deposit a contaminant film on the steel tyre, which tends to insulate the train from the rails. 8.5 Tread and Disc Brakes When considering the electrical contact between two pieces of metal separated by a thin film of insulation, it can be appreciated that surface roughness of the metal can permit high spots to penetrate the film. Where this occurs, the insulation will be ineffective. Tread brakes cause the tyres to be roughened at each brake application, whereas disc brakes allow the tyres to be rolled into a very smooth surface condition. This can be observed visually as tread braked tyres have a matt appearance, whilst disc braked tyres show a mirror­like quality. Therefore, tread braked vehicles provide a better train shunt than disc braked vehicles. 8.6 Axle Weight and Suspension Design The pressure applied to any contaminant film is proportional to the downward force of the wheel on the rail and this is proportional to vehicle axle weight.

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In practice, wheels do not roll smoothly and friction free. There is a guidance force continually pulling the wheelset into the correct trajectory and this guidance force is associated with microscopic slippage between wheel and rail. Advances in bogie design have tended to reduce this guidance force and slippage, giving a smoother ride for the passenger as well as reducing the wear rate of both rail and tyre. Unfortunately, these qualities reduce the ability of the tyres to penetrate any film, as well as reducing their ability to clean the rail by abrasion. 8.7 Track Geometry Vehicle guidance force and wheel rail slippage are increased in curved track. Therefore, train shunt will be improved when the vehicles are travelling on curved track.

9 Detection of "Lightweight" Vehicles

If all rails and tyres were clean and wheel­rail contact was perfect, any type of vehicle would satisfactorily operate any type of track circuit. However, secondary lines in particular have suffered a fall in traffic leading to regular formation of light rust films. At the same time, the vehicles using such lines have been increasingly of the modern DMU variety, which magnify the train shunt difficulties because of their suspension design, brake type, weight (which, although still heavy, is relatively light) and small number of vehicles in a train. When a vehicle is static on a light rust film, the track circuit voltage will usually break it down and the track circuit will occupy. This is because the track clear rail voltage is higher than the film breakdown voltage. However, when that vehicle is moving, the wheels are continually rolling onto new film which requires to be repeatedly broken down. Consider the following sequence of events: When a wheel first enters the track circuit, the track clear rail voltage is presented across the film. The film breaks down resulting in the rail voltage collapsing towards zero. As the wheel moves on to new surface, there is insufficient voltage available to break through the new film. The train shunt is removed and the rail voltage rises towards the clear value. When the rail voltage attains the breakdown level, the film is punctured, the train shunt re­applies and the rail voltage once again plummets toward zero. The result is a high frequency noise voltage across the rails which can be observed with a suitably sensitive instrument. Where the threshold breakdown voltage is less than the rail voltage at which the relay drops away, the noise will not result in track circuit malfunction. This parameter is used to assess the performance of various track circuit types relative to their ability to detect lightweight vehicles. To assist vehicles to shunt track circuits, a device known as the "Track Circuit Assister" has been fitted to modern diesel multiple units.

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10 Track Circuit Insulations

10.1 Insulated Rail Joints Insulated rail joints (IRJs) are required to join rails together mechanically but not electrically. The Permanent Way Engineer is responsible for the installation and maintenance of all IRJs. 10.2 Point Equipment Apart from the IRJs, used to electrically separate sections of rail, the reliable operation of track circuits requires the provision of other insulations in particular circumstances. Any direct metallic connection between the two rails will be interpreted as a train and will cause the track circuit to fail occupied. At a set of points, there are many of these connections, which therefore need to be fitted with insulations, as shown in Figure B8, which is a typical example; there are, however, some regional variations.

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Insulation B

Insulation

D

A C E Insulation

A Soleplate The soleplate is formed from two metal plates secured together by a bolted connection at an intermediate position between the rails, which includes insulated ferrules, washers and plates to maintain electrical separation. Where the soleplate is extended to one side, as required for point machine operation, a second insulated connection is provided between the point machine and the nearest rail. B Permanent Way Stretcher Bars These connect the two point switches together and are formed from two separate pieces connected together with two bolts. The bolted connection includes insulation ferrules, washers and plates to maintain electrical separation. C FPL Stretcher Bar Insulation ferrules, washers and plates are fitted where the stretcher bar is connected to one of the point switch blades; usually that furthest from the drive mechanism. The design is such that the insulation can be fitted at either end of the stretcher bar, but should not be fitted at both ends. D Point Drive Rod Insulation is provided either separately, or is incorporated into the drive rod jaw connection onto the point machine. E Lock & Detector Rods Insulated bushes are fitted where the screwed end connections are attached to the switch extension pieces.

Figure B8

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General Information on Track Circuits

10.3 Concrete Sleepers Early forms of concrete sleeper were fitted with chairs for bullhead rail in similar fashion to those fitted to timber sleepers. The chair was usually secured to the sleeper with a through bolt from the underside. These did not present any widespread problem since track circuits were not common in the rural areas, where concrete sleepers were seen to be advantageous. Although short track circuits can be made to work over such sleepers, the ballast resistance is usually quite low and subject to more severe weather related swings. It is also now known that damp concrete behaves as an electrochemical secondary cell which can give rise to residual voltage problems with d.c. track circuits. Modern concrete sleepers incorporate a rubber pad under the rail foot and moulded insulations where the fixings bear on the top of the foot, as shown in Figure B9. The effect is to increase ballast resistance to levels significantly higher than those obtained with timber sleepers. However, the insulations do erode due to the vibration of passing traffic and, consequently require periodical replacement. Lack of attention to insulation usually results in gradual degradation of the ballast resistance rather than sudden failure.

Front Arch

Insulation

Rail Pad Rail Foot

Centre Leg

Heelseat

Rear Arch

Figure B9

10.4 Steel Sleepers Steel sleepers are equipped with insulations similar to modern concrete sleepers and, provided they are subject to an effective preventative maintenance programme, track circuits will operate satisfactorily. However, as the sleeper is in more intimate electrical contact with general earth, much higher levels of track circuit unreliability will result from poor insulation than is the case with modern concrete sleepers.

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11 Bonding

Bonding describes the means by which the individual components of the railway track are connected together electrically for track circuit purposes. The term also includes the additional electrical connections necessary for the proper operation of electric traction. Symbols used on bonding plans are shown in Part C and various terms are explained in Section 3. Refer also to GK/RT0252. 11.1 Series and Parallel Bonding In order for a track circuit to fail safe (to show occupied) in the event of a bonding disconnection, it is necessary to bond all elements of the track circuit in series. However, in S & C areas, it may not be physically possible to arrange total series bonding of both rails. Examples of series and parallel bonding are shown in Figure B10. Provided that a spur is very short, it is permissible to bond it in parallel without additional safeguard. However, where the spur is long, or in other cases where necessary, parallel bonding may be resorted to provided that steps are taken to ensure that vehicles are not lost due to disconnection of part of the parallel system. This is achieved by creating a mesh of alternative diverse bonding paths between parallel elements, and clearly identifying the associated bonds by their yellow colour. It is necessary to ensure that such yellow bonds are repaired quickly before other bonds in the mesh have time to fail in a manner likely to cause an unsafe failure. Because of the additional complication of significant rail impedance with parallel bonding, audio frequency track circuits are generally unsuitable in all but the simplest of pointwork.

Track Feed

Track Relay Preferred Series Bonding Track Relay Track Feed

Non-preffered Parallel Bonding

Figure B10

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General Information on Track Circuits

11.2 Double and Single Rail Track Circuit Bonding Double rail track circuit arrangements have both rails fitted with IRJs to completely isolate a track circuit. Impedance bonds are used when a traction current return path is required. IRJs and impedance bonds are not required with Jointless Track Circuits. Single rail track circuit arrangements have only one rail fitted with IRJs to separate the track circuits. The other rail is electrically continuous. If this continuous rail is used for traction return purposes, the bonding arrangement is called Single Rail Bonding. If this continuous rail is not used for traction return purposes, the bonding arrangement is called Common Rail Bonding. Whilst some designs of track circuit can be used in either single or double rail mode, others are limited to double rail application. In some S & C areas and certain electric traction areas, it is necessary for one or more adjacent track circuit to share one common rail. This arrangement can lead to unsafe failure modes unless special steps are taken to ensure that elements of the common rail cannot become isolated from the remainder. This is achieved by creating a mesh of alternative diverse bonding paths and marking the associated bonds yellow as for the previous parallel bonding case. 11.3 Track Circuit Interrupters Track circuit interrupters are used at trap or run­back catch points on lines which are track circuited. The device is designed to interrupt the track circuit in the event of a rail vehicle leaving the track. This prevents automatic re­ energisation of the track circuit after the removal of the train shunt. The interrupter is a metal device attached to the four foot side of the stock rail and usually insulated from it. It comprises a main body, a narrow neck and a head which is adjacent to the running edge and designed to break off when a rail vehicle passes over it. Connections are made to the head and the body such that electrical continuity is provided between them until the interrupter is broken. The arrangement is shown in Figure B11. The interrupter is fixed within the track circuit to the stock rail (as shown in Figure B12). It is not fixed to the switch rail.

Bonding Connection Points

Figure B11

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Note: In all cases, the interrupter is fixed to the stock rail (as shown in Figure B12). It must not be fixed to the switch rail.

Stock Rail Correct Position

Incorrect Position

Switch Rail

Figure B12

12 Mutual Interference Between Track Circuits

It is important to realise that where track circuits are connected together by a common rail, and detectors are used that are unable to discriminate between their own and other track circuit feeds, a degree of mutual interference between such track circuits is inevitable. This condition may be introduced by design (single rail track circuits on electrified lines) or by failure (IRJ failure of double rail track circuits). The simplest way to describe mutual interference is to use the example of two d.c. single rail track circuits as shown in Figure B13 and Figure B14. It will be realised that this model also equates to a double rail insulated track circuit with a failed IRJ. Figure B13 shows the equivalent circuit in track circuit type format, whilst Figure B14 converts it to a standard electrical format for easier presentation of cause and effect. Consider the circuit in Figure B14 under conditions where VFB feed supply is disconnected. Clearly, a voltage will appear across RRB as a result of VFA, the value of which will depend on circuit parameters. The extent to which this voltage is of concern depends upon its value relative to the operating values of the relay. Provided that the bonding remains intact, an unsafe failure cannot arise from the mutual interference; either both track circuits will fail right side (occupied) or they will both show occupied when either one of them is legitimately occupied. However, there is the possibility of a wrong side failure where a bonding disconnection occurs. It is not appropriate to explain all possible scenarios here; the possibility is mentioned simply to convey the fact that some track circuit defects can be exceedingly difficult to understand and explain. Certain constraints are applied to various track circuit designs in order to limit the possibility of wrong side failure. Therefore, the design constraints described in the Track Circuit Handbook shall not be breached without expert advice.

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General Information on Track Circuits

Common Rail

TC A

TC B

RRA

RFA

RFB

RRB

RCA

VFA

VFB

RCB

RSA Earth

RSB

Figure B13

Notes for Figure B13 and Figure B14: TC"A" OPEN CIRCUIT FEED VOLTAGE FEED RESISTANCE RELAY RESISTANCE SIGNAL RAIL EARTH RESISTANCE COMMON RAIL EARTH RESISTANCE VFA RFA RRA RSA RCA TC"B" VFB RFB RRB RSB RCB

Common Rail

Further Track Circuits

RCA RFA RRA VFA RSA Earth

RCB RRB RFB

VFB RSB

Figure B14

13 Detection of Rail Breaks

Where rails are series bonded, a completely broken rail will be immediately detected as a right side track circuit failure (ie. occupied). Where the rails are not series bonded, a broken rail will not be detected by the track circuit.

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14

Jointless Track Circuits

Insulated rail joints can be expensive both to install and to maintain, especially on tracks subjected to high speed, high axle weight traffic or where there is an intensive service. The use of audio frequencies permits the physical limits of an individual track circuit to be defined by tuned short circuits between the rails rather than by insulation in the rails themselves. Consider two jointless track circuits abutting at a tuned zone as shown in Figure B15. Non­track mounted equipment has been omitted for clarity.

Tuned Zone

Feed F1

Tuning Unit F1

Tuning Unit F2

Feed F2

Figure B15

The tuned zone comprises a measured length of track with a tuning unit across the rails at each extremity. The track circuits operate at different audio frequencies and each tuning unit is designed to its own track frequency, such that the following criteria are obeyed: a) Consider frequency F1: The F2 tuning unit behaves as a short circuit between the rails, due to series resonance of its inductive and capacitive components. The F1 tuning unit tunes the two rails (inductive) and the F2 tuning unit short circuit to parallel resonance, thus presenting a significant impedance to frequency F1. b) Consider frequency F2: The F1 tuning unit behaves as a short circuit between the rails, due to series resonance of its inductive and capacitive components. The F2 tuning unit tunes the two rails (inductive) and the F1 tuning unit short circuit to parallel resonance, thus presenting a significant impedance to frequency F2. A wheelset proceeding along track circuit F1 will shunt the track circuit, but when it enters the tuned zone its effectiveness will reduce until, having passed tuning unit F2 (short circuit at frequency F1), it will no longer shunt track circuit F1. Similarly, the wheelset would not shunt track circuit F2 as long as it remained on track circuit F1, due to tuning unit F1 presenting a short circuit to frequency F2. As the wheelset passes F1 tuning unit, it commences to shunt frequency F2, becoming more effective as it progresses towards the F2 tuning unit and beyond into F2 track circuit proper.

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General Information on Track Circuits

By careful design of components, it is possible to arrange a short overlap in the centre of the tuned zone where both track circuits are effectively shunted. Since the design of individual tuning units must take account of both frequencies, it is necessary to specify the exact frequencies involved. Such equipment is therefore produced for a fixed set of frequencies and those frequencies are used in pairs alternately along the track.

15 Track Circuits and Electric Traction

Beyond the boundaries of electrified areas, track circuit type and configuration can be selected on the basis of train detection and economic criteria alone. However, track circuit arrangements in electrified areas are constrained by the need to ensure safe and reliable operation of both signalling and traction systems. This means that the track circuit must be immune to both false operation and damage by the flow of traction currents through the rails. Parallel tracks are cross-bonded at regular intervals, such that the traction return current from an individual train will have a number of different parallel paths back to the supply. This minimises the impedance to the traction supply and hence the volt drop, whilst it also limits the amount of current which can flow through an individual track circuit. Although permitted track circuits will be inherently immune to false operation (wrong side failure) from the presence of traction currents flowing in the rails, in some circumstances these can be of a magnitude sufficient to cause damage to equipment, or right side failure of the track circuit. The levels of traction current that the track circuit is subjected to can generally be sufficiently limited by well maintained bonding, track circuit length restrictions (single rail track circuits) and balance of traction currents between rails (double rail track circuits). Specific restrictions related to interference are contained within the individual track circuit type Codes of Practice. 15.1 D.C. Electrified Areas In d.c. electrified areas, the relatively low supply voltage results in high currents returning to the sub-stations via the running rails. In order to minimise voltage drop in the d.c. traction supply, wherever possible, all running rails are used for the return of traction currents and therefore double rail track circuits are used. However, in S&C areas, it is not usually possible to bond the track in double rail form, therefore single rail track circuits have to be installed. Traditionally, all track circuits in d.c. electrified areas, were operated with 50Hz a.c. current, using phase sensitive vane relays. Double rail track circuits, with impedance bonds providing traction current continuity, were provided on plain line and single rail track circuits in S&C areas. More recently, jointless modulated audio frequency track circuits have been introduced, reducing the number of IRJs and impedance bonds required in plain line areas.

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15.2 A.C. Electrified Areas In present 25kV a.c. electrified areas, traction currents are lower than in d.c. systems and in most cases, single rail traction return is sufficient for electrification purposes. Increased traffic levels and alternative feeding arrangements, may however, increase the need for both running rails to be used for traction return. Traditionally, all track circuits in a.c. electrified areas, were operated with d.c. current, although feed and relay components are specifically modified to provide protection from damage and immunity to interference. 15.3 Dual Electrified Areas Where tracks may be subject to the flow of both a.c. and d.c. traction currents, the choice of track circuits is limited to those that are immune to both and do not use frequencies (including harmonics) contained in the traction supply. 15.4 Single Rail Track Circuits Where traction return current flows through a single rail track circuit, the majority of the current will flow in the traction rail, resulting in a voltage drop along it's length. This voltage drop is proportional to the current, the track circuit length and the impedance of the rail. With a train shunt applied toward the feed end of the track circuit, this voltage drop can be presented across the signal rail and track receiver in series. Dependent upon the relative impedance of the signal rail and the receiver at the frequencies of interest, a proportion of this voltage will be applied across the receiver. If the traction supply contains some voltage disturbance at a frequency to which the track circuit is sensitive, then this will be conducted through trains and flow as current through the running rails. If this is of sufficient magnitude, form and duration, then with a train shunt at the feed end, a wrong side failure could occur. In addition to conducting the voltage ripple present on the traction supply, modern traction units employing active control methods (such as three phase drives) can actively generate currents at other frequencies and superimpose them onto the supply. Whilst the traction control systems can be designed so as to avoid critical frequencies as far as possible, some interference content at frequencies used by track circuits may be produced. Depending upon the type of traction unit, the magnitude of this interference content may be limited by the use of an Interference Current Monitor Unit (ICMU) on the train, which will isolate the traction unit from the supply if sufficient interference flowing through the train, is detected. These ICMUs however, take a finite time to operate, and whilst the operate delay, due to the use of slow operating repeat relays, is generally sufficient to cope with transient interference, it may be necessary to modify the track circuits before the train can reliably operate.

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General Information on Track Circuits

15.5 Double Rail Track Circuits Where both running rails are used for traction current return, the electrification arrangements, using impedance bonds, are designed to keep the currents flowing in each rail balanced. Under such conditions, any interference content within the traction current should similarly be balanced and little or no interference applied to the receiver. However, due to a number of reasons, interference currents flowing through the track circuit may be, or become, imbalanced:

· · · · · · ·

presence of check rails; track curves; earthing of one rail; bonding differences; asymmetric position of conductor rail / catenary; broken rails; disconnected impedance bond sideleads

When the track circuit becomes unbalanced any interference in the traction return current due either to disturbances in the supply, or generated by traction units, will result in interference being presented to the receiver. The magnitude of this interference is largely independent of the length of the track circuit, but is proportional to the imbalance of currents flowing through the receiver end of the track circuit (either an impedance bond or tuned zone). Therefore, with a train occupying the track circuit, interference can be applied to the track receiver, which if of sufficient magnitude, form and duration, will cause a wrong side failure of the track circuit. 15.6 Rolling Stock Compatibility Means of providing compatibility between rolling stock and track circuits, without the use of ICMUs, is preferable and modern traction units may be acceptable for use with the existing track circuits, if it can be demonstrated that the predictable level of interference which may be generated, is insufficient to interfere with correct track circuit operation. Such an assessment will need to make reasonable assumptions as to the proportion of traction current that can flow through an individual track circuit, the resulting magnitude of interference which will be presented to the track receiver and the minimum response time of the receiver and interlocking. Therefore the validity of such assessments relies upon the following:

· · · · ·

cross bonding between parallel tracks; track circuit length limitations; prevention and detection of imbalance; integrity of rails and bonds; operating times.

CAUTION: Although general precautions and limits that provide compatibility between rolling stock and track circuits, have been included in the Train Detection Handbook Codes of Practice, these are not comprehensive and special conditions may apply to certain routes to permit the operation of rolling stock. Where new types of rolling stock are to be introduced, existing constraints will require reassessment, as to their adequacy.

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16 Impedance Bonds

16.1 Operation Impedance bonds are devices which allow traction current (d.c. or a.c.) to pass through, whilst limiting the track circuit current. They are necessary wherever double rail traction return and IRJ dependent track circuits coexist. An impedance bond is configured to provide a very low impedance path to double rail a.c. or d.c. traction return currents (typically less than 0.4m per coil) whilst presenting a high enough a.c. impedance between the rails (typically greater than 15) to allow the operation of track circuits. It also provides a centre connection for cross bonding, which minimises the passage of track circuit current between circuit currents. The winding connected between the rails is comprised of heavy gauge copper, fitted with a centre tap connection and wound on a heavy iron core. Provided that each running rail carries equal amounts of traction return current, the current from each rail passes in opposite directions through the coil from the rail to the centre tap connection. The net flux in the iron circuit will be zero and the impedance to traction current (d.c. or a.c.) will be very small, as shown in Figure B16.

IRJ

1/2 Traction Current

IRJ

1/2 Traction Current

Cross Bond

Cross Bond

Track Transmitter

Track Receiver

Figure B16

The a.c. track circuit current attempts to flow between the two rails and is therefore in the same direction through the two halves of the winding, resulting in the track circuit current seeing a larger, albeit still relatively small, impedance. Track­to­track cross bonding on double rail track circuits must be provided via the centre taps of impedance bonds on electrified lines, as shown in Figure B17.

Cross Bonds

Figure B17 RAILTRACK B23

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General Information on Track Circuits

16.2 Auxilary Winding The impedance available from the simple impedance bond remains a handicap. It is therefore usual to enhance the impedance by parallel resonance of the traction winding, use being made of a step­up (approximately 50:1) transformer to reduce the value of the necessary capacitance to realistic levels. Another solution is to connect the resonating winding to form an auto transformer, refer to 16.2.2. 16.2.1 Resonated Impedance Bonds The induction of the traction winding is tuned to resonance at or near the track circuit operating frequency by use of a parallel capacitor, which raises the rail to rail impedance at the track circuit frequency, and thereby reduces the bond's effect on the track circuit. For power frequency track circuits (eg. 50 Hz), the value of capacitance required to attain resonance is reduced to an achievable magnitude, by applying the capacitance via an auxiliary winding, as shown in Figure B18.

IRJ

Auxiliary Flux Winding

To Next Bond Or Cross Bonding

IRJ

Figure B18

The value of capacitance required to achieve resonance depends on the following: a) Traction winding inductance, which may differ between designs. The capacitance required will vary inversely to the inductance. b) Auxiliary turns ratio, which may differ between designs. The capacitance required will vary inversely as the square of the turns ratio. c) Track circuit frequency, where the capacitance required will vary inversely as the square of the frequency. Resonated impedance bonds are used at the feed and relay ends of jointed audio frequency track circuits and for all intermediate bonds associated with traction cross bonding.

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16.2.2 Auto Coupled Impedance Bonds The method used to couple the feed and relay ends of certain designs of track circuit into the track as shown in Figure B19. At the feed end, the reduced voltage appearing across the the traction winding is applied to the rails whilst at the relay end, the current from the track circuit passing through the traction winding is usefully employed to drive the relay.

IRJ

OR To Next Bond Or Cross Bonding To Rails To Track Relay Or Feed

IRJ To Track Relay Or Feed

Figure B19 A double rail A.C. track circuit with auto­coupled impedance bonds is shown in Figure B20.

Resonant Bond

Control Local

110V 110V

Figure B20

If the traction current in each rail is not equal, the imbalance results in a net flux in the iron circuit, and if that flux is sufficient to saturate the iron core, the track circuit current will be presented with a short circuit. It is therefore important to make the bond as tolerant as possible of traction current imbalance and this is done by creating an air gap in the magnetic circuit. Such bonds will tolerate 20% imbalance before saturation.

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Part C Schematic Symbols

1 Introduction

The schematic symbols described here apply to bonding plans. Symbols depicting track circuits on signalling plans are to be in accordance with GK/RT0004.

2 Drawing Symbols on Bonding Plans

2.1 Bonding Bonding plans must show connections which require traction voltage warning labels, as shown in Part E. Symbol Description

Electrified lines: Rails bonded, but not track circuited.

Electrified lines: Only one rail continuity bonded.

Non-electrified lines (In electrified areas): Rails not bonded.

Single rail traction return: In non-electrified areas one rail shall be drawn bold, this shall be the series rail for CR Bonding and the positive or BX rail for DRDS Bonding. Signal rail insulated by IRJs Continuous traction return rail

Stainless steel strip on rails.

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General Information on Track Circuits

Symbol

Description

Insulating rail joints: Separate track circuits on both sides.

Insulating rail joints: Track circuit on left, none on right.

Insulating rail joints: Track circuit on right, none on left.

Insulating rail joints: Between different sections of the same track circuit.

Standard jumper bond.

Traction bond.

Yellow bond.

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Symbol

Description

Structure bond.

Signal engineering equipment to rail bond.

Structure to Earth Wire.

Rail to rail bond (cross bonds) - (one example).

Return conductor or earth wire to rail bond.

Track circuit interrupter.

Connections for dc track circuits.

Connections for ac track circuits.

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General Information on Track Circuits

Symbol

Description

Connections for HVI track circuits.

Guard boarding

The provision of guard boarding will be indicated by a thin line on whichever side of the conductor rail it is required. A suitable note may be added if required.

Insulated buffer stops.

Non-insulated buffer stops.

Insulated points.

Non-insulated points.

2.2 Track Circuit Actuator Interference Detector (TCAID)

TCAID-N or TCAID (MC)

TCAID-D, detection to the right

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2.3 Impedance Bonds If an impedance bond contains an internal resonating capacitor, the symbol must be shown filled in.

Symbol Description

Double rail to double rail track circuits.

Double rail to single rail track circuits.

Double rail track circuits to non-track circuited line.

Intermediate impedance bond.

Cross Bonds (Track to track bonds): Using impedance bonds in double rail areas.

Tuned impedance bond.

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General Information on Track Circuits

2.4 Symbols For TI21 Jointless Track Circuits

Symbol

Description

Tuned zone with a transmitter and a receiver.

Transmitter of centre fed track circuit at an end tuning unit (ETU).

Receiver at an IRJ with an end tuning unit (ETU).

Low power: Show at transmitter only.

Example of a TI21 track circuit bonding plan.

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2.5 Symbols For Reed Track Circuits

Symbol

Description

Transmitter.

Receiver.

Intermediate simple loop (loop symbol points towards TX).

Compound loop (loop symbol points towards TX).

Example of a jointed reed track circuit bonding plan electrified.

Example of a jointless reed track circuit bonding plan.

Note: Track circuit frequency is indicated in ( ) brackets following the track circuit name.

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General Information on Track Circuits

3 Traction Return Bonding Symbols

Separate Traction Return Bonding Plans are only used on the former Southern Region.

Symbol

Description

Running rail bonded at each rail joint for dc electric traction.

Insulated rail joint.

Resonating bond.

Impedance bond.

Track circuit cut section.

To specify that more than one bond is required, indicate as shown.

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Symbol

Description

Single protective boarding.

Double protective boarding.

Insulated rail joint and continuity cable to eliminate magnetisation of points.

Aluminium advance plate:

Only installed for attachment of traction return bonds in areas of single rail traction return.

Cable Identification Codes a c d f g h j Single 500mm sheathed copper cable (soldered lugs) or single 800mm sheathed aluminium cable (crimped aluminium or Cadweld aluminium lug). Single 161mm sheathed copper cable (gas weld heads). Single 161mm sheathed copper cable (soldered lugs) or single 240mm sheathed aluminium cable (Cadweld aluminium or copper lug or crimped aluminium lug). Single 161mm bare copper cable (gas weld heads) or single 150mm aluminium cable (crimped 20 bi-metal bond heads). Single 161mm copper cable (soldered 20 copper bond heads). Single 161mm sheathed cable (one gas weld head and one soldered lug). Single 161mm sheathed cable (one soldered lug and one soldered 20 copper bond head) or single 150mm sheathed aluminium cable (one crimped 20 bi-metal bond head and one crimped aluminium lug). Single 1,000mm sheathed aluminium cable. Single 630mm sheathed copper cable.

m n N

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General Information on Track Circuits

4 Engineer's Scale Diagrams

4.1 General Symbols These symbols are to be used on the 1:100 and 1:200 scale diagrams when requesting IRJs and point insulations to be installed by the Permanent Way Engineer. The symbols are to be coloured red on plans returned to the Permanent Way Engineer. Note: On Permanent Way Engineer's Plans, dimensions are to the inside edges of rails.

Symbol Insulated rail joint required. Description

Insulated soleplate and stretcher bars required (position of insulation to be shown).

Drilling of insulated soleplate for facing point lock required, to MD 82017 (position of insulation to be shown).

Extended sleepers and soleplate required for the installation of combined type machines with left hand drive (show in reverse for right hand drive). Standard facing points (not clamp locks), drilled to BRS-SM 318.

Extended sleepers and soleplate required for the installation of combined type machine. Right hand drive for single or double slips (not clamp locks), drilled to BRS-SM 319.

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Symbol

Description

Extended sleepers and soleplate required for the installation of combined type machine. Left hand drive for single or double slips (not clamp locks), drilled to BRS-SM 320.

Indicates switch rail, stock rail and soleplate to be pre-drilled for hydraulic clamp locks with multiple drives and soleplate, in accordance with BRS-SM 2200, 2228, 2240, 2244 or 2260, as appropriate. If concrete sleepers are to be used, they are required to be drilled in accordance with BRS-SM 622.

Stainless steel strip welded to rails required.

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Part D Planning and Design

1 Introduction

The principles laid down here apply to the planning, layout and design of all types of track circuits and track circuit bonding. Special requirements for individual types of track circuit are given in subsequent Codes of Practice within the Track Circuit Handbook. Signalling design requirements are contained in GK/RT0201. Many of the parameters affecting track circuit design are related to the physical and electrical characteristics of the trains operating over the track circuits. Dimensions of track sections which are critical for achieving safe and reliable detection are contained in GK/RT0011 Appendix A. If the accuracy quoted cannot be attained, dimensions should be rounded up unless otherwise stated (ie. if a maximum is given). For a description of terms and definitions used in track circuit design and operation, see Part B. For details of symbols used on scheme plans and bonding plans, see Part C.

2 Responsibilities for Bonding Design

2.1 General Bonding requirements are contained in GK/RT0252. 2.2 Non­electrified Lines The design of all track circuit bonding on non­electrified lines is the responsibility of the Signal Engineer. This requires the production of detailed scale bonding plans for all track circuiting in switch & crossing work, usually based on the Permanent Way Engineer's track layout plan. On plain line a detailed bonding plan need not be produced, as long as sufficient detail of feed and relay leads is provided in lineside apparatus housing diagrams. 2.3 Electrified Lines Both Signal and Electric Traction Engineers require connections to the running rails, so compatibility between them is essential. In addition, there are a number of connections upon which there is common reliance. It is therefore necessary to have common plans/records that show in detail the track bonding arrangements. There must be agreement between both parties before any new work or alterations are carried out. Design Standards are contained in GM/TT0126 and GM/TT0129. The Signal Engineer is responsible for the design of: a) All fishplate bonds in non­traction rails. b) All fishplate bonds in traction rails of a.c. only electrified areas. c) The position of all insulated rail joints. d) All jumper bonds between separate sections of non­traction rails.

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e) In a.c. electrified areas (excluding the former Southern Region), all rail to impedance bond connections and connections between impedance bonds on the same track. f) In dual a.c./d.c. and d.c. electrified areas (excluding the former Southern Region), the responsibility for impedance bond connections is subject to special arrangements between the Signal and Electric Traction Engineers. g) On the former Southern Region, impedance bond connections for track circuit only purposes. h) All track circuit rail connections. i) Identifying the need for Yellow Bonding and specifying which bonds are to be yellow.

The Electric Traction Engineer is responsible for the design of: a) All fishplate bonds in d.c. or dual a.c./d.c. traction rails. b) All jumpers bonds between separate sections of traction rails and between the centre connection of impedance bonds in different tracks. c) On the former Southern Region, rail to impedance bond connections for traction purposes. d) All other permanent traction related bonding. 2.4 Adjacent Lines In all cases where lines run adjacent to or cross each other, but are not physically connected, all these lines must be represented on the bonding plans and the bonding plans cross referenced to each other.

3 Track Circuit Nomenclature

Identification of individual track circuits is to be in accordance with Standard Signalling Principle No. 54 and must be shown on plans at convenient intervals within the respective track circuit. To avoid confusion with other plan annotation, the following Track Circuit designations are to be avoided: B, F, I, N, O, R, Q, T, CL, OL, HVI, RB, RN, RR, RT, RX, TB, TC, TF, TFR, TI, TJ, TN, TO, TR, TX, VT, IBJ, IRJ, OCC.

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4 Choice of Track Circuit Type

There are a number of design features of track circuits which constrain choice for a given application: a) The need to detect vehicles on poor rail surfaces. b) The need or otherwise to avoid insulated rail joints. c) The need for immunity to a.c. and/or d.c. traction interference. d) The need to achieve maximum reliability at economic cost. e) The need to track circuit through complex S & C. The Figure D1 summarises the key attributes and limitations of each type of track circuit. CAUTION: Although general precautions and limits that provide compatibility between rolling stock and track circuits, have been included in the Train Detection Handbook Codes of Practice, these are not comprehensive and special conditions may apply to certain routes to permit the operation of rolling stock. Where new types of rolling stock are to be introduced, existing constraints will require reassessment, as to their adequacy.

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Type

Suitable For Lightly Used Lines

IRJs Required

Immunity From

Suitable For S & C

a.c. 50Hz D.C. Medium Voltage A.C. Immune #1 D.C. Diode TI21 HVI #1 #1 #1 Yes Yes No Yes No No Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes No Yes#4 Yes No Yes No Yes

d.c. No No Yes Yes No No No Yes#2 Yes No No Yes Yes Yes Yes Yes

D.C. Low Voltage Plain D.C. Low Voltage A.C. Immune D.C. Medium Voltage Plain D.C. Medium Voltage A.C. Immune/D.C. Tolerant A.C. WR Quick Release A.C. 50Hz Vane A.C. 83.3Hz Vane Reed Aster/SF15

No No No No No

Yes Yes Yes Yes No

No No Yes Yes No

No Yes Yes Yes No

Yes Yes#3 Yes#3 Yes No

Notes: # 1 Preferred track circuits for new works. # 2 Limited dc immunity. Used in an area of ac lines close to ac/dc dual lines not fitted with any means of isolating the traction rail systems. Use must be subject to a proper immunisation evaluation exercise. # 3 Single rail type has restricted length but adequate for S & C application. Double rail type is difficult in complex S & C but permits long length in plain line. # 4 The use of TI21 on ac electrified lines requires the earthing of lineside structures to be to a separate conductor rather than to the rail. This precludes the use of TI21 on ac lines unless part of a major new electrification scheme.

Figure D1

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5 Cut Sections

Designing cut sections into a track circuit is a method of reducing the continuous length. The track circuit is split into individual track circuits, each one controlling the same final TPR. They are indicated as one track circuit on the signalman's panel. Special care must be taken where an individual section of such a track circuit is used separately for control purposes (eg. level crossing timing). The cascading of cut sections (ie. controlling the feed to a track circuit by the relay of the next track circuit) is not permitted. The individual cut sections should be either returned individually to the interlocking or summated in the TPR lineside circuit or, in the case of SSI, summated in the data. Cut sections must be identified in accordance with GK/RT0009 (ie. AA1, AA2, AA3, etc) in the direction of normal running. The two portions of a centre fed jointless track circuit are treated separately for this purpose (eg. AA2 and AA3 in Figure D2).

(50HZ) Track Circuit AA1 AA2

(Centre Fed) Jointless Track Circuit AA3 AB

Relay

Feed

AA2 RX

AA2/3 TX

AA3 RX

AB RX

Figure D2

Where a monitoring device is provided, it must indicate to the technician the location at which the failed relay/receiver is housed, irrespective of the line affected. With reference to Figure D3, an example of the labelling for an individual display would be "Loc 10 (AA2, AA3, BC2, BC3)".

AA2 AA3 RX RX AA2 BC3 BC2 BC3 RX BC2 RX AA3

AA3/4 TX AA4 BC1

AA4 RX

AB1 TR AB1 BB6

BC1/2 TX LOC. 11

BC1 RX

BB6 RX

LOC. 10

LOC. 12

Figure D3

Track circuits must not consist of more than two non­monitored cut sections (where track circuits are centre fed, four receivers (Rxs) may be non­ monitored).

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The monitoring device will usually be housed at the nearest interlocking, but this will largely be governed by the routine and out­of­hours fault finding cover arrangements which exist in the vicinity. The transmission of information to the monitoring device may be achieved by additional FDM channels, a low­cost FDM system approved for use in signalling or telecommunications cables or direct wire circuits.

6 Operating Times

6.1 Time Delays There can be significant differences between the drop­away and pick­up times of different types of track circuit, such that the rear track may register clear before the forward one registers occupied. The detection of the vehicle is therefore momentarily lost, resulting in a wrong side failure, which could permit the irregular release of vital interlocking. To overcome this, additional time delays must be built into the pick­up time of track repeaters, the precise requirement being dependent upon the combination of track circuit types involved. The indication circuits to the signalman may be transmitted via a TDM or FDM link. Therefore the transmission system reaction times must also be considered to ensure that the signalman does not observe an apparent loss of train detection. 6.2 Operating Categories And Conditions In order to simplify the number of possible permutations, track circuits are assigned to operating categories as follows:

Track Relay Operating Characteristics Slow to Pick Up - Quick to Drop Away Medium to Pick Up - Medium to Drop Away Quick to Pick Up - Slow to Drop Away Track Circuit Type TI21 UM71 (French D.C. (all types) Phase sensitive a.c. (50Hz, 75Hz & 83.3Hz) Aster Reed with adjustable track filter Western Region "Quick Release" (a.c./d.c.) Diode Coded GEC Alsthom High Voltage Impulse (HVI) Reed without adjustable track filter

Operating Category A B C Operating Category A A B B B B B B B C C

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With Geographical systems, the differing combinations of abutting categories of track circuits need to be examined and dealt with specially, according to the original design principles. With free wired relay interlocking and SSI, they must be dealt with as follows: Category A When used with a free wired relay interlocking, these track circuits do not require a slow to pick up TPR. Therefore, the TR may be used directly in controls. When used with an SSI, standard track circuit data must be used. Category B When used with a free wired relay interlocking, these track circuits require one slow to pick up TPR, in accordance with Figure D4 When used with an SSI, standard track circuit data must be used. Category C and Category B abutting Category C When used with a free wired relay interlocking, these track circuits must be provided with two slow to pick up TPRs, in accordance with Figure D5. The TR and TPR must be in the same location case or equipment room. The T2PR must be controlled directly by contacts of both TR and TPR to prevent the drop­ away of T2PR from being unnecessarily delayed whilst still achieving the delayed pick­up required. When used with an SSI, track circuit data with "extra delay" must be used. Where the time delay is achieved by relay cascade, it is important that other contacts of the TR and any intermediate repeater relays are not used for control indication purposes. To prevent inadvertent subsequent use, a suitable note must be made on the Contact Analysis Sheet. A schedule must be provided listing all TPRs, the individual sections repeated by each TPR and the type of track circuit (including the frequency in the case of a jointless track circuit).

EG TR B50

BR 933 EG TPR

EG TR N50

Figure D4

EG TR B50 EG T2PR BR 933 EG TPR EG TR N50 EG TPR EG TPR

BR 933

Figure D5

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7 Track Circuit Interrupters

The interrupter (BRS-SM 374) is designed to be mounted on the stock rail, not the switch rail, and is electrically insulated from it. It is to be mounted as near as possible to the switch toe, at a position where the flangeway gap is not less than 70mm when the switch is closed. An interrupter may be either directly controlled in series with the track circuit or part of a separate circuit utilising an interrupter relay according to circumstances. The interrupter must be part of a separate circuit unless all of the following conditions apply:

· · ·

The line is non­electrified. The track circuit on which the interrupter is wired is a d.c. track circuit. The operation of a track circuit by by the interrupter will place to danger any necessary signal on adjoining lines.

Note: The bonding of the interrupter must be of opposite polarity to the rail on which it is mounted. In all other circumstances, the interrupter must be part of a separate circuit incorporating a track circuit interrupter relay. The interrupter relay is controlled directly by the interrupter itself and its front contacts are used to control all repeat relays of the required track circuit. Where necessary, an interrupter relay may control more than one track circuit or may be controlled by more than one interrupter.

8 Length of Track Circuits

Minimum To cater for the longest wheel base vehicles, a standard minimum effective track circuit length of 18.3m must be provided for new and altered works. If this minimum length cannot be achieved, alternative safeguards must be provided, (eg. sequential clearance of the track circuits in the interlockings). Maximum The maximum lengths quoted in individual Codes of Practice within the Track Circuit Handbook are based on a ballast resistance of 3km for timber sleepered track and 5km for concrete sleepered track. If it appears likely that a track circuit will be required to operate at or near its maximum permitted length, tests should be made to ascertain whether ballast conditions etc, are satisfactory, particularly in wet weather, before the scheme design is finalised. The unpredictable effect of level crossings should also be borne in mind. On electrified lines, track circuits may have to be further restricted in length in order to limit the effects of interference from the traction system. Certain track circuit types require a greater minimum length due to their operating characteristics. See the relevant Code of Practice within the Track Circuit Handbook

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9 Track Circuit Gaps and Staggered IRJs

It is essential that all classes of vehicle, irrespective of wheelbase arrangement, are detected by the track circuiting, otherwise false track circuit clearance may lead to premature movements of points or irregular release of signals. Based on the dimensions of existing rolling stock and allowing for future developments, the following shall apply: a) The maximum dead section between two track circuits in areas of continuous track circuiting is 2.6m. This is the minimum wheelbase of vehicles working unattached. b) Opposite IRJs must be regarded as the ideal arrangement. If unavoidable, physically staggered overlaps between nominally opposite IRJs must not exceed the following limits: Non­electrified areas Electrified areas if the traction rails overlap Electrified areas if the insulated rails overlap Isle of Wight lines 2.6m 2.6m 2.1m * 1.7m *

Note*: These distances are stipulated by the Electric Traction Engineer to prevent a motor bogie losing its negative return path (see Figure D12 for clarification). a) There must be at least 18.3m between the nearest joint of any physically staggered pair and an IRJ defining a clearance point at the end of the track circuit. Where this cannot be obtained, special sequential controls must be provided. b) If the physical stagger exceeds 1.6m, there must be at least 18.3m between the nearest joint of the staggered pair and the next IRJ. If the stagger is less than 1.6m, this distance may be reduced to 11m. Where the requirement cannot be met, special sequential controls must be provided. c) Full details of critical dimensions for train detection are contained in GK/RT0011.

10 Selective Operation of Track Circuits

Operation of a portion of a track circuit by the selection of the positions of a set of points is not permitted. Such portions must be separately track circuited.

11 Bad Rail Surface

At locations where oil film or rust is excessive, (eg. traction depots, terminal platform lines, etc), a stainless steel strip can be applied to the surface of the running rail by the Permanent Way Engineer. This must be shown on bonding plans, using the symbol specified in Part C. The vibration caused by the resulting uneven rail surface restricts its application to very low speed applications (5 mph maximum). Alternatively, the GEC Alsthom High Voltage Impulse (HVI) track circuit may be used (see GK/RC0756).

12 Emergency Crossovers

Where a crossover is clipped and padlocked or worked from an adjacent ground frame and subject only to an emergency release, track circuiting is not required for movements over the crossover. RAILTRACK D9

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13 Insulated Rail Joints and Bonding

13.1 Definition of Bonding Types When bonding sections of rail together to form track circuits, equipment of differing performance has to be used depending upon the type of track circuit and the type or absence of electrification; eg. a jumper bond or fishplate bonding may vary in design depending upon:

· · ·

whether or not it is part of a traction rail system; whether or not it is proved intact via series bonding.; whether or not it is part of a non­series "safety­through­diversity" system.

In order to avoid repetition of bonding equipment detail in each section of this handbook, a method of classifying bonding types has been developed in which fishplate bonding is identified separately from jumper bonding, the `family tree' being shown in Figure D6.

Bonding

Jumper Bond(ing)

Fishplate Bond(ing)

Standard Jumper Bond(ing)

Traction Jumper Bond(ing)

Yellow Standard Bond(ing)

Yellow Traction Bond(ing)

Standard Fishplate Bond(ing)

Traction Fishplate Bond(ing)

Figure D6

13.1.1 Fishplate Bonding This type of bonding is used to improve the reliability of the electrical connection between pieces of rail which are already in casual electrical contact by virtue of their construction. Whilst the most obvious item in this category is the un­ insulated fishplate, this method of bonding extends to elements of S & C, such as crossings, wing rails etc, where the components are also bolted together without intervening insulation. Fishplate bonding is not shown on bonding plans. There are two types of this bonding: Standard Fishplate Bonding Used to bond all fishplate rail joints on non­electrified lines and a.c. only electrified lines. On d.c. or dual a.c./d.c. electrified lines, this bonding is only used on the insulated (signal) rail of single rail track circuits. The most common method is two galvanised iron bonds attached to the rail at each end with driven taper pins. It is installed by the Signal Engineer in all cases. Traction Fishplate Bonding Used to bond all fishplate rail joints on d.c. or dual a.c./d.c. electrified lines which form part of the traction current system. It is the responsibility of the Electric Traction Engineer. 13.1.2 Jumper Bonding This covers jumper cables which bond together sections of rail for track circuit and/or traction purposes; those sections may themselves be formed from many D10 RAILTRACK

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individual pieces of rail which are bonded together with fishplate bonding. There are four types of jumper bonding: Standard Jumper Bonding A jumper bond between sections of rail which is proved intact as part of fail­safe series bonding and does not form any part of a traction current system. It is a light current cable installed by the Signal Engineer. Yellow Standard Bonding Used on non­electrified lines or long spurs of insulated (signal) rail on electrified lines. A jumper bond between sections of rail which is not proved intact by fail­safe series bonding. Safety is assured by installing at least three alternative jumpers, such that two jumper disconnections are not, by themselves, unsafe. It is a mechanically robust light current cable installed by the Signal Engineer and identified either by a yellow sheath or a yellow sleeve at its termination. Its mechanical strength allows its electrical integrity to be inferred from regular visual inspection. Traction Jumper Bonding Traction rated bonding attached to the traction rail of electrified lines but which is not relied upon for the integrity of track circuit operation. Yellow Traction Bonding Provided in accordance with the same design principles as Yellow Standard Bonding, except that it is traction current rated. It is installed by the Electric Traction Engineer (except impedance bond end connections which are connected by the Signal Engineer). 13.2 Design Principles for Yellow Bonding The design principles whereby the need for yellow bonding is identified are the same for both non­electrified and electrified lines. Electrification only affects the rating of bond to be installed and the organisation responsible for its installation and subsequent maintenance. Yellow bonding shall ensure that a single or double disconnection will not result in an unsafe condition. See GK/RT 0252. 13.2.1 Yellow Bonding Where separate sections of rail are required to be electrically interconnected in parallel, each section is to be bonded to the adjacent section at each point of abutment using a yellow bond. Each spur extremity is to be bonded to another part of the same electrically common network, which is not itself a part of the same spur, using a yellow bond. In addition to any switch reinforcement yellow bond, each section must have at least three yellow bonds attached to it in different physical locations, which should be a minimum of 20m apart. Additional yellow bonds are to be installed to achieve this and, wherever possible, the additional bonds must connect to a different section from those already fitted. In the case of non­electrified multiple track plain line, the common rails of parallel tracks must be cross bonded together using yellow bonds at the site of feed/relay ends and at least 1km intervals. Yellow bonds are to be clearly identified on bonding plans as shown in Part C. RAILTRACK D11

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Examples of the application of this principle are shown in Figure D7.

Other Yellow Bonds Y Y Y

Switch Reinforcement Yellow Bond Y

Figure D7 13.2.2 Switch Reinforcement Yellow Bonding Wherever the rail designated to require yellow bonding passes through a set of point switches, its continuity is to be strengthened by a "Yellow Bond" as shown in Figure D8. Installation for traction rails is the responsibility of the Electric Traction Engineer, and for non­traction rails is that of the the Signal Engineer.

Common Rail Through Points Y

OR

Y

Figure D8

13.3 Bonding Configurations In order to avoid repetition whilst clearly identifying requirements, it is useful to define the four bonding configurations and associated bonding standards which can be used for particular cases: 13.3.1 DRDS (Double Rail/Double Series) This is where each track circuit is fully isolated from its neighbours by IRJs in both rails or tuned zones and each rail of the track circuit is series bonded D12 RAILTRACK

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throughout except for permissible spurs (see 13.4). In electrified areas, there are no other electrification related bonds from either rail other than via the centre connection of impedance bonds. Non­electrified Lines Electrified Lines Standard jumper bonds to both running rails. Traction jumper bonds to both running rails.

13.3.2 DRSS (Double Rail/Single Series) This is where each track circuit is fully isolated from its neighbours by IRJs in both rails, and one rail of the track circuit is series bonded throughout except for permissible spurs (see 13.4). The other rail of the track circuit contains elements of parallel bonding. Non­electrified Lines Standard jumper bonds to the series bonded rail and to the true series bonded elements of the other rail. Yellow standard bonds to interconnect the parallel elements. Electrified Lines Not applicable

13.3.3 CR Class (Common Rail) This is where each track circuit is isolated from its neighbours by IRJs in one rail only (the signal rail), and that rail is series bonded except for permissible spurs (see 13.4). The other rail is electrically common with adjacent track circuits and may have parallel bonded elements, but does not carry traction current. Non-electrified Lines bonded Standard jumper bonds to the series Signal Rail. Yellow standard bonds to the common rail. Electrified Lines - Not Applicable 13.3.4 SR (Single Rail) This is where each track circuit is isolated from its neighbours by IRJs in one rail only (the signal rail), and that rail is series bonded except for permissible spurs (see 13.4). The other rail is electrically common with adjacent track circuits and forms part of a mesh carrying traction current. Non­electrified Lines Electrified Lines Not applicable Standard jumper bonds to the signal rail.

Yellow traction bonds to the traction rail. 13.4 Permissible Spurs This clause covers the permissible arrangements for parallel bonded spur sections of an otherwise series bonded track circuit section. Parallel bonded spurs on common/traction rail sections are not separately identified, since they are covered by the general requirements for bonding of such rails. Spurs up to 13m, measured from the first joint or weld of a crossing, shall be permitted as shown in Figure D9. provided that there is a maximum of one fishplated joint between the series bonded rail and the end of the spur, and that this joint is properly bonded. Spurs up to a maximum of 60m, measured from the first joint or weld of a crossing, shall be permitted, provided they are yellow bonded to the parent series rail.

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Only One Bonded Fishplate Joint Permitted

13 ME E TR

A SM

X.

Y

X

If X Or Y >13m Then Additional Cross Bonds To The Stock Rails Will Be Required

Figure D9

13.5 Series Bonding Simplification If series bonding becomes complex, it imposes penalties on both reliability and maintenance. The option of cut sections should then be considered. A maximum of four point ends or fifteen IRJs (including boundary joints) per track circuit is strongly recommended. 13.6 Applications of Bonding Configurations

Type of Track Plain Line S&C Complex S&C Figure D10

Non­electrified Lines DRDS or CR DRSS * CR #

A.C. Electrified Lines DRDS or SR SR SR

D.C. Electrified Lines DRDS or SR SR SR

Notes: * # Where DRDS is impracticable. Where DRDS and DRSS are impracticable. Maximum permitted length is 200m.

13.7 IRJs Between Differing Track Circuit Types IRJs must be provided in both running rails at the point where differing track circuit types abut. Special cases will be discussed in the relevant sections. 13.8 IRJs at Signals Where a signal is replaced to danger by occupation of the first track circuit ahead, the IRJs will generally be positioned between 5m - 20m beyond the signal. For further information see SSP 62. 13.9 Jointed Track Circuits Abutting Non­track Circuited Line In order to detect defective IRJs where a jointed track circuit adjoins a non­track circuited section, a short circuit bond must be provided immediately beyond the IRJs, as shown in Figure D11. This bond shall be a standard bond on non­ electrified lines, or a traction standard bond on electrified lines.

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AA

Figure D11

13.10 IRJs at Electrified/Non­electrified Boundary 13.10.1 Running Lines At the boundary between electrified and non­electrified lines, initial isolation IRJs must be provided in both running rails at a sufficient distance beyond the end of the catenary/conductor rail to prevent an overrunning train from injecting traction current into the rails on the non­electrified side of the joints. The collector shoes on d.c. multiple units are interconnected within each multiple unit set. Therefore, it is the length of the longest multiple unit which will dictate the position of the initial isolation IRJs in d.c. traction areas. All track circuits within 800m of the initial isolation IRJs on the non­electrified side must be immune to the traction system and provided with double rail IRJs. Where there are no track circuits on the non­electrified side of the initial isolation IRJs, a second set of isolation IRJs must be provided in each rail 800m beyond the initial isolation IRJs. If any siding occurs within the above 800m areas, a second set of isolation IRJs must be provided in each rail of the siding immediately clear of the running line. 13.10.2 Sidings Off Electrified Lines In electrified traction areas, two sets of IRJs are to be provided in both rails at least 27m apart. These are to be provided beyond the last track circuit in private sidings leading to stores or depots containing flammable or explosive substances, and in other sidings where isolation from electric traction is required. In d.c. electrified areas, the traction return bonding must be extended by the Electric Traction Engineer onto track circuited non­electrified lines and sidings for at least 120m beyond the conductor rail or the tips of the points. Track circuits beyond this distance must be fully isolated with double rail IRJ's or the traction return bonding must be continued for at least another 335m. This ensures that an electric traction unit inadvertently entering a non­electrified area will not lose its negative return whilst any shoe is still in contact with a conductor rail. On lines where Eurostar operations are authorised, the above distances will need to be extended accordingly. If the line concerned connects with a d.c. electrified line at more than one point, it must have continuous traction bonding throughout in order to prevent traction return current passing through the couplings of a train which is bridging two traction portions of a siding. 13.11 A.C. and D.C. Electric Traction Areas Abutting Where there is a requirement for inter­running with trains operating on differing electrification systems, IRJ separation between the differing traction systems cannot generally be achieved. In these areas, a suitable "buffer" zone of dual immunisation must be provided. As a general guide, for track circuit applications, immunisation against 50Hz electrification should be maintained for a distance of 3km beyond the extremity D15

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of the 50Hz system. Immunisation of track circuits on the a.c. electrified system and non-electrified lines against d.c. interference, will usually involve significantly greater distances (up to 20 km). The extent of such a zone is dependent upon track layout, position of feeder stations and traction load etc, and requires specialist assessment and subsequent verification. 13.12 Buffer Stops Rail mounted buffer stops in double rail track circuited areas must be fully insulated. In the case of single rail track circuits in a.c. electrified territory, they should be insulated from the signal rail. The type of IRJ provided close to buffer stops must be of a design which offers similar tensile strength to conventional steel fishplates (see GK/RT0031). 13.13 Electrical Stagger Where the electrical energy of one track circuit is capable of operating the adjacent track circuit due to IRJ failure, the polarity (d.c.) or phase (a.c.) of each must be arranged so that they oppose rather than reinforce each other. The intent being that IRJ failure will not result in false operation. The following methods are available to counteract lack of proper electrical stagger:

· · · ·

Provide an additional transposition to restore correct electrical stagger. Abut feed ends. Provide a feed end relay (d.c. track circuits only). Convert one track circuit to a non­interfering form of energy.

13.14 Fouling and Clearance Points Where tracks cross or diverge etc, it is necessary to define track circuit limit dimensions which ensure that traffic passing along one route is not obstructed by vehicles standing on the other. The two critical dimensions are referred to as the fouling point and the clearance point, as shown in Figure D12.

1970mm (Between Running Edges)

4880 MM Crossing Nose Fouling Point Clearance Point

Figure D12

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13.14.1 Fouling Point This is a position a short distance away from the point of running line divergence (crossing nose). Should any part of a vehicle on one track be between the crossing nose and the fouling point, it will make physical contact with any vehicles passing on the other route. Where the angle of divergence is less than 45°, the fouling point occurs where the distance between the running edges of the two rails is 1970mm, measured at right angles from the track for which the fouling point is being determined. Where the angle of divergence is greater than 45°, the fouling point occurs at 1970mm from the crossing nose, measured along the track for which the clearance point is being determined. In the case where tracks become parallel with a running edge separation of less than 1970mm, the fouling point occurs where the tracks first become parallel. 13.14.2 Clearance Point As track circuits detect the wheelsets of vehicles which are inboard of bodyshell limits, the boundary of any track circuit designed to give assurance of clear passage along the other route must be some distance beyond the actual fouling point. This is defined as the clearance point. In the absence of protecting trap points, the clearance point is 4880mm further from the crossing nose than the fouling point. Where trap points are provided, the clearance point is defined as the switch tips of the trap points. In both cases, the IRJ defining the track circuit limit is positioned at the first suitable rail joint beyond the clearance point. All clearance points shall be shown on the bonding plans. 13.14.3 Minimum Length of Track Circuits To prevent a vehicle bridging a short track circuit and consequently providing a false clear condition, the minimum length of a track circuit is 18.3m. 13.14.4 Staggered IRJs Where practical, IRJs should be positioned in each rail so that they are opposite to each other. Where a physical stagger between opposite IRJs is unavoidable, the maximum physical stagger must not exceed 2.6m. This is the minimum wheelbase of vehicles which can work unattached. To ensure that motor bogies do not become insulated from the traction return path, the physical stagger for a signal rail overlap in electric traction areas must not exceed 2.1m. On the Isle of Wight, vehicles used have smaller bogies and as such, the maximum physical stagger is reduced to 1.7m. In order to avoid loss of detection of a single car, four wheel vehicle, the permitted distance between inner joints of staggered pairs of IRJs must not be less than 11m, where the IRJs are staggered at a distance of less than 1.6m (the minimum bogie wheelbase). If however, either pair of IRJs are staggered at a distance greater than 1.6m, or provide a clearance point (see Clause 13.14.2), then the distance between inner joints of staggered pairs must be not less than the 18.3m minimum track circuit length. Note: When consulting other documents, care should be taken to ascertain whether "running edges" or "outside edges" of rails are being referred to.

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Figure D13 gives examples of the application criteria for IRJs, the references being as follows: 13.15 RJ Summary Notes on Figure D13: C D E F L S Clearance for vehicle overhang. Distance between inner joints of staggered pairs. Distance between staggered pair and end of track circuit. Fouling point. Minimum effective length of track circuit. Physical Stagger Not less than 4880mm from the fouling point to the IRJ. Not less than 11m if both of pairs staggered < 1.6m. Otherwise, not less than 18.3m. 18.3m minimum. 1970mm between running edges 18.3m minimum 1.7m max: Isle of Wight lines only. 2.1m max: Signal rail overlap on electrified lines. 2.6 max: Other cases.

Figure D13

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13.16 Permanent Way Engineering Considerations The following should be considered relative to IRJ provision in S & C as constrained by permanent way engineering considerations:

· · ·

IRJs adjacent to cast crossings should be avoided wherever possible. IRJs run over in the high speed route should be avoided as far as possible. There should be a minimum distance of 200mm between chair or rail fastenings of opposite polarity/phase to reduce the probability of failures due to metallic litter, etc.

14 Track Circuit Equipment Positioning

With a view to obtaining the best possible performance, track circuit equipment should be positioned as close as practicably possible to the associated rail connections, and any maximum limits laid down in the individual track circuit sections must not be exceeded. This also permits better communication between technicians when working apart, undertaking drop shunt tests, etc. In tunnels and on viaducts, the feed and relay ends of a track circuit should be mounted in the same lineside apparatus housing, provided that no electrical parameters are infringed. If the design of track circuit is such that staff are not required to make adjustments (eg. HVI track circuits), the relay or receiver equipment may be grouped in equipment buildings provided that no electrical parameters are thereby infringed. Disconnection boxes may be provided if site conditions warrant. These must be shown on wiring diagrams, but are not required on bonding plans unless they contain fuses or arresters.

15 Layout and Wiring of Lineside Apparatus Housing Equipment

All relays should be mounted as near to the top of the lineside apparatus housing as possible. Tail cables are to be terminated at the bottom of the lineside apparatus housing in one of the following manners, as appropriate:

· · · ·

Directly onto the track fuse and link. Directly onto the track fuses. Directly onto two links. Directly onto a surge arrestor.

In d.c. traction areas where the lineside apparatus housing is remote from the track connections, the surge arrester (where provided) and track fuse must be located at the tail cable terminations nearest to the rail connections. Where special restrictions apply to wiring and/or positioning of equipment, this must be clearly shown on all wiring/layout drawings, so that if any alterations are made at a later date, the restrictions are readily apparent

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16 Duplicate Rail Connections

Duplicate connections to the rails are the preferred arrangement for all track circuits, except those which operate at audio frequencies (see the relevant sections for further information). Where duplicate connections are used the method of wiring is as shown in Part E.

17 Communications

It is desirable that communication circuits are available between the feed/transmitter and relay/receiver sites to facilitate setting up and fault finding.The communication circuits may be run in the same multicore cables as the feed, transmitter, relay or receiver circuits. At certain SSI installations, the data cables carry communication cores which may be used for this purpose.

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Part E Components and Installation

1 Introduction

This part explains the general components applicable to all track circuits. Components specific to a particular type of track circuit are listed in the relevant Approved Code of Practice within this handbook. Installation procedures for individual track circuit types are detailed in the relevant Approved Code of Practice within this handbook. Note: The Catalogue Numbers shown within this document are not directly controlled by Railtrack and as such, will not be maintained and kept up to date. Although every effort has been made to ensure that these were correct at the time of publication, it is therefore recommended that your supplier is contacted and a check is made with regard to the accuracy of these catalogue numbers prior to use.

2 Responsibilities for Bonding Installation

The Signal Engineer is responsible for: a) All fishplate bonds in non­traction return rails. b) All fishplate bonds in traction return rails of a.c. only electrified areas. c) The position of all IRJs. d) All jumper bonds between separate sections of non­traction rails. e) In a.c. electrified areas (excluding the former Southern Region), all rail to impedance bond connections and connections between impedance bonds on the same track. f) In dual and d.c. electrified areas (excluding the former Southern Region), the responsibility for impedance bond connections is subject to special arrangements between the Signal and Electric Traction Engineers. g) All track circuit rail connections. h) The insulation of all rods connected to the rails and switches (eg. detection, facing point lock, point main drive and supplementary drives). The Electric Traction Engineer is responsible for: a) All rail joint bonds in d.c. or dual a.c./d.c. traction return rails. b) All jumper bonds between separate sections of traction return rails and between the centre connection of impedance bonds in different tracks. c) On the former Southern Region, rail to impedance bond connections for traction purposes. d) All other permanent traction related bonding. The Permanent Way Engineer is responsible for: a) The insulation of all point soleplates, tiebars and stretcher bars. b) The installation of all IRJs. The requirements and responsibilities for the installation of bonding on electrified lines are laid down in GM/TT0126 and GM/TT0129. RAILTRACK E1

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3 Track Circuit Interrupters

The standard insulated track circuit interrupter assembly is shown on drawing BRS-SM 374, an extract of which is shown in Figure B11. Catalogue numbers are as follows: Description Assembly complete to BRS-SM 374 Taper pin, BRS-SM 411, 60mm Body unit to BRS-SM 375 Insulations to BRS-SM 376 Item 1 Item 2 Item 3 Insulating bush Insulating washer Channel insulation Catalogue No. 86/44001 86/44011 86/44003 55/27570 55/25976 55/28981 55/27201

: : : : : : :

The interrupter is mounted on the stock rail, not the switch rail, by means of an M20 insulated bolt passing through a 28mm hole in the rail web. A second 28mm hole, 130mm from the first, may be provided to enable the wiring to be brought out towards the sleeper ends. The interrupter is positioned as near as possible to the switch toe, commensurate with maintaining a flangeway gap of not less than 70mm with the switch closed. Figure E1 gives the nominal positioning. The temporary repair of track circuit interrupters by means of wrapping the cable around the stock rail is forbidden. Refer also to Part D.

A POSITION OF INTERRUPTER

Rail Type 95 lb.Bullhead

Switch Type A B C D A B C D E A B C D E

Dimension 'A'(mm) 4180 4780 5900 7620 4180 4955 6675 7635 10185 4705 6125 6835 8255 11095

113 lb. Inclined

113 lb. Vertical

Figure E1 E2 RAILTRACK

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4 Identification of Track Circuit Boundaries

Where required, a plate may be fixed to the sleepers or to the lineside track circuit equipment to assist identification of track circuit limits. Wherever a track circuit boundary occurs in a tunnel, a plate bearing the track circuit name or number must be fixed to the tunnel wall on each side of the IRJ (or equivalent in the case of a jointless track circuit).

5 Protection of Cross Track Cables

5.1 General Cross track tail cables and jumpers should be protected from damage, eg. by means of orange plastic pipe. This protection need not be continuous across the cess or six­foot, but should be used where tail cables pass under walkways. 5.2 Orange Pipe Installation Cut the pipes to length so that the ends are clear of the ballast shoulder. This helps to prevent ballast from entering. Restrict each pipe length to 3 metres maximum as long lengths of pipe will not move out of the way if struck by a tamper tine. However, in S & C areas it may be necessary to use longer lengths to give full protection across the sleeper bay. It is particularly important that the pipe is laid straight and centrally in the sleeper bay, and that holes for rail leads are as close to the rail as possible, in order to give maximum protection from tamping machines. Do not use the ballast to restrain sideways movement. Dig the pipe into a shallow depression in the ballast keep it visible but allow sideways movement if struck. Do not fill a pipe more than half full with cables. This reduces the chance of cable damage if the pipe is crushed by a tamper. If more cables have to be run, provide another pipe. Wherever possible, do not install a pipe in a sleeper bay adjacent to conductor rail ramped end to prevent the pipe being ignited by sparks from the collector shoe. To allow the Permanent Way Engineer maximum opportunity for tamping, do not position a pipe:

· · ·

in a bay where there is a rail joint or weld, or in a bay adjacent to them; in a bay which is less than 0.37 metres (1 foot 3 inches) wide, unless there is no other choice; in a bay which already has an orange pipe or other obstruction, or in one adjacent to it. Always leave at least one clear bay between obstructed bays.

If a pipe needs side holes for the exit of track connection cables: a) Cut the holes with a good quality 40 to 50 mm fixed diameter hole saw. Do not use other methods of making holes. Round off the sharp edges of the hole with a file or deburring tool.

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b) Clip the pipe to the foot of the outside of flat bottom rail. On bull-head rail a cab-lock round the pipe may be secured to the rail web with a taper pin. These fixings prevent the pipe rotating or moving along its length and cutting into the cable. The clip will still permit some sideways movement if the pipe is struck. c) Leave sufficient slack in the cable so that if the pipe does become detached from the rail, the connection will not be pulled away. However, excessive amounts of slack cable should be avoided in order to minimise the likelihood of vandalism. Orange pipe must not be cut along its length unless special dispensation has been given. Orange pipe must not be used in tunnels or other areas of restricted Ventilation. If the pipe does ignite, it is difficult to extinguish and gives off heavy fumes. Orange pipe is generally suitable as protection for crossing walkways if it is let into the surface. When tail cables need to be protected for other reasons, such as chemical spillage in sidings or for staff safety, a concrete route or under track buried crossing should be used. Catalogue numbers are given in clause E11.

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Figure E2 shows the general arrangement for orange pipe installation.

Rail web

pipe clip

Orange pipe

Cable strap (use as few as possible) Leave some slack here to allow for minor slews. No rail web pipe clip

Orange pipe

Dis Box

No rail web pipe clip

Cable route

Note

Dis Boxes should be mounted in a permanent Green Zone as defined in GO/RT3073.

Figure E2

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6 Mechanised Track Maintenance

All equipment on the track must be installed clear of the tamping zones indicated in Figure E3, except cross track orange pipe. All sleepers may be tamped, except those on either side of Silec treadles and point rodding.

290 405 Tamping Zone

405 290

Figure E3

7 Rail Drilling

For conventional grades of rail steel, Signal Engineers use rail drilling machines. They are preset to drill the two holes required accurately with no adjustment necessary. Available drilling machines and attachments, together with the Catalogue Numbers, are listed below: Description Rail bond drilling machine, hand operated (single spindle) Rail bond drilling machine, 110V/500W (twin spindle) Rail bond drilling machine, petrol engine (twin spindle) S & C drilling attachment, for use with 39/41823 Flexible drive, 8 feet long, for use with 39/41823 Notes: * The drilling machine fits over the rail and cannot be left in position whilst trains pass. The drilling machine clamps to the underside of the rail and can be left in position whilst trains pass. : : : : : Catalogue No. 39/41822 * 86/43690 # 39/41823 * 39/200000 39/54510

#

At sites of heavy wear, particularly in S & C, The Permanent Way Engineer may fit specially hardened steel rails which can only be drilled with special drill bits. Whilst the Permanent Way Engineer permits drilling of 7.2mm holes for taper pins by Signal Engineers, drilling of larger holes in hardened steel is a specialist job to be undertaken by Permanent Way Engineering staff.

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The following table of Permanent Way Engineer's rail markings is included to assist staff in the identification of rail types. The brand marks appear as raised characters on the rail web; confirmation is also provided by paint marks on new rail and (in some cases) by its magnetic properties.

Type Normal Wear resisting A Wear resisting B BSC 90 90kg chrome 100kg chrome AMS HC AMS LC MHT Remarks: 1: 2: 3: Figure E4

Brand Mark None A B AA 1CR 1CR Manganese Manganese W -

Paint Marks None 2 blue 3 blue 1 blue/1 white 1 red 2 red 1 green 1 green -

Magnetic Remarks Yes Yes Yes Yes Yes Yes No No Yes 1 1 1 1 1 1 2 2 1&3

Can be drilled using conventional methods. Can be drilled only with special tools/techniques. Identification not yet agreed.

8 Rail Connections

8.1 Introduction The various methods of making electrical connections to the rail are explained below: 8.2 Taper Pins The taper pin requires a 7.2mm hole, 57±2mm above the base of the rail, to be drilled through the rail. The taper pin consists of a threaded section to which the various connectors are attached, and a non­threaded end which is tapered to ensure that the pin is firmly fixed to the rail. Fit the taper pins into the holes and hit the non­threaded ends with a hammer to ensure that the pins and the rail are in electrical contact. Catalogue numbers are as follows: Description Track circuit maintenance kit Comprising: Pin, taper, BRS-SM 411, 55mm long Nut, self locking, stainless steel,M6 Washer, stainless steel, M6 (20) Nut, stainless steel, M6 (10) (10) (10) : : : : : Catalogue No. 88/10037 86/44013 3/179995 3/190825 3/175013

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8.3 Pin Brazing Pin brazing is a method of connecting threaded pins to the rail using electric­arc brazing. This method will usually be used at new sites or where re­railing takes place and may be used on standard and hardened steel rails. Pin­brazed studs will be installed by Signal or Permanent Way Engineering staff; any person engaged in these operations must hold a Certificate of Competency for the task to be undertaken. An M12 pin brazed stud may be brazed to the rail web, as shown in Figure E5. The minimum spacing between connectors is 85mm. The correct torque for attachment of the rail lug to the M12 studs is 60Nm.

200 115

240

57

NOTE Self Locking Nut (Supplied) to be tightened to a torque of 60Nm

Pin Brazed TEE Connector

Figure E5 The threaded pins are brazed to the rail, at a position 57±2mm above the base of the rail, with a silver based filler metal, using a hand held brazing gun operated by either of the following pieces of equipment: Description Portable machine, battery driven on single rail trolley, suitable for track maintenance, which will braze approx. 50 pins to the rail. Large machine, battery driven on double rail trolley. The batteries are recharged by an integral petrol driven generator. This unit has a capacity for 50 brazes per hour and is suitable for new works. Catalogue No.

:

20/3003

:

20/3001

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Both of the above machines require the batteries and the brazing gun to be ordered separately. These are listed along with other spares and attachments as follows: Description VF 2300 Brazing gun VF 2300 Angled gun VF 2300 Extended gun VF 2300KA Brazing gun VFRG Batteries VFLC Batteries VFKA Batteries VFKA 250 Battery unit VFKA 250 Attache case Battery charger for vehicle Battery charger for depot 8mm Ceramic ferrule 9.5mm Ceramic ferrule 8mm Brazing pin 9.5mm Brazing pin Spark shield Contact arm 12mm/M8 Pin holder Contact set complete Contact nipple and disc Ejector rod complete Key set Screw set Rail bond 25mm x 500mm long Rail bond 25mm x 145mm long Rail Bond 25mm x 1500mm long T connector M12 Track end connector V Connector 2 x 25mm x 90mm long : : : : : : : : : : : : : : : : : : : : : : : : : : : : : Catalogue No. 40/515 20/3021 20/3011 20/3010 20/3002 20/3004 20/3007 20/3005 20/3006 20/3008 20/3009 55/27287 55/16001 55/27706 55/41011 40/543 40/507 40/561 40/521 40/555 40/536 40/520 40/556 88/23906 88/23907 86/43511 55/9366 20/3013 46/2183

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8.4 Cembre Cembre is a method by which a copper bush is expanded inside a 22mm hole drilled into the rail web. A bolt is then passed through the copper bush and is used to fix a cable lug to the rail. The copper bush should be inserted and expanded a soon as the hole has been drilled. If this is not possible, the hole should be given a protective coating of jointing paste at the time of drilling and thoroughly cleaned, in the same manner a described for pin drive fittings when the bush is fitted. Refer to clause 8.6 Cembre Parts Rail lead installation kit (M12 steel screw with hollow hex. head, flat steel washer & self locking nut) Copper bush for 22mm dia. hole Expansion plunger. Calibrated high tensile steel Hydraulic tool with hand pump c/w carrying case Go/No Go gauge for checking 22mm rail hole : : : : : Catalogue No. 86/017025 86/017026 86/017027 86/017028 86/017029

To ensure that the drilled hole is the correct size a gauge is used as detailed below and shown in Figure E6 : a) Insert the Go/No Go gauge into the hole. b) The hole may be used only if the green part passes through and the red part does not. c) If the red part passes through, redrill a hole in a different position. d) The inside of existing holes should be thoroughly cleaned and bright.

Green (No GO Column) 22 Dia Red (No GO Column)

GO / No GO Column

57

Figure E6

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Once the drilled hole has passed the gauging test the following procedure is used to expand the copper bush : Refer to Figure E7. a) Insert the copper bush (Item A) into the rail web. b) Insert the calibrated plunger (Item B) on bush flange side, ensuring threaded end projects through to the other side. c) Depress the tool pressure discharge lever (Item C) to ensure the piston is fully retracted. d) Insert the calibrated plunger (Item B) into threaded housing of either tool seating (Item D) by using gauge (Item E) located on hexagon end of item B. e) Pump until the calibrated plunger is completely through.

Running Edge

D

A

B

E

C

D

Figure E7

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With reference to Figure E8, the general assembly procedure of the connector is as follows: a) Insert the hollow hexagonal headed stud into the copper bush so that the thread projects from the bush flange side (this will usually be into the four foot). b) The stud head will surround the projecting part of the bush without touching it. Locate lug onto the stud, add washer and lock nut, then tighten to 60Nm torque.

Running Edge

Type AR 60-3 Steel Stud With Hollow Hex Head (M12)

M12 Washer Self Locking Nut

Cable Lug

Figure E8 Figure E9 shows a typical bonding arrangement.

240 These dimensions are only typical. Refer to Layout Drawing for individual situations.

76

57

NOTE; Self locking Nut (supplied)to be Tightened to a torque of 60 Nm.

Figure E9

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8.5 Aluminio­thermic Welding Thermic welding is a method of fixing threaded pins to the rail by means of a thermo­chemical reaction. It can be used for traction bonding in both a.c. and d.c. traction areas. Two types of studs are available: Description

1

Catalogue No.

/2" x 7/8" fully threaded stud, complete with

nut and washers. 5 /8" stud with nut, spring washer and flat washer.

: :

Available from ERICO. 46/19800.

Note (1): Aluminio­thermic welding is also referred to as Cadweld and Thermoweld. Note (2): Any person engaged in these operations must hold a Certificate of Competency for the task to be undertaken. 8.6 Pin Drive This method should be used only where pin braze or Cembre fittings cannot be used. A bimetal rail lug (Railway Catalogue No. 55/27614) provides an aluminium barrel for crimping to aluminium cable and a copper lug for insertion into the rail. Where pin­drive lugs are used to make connections to the running rails, the 22mm holes are drilled by Permanent Way Engineering staff. If the rail connection is not made at the time of drilling, the hole is immediately given a coating of jointing paste (Railway Catalogue No. 7/026200) to minimise the risk of a high resistance connection due to corrosion. The connection is made as follows: Before the lug is inserted in the rail, it is cleaned of all existing jointing paste and all contact surfaces should be clean, bright, brushed with a circular wire brush (Railway Catalogue No. 5/4266) and re­coated with a uniform layer of jointing paste (Railway Catalogue No. 7/026200). The lug is secured to the rail by means of the rail lug bond pin, refer to Figure E10. Pin size No.1 (Railway Catalogue No. 55/27860) , is driven in with a hammer and is used for the first installation. Pin size No. 2 (Railway Catalogue No. 55/27862) is used for subsequent installations of a lug. Pin size No.3 (Railway Catalogue No. 55/27863) should be used only when the rail hole is oversize, eg. 7/8" rather than 22mm. After installation, surplus jointing paste should be wiped off. All rail lug connections should be inspected after installation to ensure that the lug is tight and free from cracks. Any cracked or loose connections are to be remade.

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41 28 2 x 45O

`X' 0.13

6R

Bond Pin Number Stamped Here Height 6

Figure E10 shows the rail lug bond pin.

Material : Steel to BS 970 Part 1. 070 M20

No

1 2 3

Bond Pin Diameter Catalogue No

14.5 15.35 16.15 86/044010 86/044009 86/044015

Figure E10 8.7 The Preformed Moulded Rubber Connector The rail should have previously been fitted with two threaded studs by one of the methods described in 8.2 to 8.4. Secure the moulded connector onto the threaded studs using the self locking nuts and washers, tightened to a torque of 13 Nm, as shown in Figure E11. Ensure that the stud protrudes at least one full turn through the nut. Do not fit a nut or washer between the rail and moulded connector. Fit the flange clip over the cable and push the clip onto the foot of the rail. Catalogue numbers are as follows: Description Flange Clip, 6.5mm BRS­SM 849 Moulded Flexible TC Lead 2.5mm² 3.0 metres 4.5 metres 6.5 metres 8.0 metres 30.0 metres Catalogue No. 86/43489 86/44022 86/44023 86/44024 86/44025 86/44026

(1) : : : : :

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Cable Termination Label

76mm

TCABR

B (1 )

57 + 2mm

Flange Clip

Taper Pin

Stainless Steel Washer Stainless Steel Locking Nut

Figure E11 8.8 The "L" Plate Connector "L" Plate connectors are used only where preformed cables are inappropriate. The rail is drilled in accordance with Figure E12. Description Track circuit rail connection kit Comprising: Pin, taper, BRS-SM 411, 55mm long Nut, self locking, stainless steel, M6 Washer, stainless steel, M6 Nut, stainless steel, M6 Plate, BRS-SM 848 Terminal, crimped, black sleeve, M6 Flange clip, 6.5mm, BRS­SM 849 Tube, heat shrinkable, 55mm long Catalogue No. 86/44019 86/44013 03/179995 03/190825 03/175013 86/43488 54/119568 86/43489 55/120989

: (2) (2) (4) (2) (1) (1) (1) (1) : : : : : : : :

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Flange clips may also be obtained for larger cable sizes: Description Flange clip, 15mm, BRS­SM 849 Aster and TI21 Track Circuits Flange clip, 23mm, BRS­SM 849 Inductive Loop Reed Track Circuits Catalogue No. 86/43498 86/43499

(2) (3)

: :

Cable Termination Label 76mm

Two Holes 7.2 Dia.

TCABR

B (1 )

57 + 2mm

`L' Plate

Heat Shrink Sleeve

Stainless Steel Washer & Nut Flange Clip Stainless Steel Washer & Locking Nut

Figure E12 The rail should have previously been fitted with two threaded studs by one of the methods described in 8.2 to 8.4. Fit a washer and nut to each threaded stud and tighten to a torque of 13 Nm. Strip back 20mm of the outer sheath of the 2.5mm²(f) cable, followed by 8 - 9mm of the inner sheath to expose the conductor. Slide the crimp terminal onto the cable and crimp it. Ensure that the crimping tool is the correct size, and matches the crimp terminal being used. The kit currently contains an AMP PIDG 6mm terminal, for which a yellow/black handled AMP tool (59239-4) must be used. Slide the heat­shrink sleeve onto the "L" plate and thread the cable through the sleeve until the eye of the crimp is over the end hole of the ``L'' plate.

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Move the heat­shrink sleeve until the entire stripped length of the cable is covered by the sleeve without restricting the securing hole. Apply heat to the heat­shrink sleeve. Before heating, the sleeve is 55mm long, and reduces to about 50mm when it is fully heat­shrunk onto the cable and the plate. Place the "L" plate assembly onto the threaded studs and secure using the remaining washers and the self locking nuts, tightened to a torque of 13 Nm. Fit the flange clip over the cable and push the clip onto the rail.

9 Track Circuit Disconnection Box

The typical arrangement of the track circuit disconnection box is shown in Figure E13. It is mounted on a stake using two M8 studs (supplied with the box) and comprises a moulded rubber back with a slide­on metal cover which can be padlocked using the standard RKB221 padlock. Provision is made to securely clamp both the lineside apparatus housing tail cables and track lead cables in the base of the box. A longer stake is available for use where ground conditions are poor. Description Stake (Angle), 760mm long, to BRS-SM 104/13 Stake (Angle), 1070mm long to BRS-SM 104/11 Track Circuit Disconnection Box : : : Catalogue No. 86/10751 86/88250 86/43877

The termination for each track circuit comprises a four way 2BA link block. The various cables should be terminated as shown in Figure E14 (this enables the individual track leads of duplicated arrangements to be disconnected/tested separately). Note 1: Only one track circuit is allowed in a Disconnection Box and hence double track circuit boxes are not to be used. 2: Separate tail cables must be provided for each track circuit end. 3: Disconnection Boxes should be mounted in a permanent Green Zone as defined in GO/RT3073.

Note Note

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Figure E13

Tail Cable To Lineside Apparatus Housing

Rail 2 Duplicate Track Cable Figure E14

Rail 2 Lead

Rail 1 Lead

Rail 1 Duplicate Track Cable

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10 Arrangement of Track Lead Rail Connections (Except Jointless)

Figure E15 and Figure E16 show typical arrangements of rail connections either side of an insulated joint. Figure E15 uses 90mm diameter orange pipe and is the preferred arrangement, except where the pipe is unable to be threaded under the rail, (eg. tunnels and other areas of restricted use). Figure E16 shows the alternative method where the cables are clipped to the top of the sleepers. In both cases, duplicated single core 2.5mm²(f) flexible cable, fitted with moulded rubber connectors, is the preferred arrangement to be used between the disconnection box and the rail. It is terminated on the four foot side of the rail. Under no circumstances should the track leads of different track circuits share a common rail connection. Note Combining two track circuits into one 4 core cable is not permitted.

If required, in order to avoid vandalism, the disconnection box can be replaced by a heat­shrink jointing kit. Track lead arrangements for jointless track circuits are described in the relevant section dealing with the particular design.

IRJ

A

C

Traction Return Bond

w

Y

B

D

X

Z

IRJ

Dis Box

On non-electrified lines the first bay to be left clear

Dis Box

Cable Route

Note Dis Boxes should be mounted in a permanent Green Zone as defined in GO/RT3073. Figure E15

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IRJ

A

C

Traction Return Bond

W

Y

B

D

X

Z

IRJ

Dis Box

On non-electrified lines the first bay to be left clear

Dis Box

Cable Route

Note Dis Boxes should be mounted in a permanent Green Zone as defined in GO/RT3073. Figure E16 Description Pipe, Medium Density, Orange, 6 metres x 90mm Clip, Pipe for 90mm o/d pipe Fastaway Clip, 6.5mm for 2.5mm²(f) cable Moulded Flexible TC Lead 2.5mm²(f): 3.0 metre 4.5 metre 6.5 metre 8.0 metre 30.0 metre Disconnection Box for Track Circuit Stake for Disconnection Box 760mm Long Stake for Disconnection Box 1070mm Long Cable Joint Kit, 1 x 2.5mm²(f) single to 1 x 2.5mm² single Cable Joint Kit, 2 x 2.5mm²(f) single to 1 x 2.5mm² two core Cable Joint Kit, 2 x 2.5mm²(f) single to 1 x 2.5mm² single Cable Joint Kit, 4 x 2.5mm²(f) single to 1 x 2.5mm² two core

Catalogue No. : : : 86/44141 86/44140 86/43489

: : : : : : : :

86/44022 86/44023 86/44024 86/44025 86/44026 86/43877 86/10751 86/10751

: : : :

54/15875 54/15873 54/36101 54/36102

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11 Fishplate Bonding

The method and components described in this section are to be used to improve the reliability of the electrical connection between pieces of rail which are already in casual electrical contact by virtue of their construction. Whilst the most obvious item in this category is the non­insulated fishplate type rail joint on all non­electrified and a.c. electrified lines, this method of bonding extends to elements of S & C, such as crossings, wing rails etc, where the components are also bolted together without intervening insulation. On d.c. or dual a.c./d.c. electrified lines, it is to be used on the signal rail only of single rail track circuits. Bonding of fishplates in the traction return rail of d.c. electrified railways is the responsibility of the Electric Traction Engineer. 11.1 Standard Fishplate Arrangement Two 7.2mm holes, 76mm apart, are drilled through the rail web in the first sleeper bay each side of the joint. The holes should be 57 ±2mm above the base of the rail. The bonds should generally be fitted on the four foot side of the rail using channel pins and run close to the base of the rail, as shown in Figure E17. The short exposed end of the bond should be folded flat and hammered against the rail. Bonds should not be threaded through the fishplates or rail fastenings. In areas prone to vandalism the bonds may be passed under the rail so that they are less vulnerable; when this is done one end of each bond is attached to the inside of the rail and the other end to the outside. However, bonds should not be passed to the outside of the rail if there is a conductor rail on that side. Catalogue numbers are as follows: Description Bond, solid steel, galvanised, 4.29mm x 1670mm Channel Pin to BRS-SE33

76 535 535 76 A B

Catalogue No. : : 86/44149 86/44012

A

B

Running Edge Channel Pin

7.2mm DIA. Hole

57 ± 2mm

Bond

Figure E17 RAILTRACK E 21

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11.2

Standard S&C Arrangements

11.2.1 Switch/Stock Rail

Switch Rail

Stock Rail

Figure E18 11.2.2 Acute Fabricated Crossing

*

*

Parallel Wing Extension

Figure E19 If a parallel wing is fitted, holes marked * should have bond leads fitted prior to assembly of vee and before the parallel wing is attached. The leads should be tied along the rail to prevent damage in transit.

11.2.3 Obtuse Fabricated Crossing

Figure E20

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11.3 Fishplates in Concrete Bearer Pointwork Rail to rail fishplate bonding in concrete bearer S & C should be achieved using the same techniques as specified for Standard Jumper Bonding. 11.4 Redundant Insulated Rail Joints Where redundant insulated rail joints cannot be avoided: a) In d.c. traction areas, the Electric Traction Engineer should be requested to install all temporary bonds across IRJs which will carry Traction Return Current. If the bond is to carry track circuit currents only, Galvanised Iron (GI) bonds may be used and be fitted by the Signal Engineer. b) In a.c. traction areas, if either side of an IRJ is a traction return rail, the Electric Traction Engineer should install the temporary bond, but if both sides of the IRJ are signal rails then standard fishplate bonds may be used as a temporary measure. c) In non­electric traction areas, ordinary bonds should be used.

12 Jumper Bonding

This section describes the components and installation of jumper bonds designed to carry track circuit currents only. Apart from special cases of impedance bonds, traction jumpers are the responsibility of the Electric Traction Engineer. Refer to Section 2. 12.1 Standard Jumper Bonding This arrangement should be used on non­electrified lines and on the signal rail only of d.c. or dual a.c./d.c. electrified lines. It should not be used for yellow bonding purposes. Standard jumper bonding uses the same single core cable as used for track terminations (GS/ES 0872 Type C1 2.5mm²(f)) terminated in the rail web, using either the "L" Plate connector or preformed moulded rubber connector. For cable lengths and catalogue numbers see 10. 12.2 Yellow Standard Bonding Yellow standard bonding uses GS/ES 0872, 35mm² cable, identified with a yellow sheath or a yellow sleeve at the termination. The bonds are supplied in various lengths with a moulded rubber connector for connection to the rail at one end and unterminated at the other. Yellow bonds should not be installed more than 20m apart. Catalogue numbers are as follows: Description Moulded Flexible TC Lead 35mm²: 3.0 metre 4.5 metre 6.5 metre 8.0 metre 30.0 metre Jointing Kit For Moulded Flexible TC Lead 35mm² Catalogue No. : : : : : 86/44155 86/44154 86/44153 86/44152 86/44151

:

54/037092

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13 High Voltages

Fix warning signs (Figure E21) to all exposed track circuit capacitors and to the outside of lineside apparatus housings containing high voltage track circuit equipment. Catalogue numbers are as follows: Description Safety sign, yellow triangle "caution risk of electric shock", 50mm wide Safety sign, yellow triangle "caution risk of electric shock", 100mm wide Safety sign, yellow triangle "caution risk of electric shock", 150mm wide Safety sign, yellow triangle "caution risk of electric shock" plastic laminate 300mm x 300mm Catalogue No.

:

56/144135

:

56/144111

:

56/144130

:

56/144611

Figure E21

14 Lineside Apparatus Housing Wiring

For general wiring procedures the appropriate Code of Practice should be consulted. Refer to Codes of Practice within the Track Circuit Handbook for special cases. 14.1 Protection of Terminals Terminals in lineside apparatus housings, dis. boxes, etc and impedance bond terminal boxes should be corrosion proofed using Valvoline Tectyl 506 (Catalogue No. 7/58553) as soon as wiring and testing are complete. Valvoline should not be applied to capacitor adjusting slides, fuse clips or end caps, or the windings of wire­wound resistors.

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15 Impedance Bonds

15.1 Handling Precautions When transporting impedance bonds, they should be lifted only by the lifting lugs or at the defined lifting points. Under no circumstances should any weight be taken on the traction lead terminals or cable lugs as this can result in damage to the insulation, allowing water to enter. Type 3 impedance bonds have positions for lifting lugs to be fitted, which should be removed as soon as the impedance bond has been placed in the track and replaced with the supplied means of protecting the threads. 15.2 Impedance Bond Types and Restrictions Refer to the table in Figure E22

Manufacturer Howells or WBS Howells or WBS WBS SGE WBS WBS WBS SGE GRS

Style WH3 MR or S P3 DE M M2/5 M650/ 75 DD B

Freq. (Hz) 50 50 50 50 50/75 50/75

Function Universal Universal Universal Universal Specific Specific* Specific

Type 3 2 1 I 0 0 0 0 0

Cat No 86/17024 86/17023 88/1237 88/83945

Oil Filled No No Yes Yes Yes

Aux. Coil Ratio 56: 1 56:1 45:1 40:1 42:1 42:1 45:1 42:1 45:1

Weight (Kg) 160 160

Supply N O S

120 230 190 230 230

S O S O O O

88/83948 88/83952

Yes Yes Yes Yes

50 50

Universal Specific

Figure E22 The table in Figure E22 is interpreted as follows: Function Universal Impedance bonds shown as "Universal" may be used for all functions in all styles of track circuit approved for use in d.c. electric traction areas, subject only to their ability to cope with the designed traction current load. Note: Saturation levels and avoidance of particular combinations of bond and track relay, should be considered when replacing bonds of one style with another (see Clause 15.4). The impedance bonds are tuned to 50Hz. For other frequencies, internal resonating capacitors are fitted. Specific Impedance bonds shown as "Specific" are specially set or tuned to perform feed, relay or intermediate functions at a particular frequency. If, in an emergency, an impedance bond is required to perform a different function or operate at the other frequency, it should be re­tuned. RAILTRACK E 25

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*

WBS style M2/5 impedance bonds have been serviced as "Universal" since 1984.

Notes N. (New) - In production and serviced. S. (Serviced) - Out of production, but still serviced. O. (Obsolete) - Out of production and not serviced. Type All new impedance bonds are manufactured to specification BR863, the current rating of which is shown in Figure E23:

Bond Type Type 3 Type 2 Type I Type 0

Traction Current Rating to BR 863

3000A continuous, 4500A for 2 hours 2400A continuous, 3600A for I hour 950A continuous, 1100A for I hour (Not to BR863) (Not to BR863)

Figure E23 On high current dc. traction lines, ie. where classes 92, 373, 465 and 471 locomotives and multiple units run in revenue­earning service, only Type 3 impedance bonds fitted with six side leads (three on each side) are to be used. On other lines, any type of impedance bond may be used and need only be fitted with two side leads. 15.3 Sleeper Spacing The sleeper spacing required for impedance bonds is shown in Figure E24.

Bond Style WH3 MR or S P3 DE M M2/5 M6 DD B

Type 3 2 1 1 0 0 0 0 0

Sleeper Centres (mm) 650* 750** 635 585 700 700 700 725 710

Figure E24 * The fixing centres for Type 3 impedance bonds is 650mm. However, any spacing between 570mm and 730mm will be satisfactory as the impedance bond is not fixed down at the terminal box end (see Figure E26). ** S and MR impedance bonds are also only fixed at one end, therefore the spacing of the sleepers is not critical RAILTRACK

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15.4 Impedance Bond Interchangeability When an impedance bond is changed for another type, it is usually necessary to change some or all of the associated connections. Figure E25 is included as a guide to the items affected. The preferred replacement is shown shaded. As well as physical interchangeability, the replacement bond will need to be sufficiently rated for the peak and continuous traction currents that occur on that line. Imbalance in traction return currents will tend to apply a proportion of any interference content to track circuit receivers, which under particular conditions could lead to a wrong side failure. One mechanism whereby imbalance is detected, is due to saturation of the impedance bonds. As the difference between the traction currents flowing through the impedance bond's half windings increase, the transformer action of the impedance bond becomes less efficient as it is driven into saturation, thereby suppressing the track circuit voltage. The operation of the track circuit will become unreliable, but some protection against wrong side failure of the track circuit is provided. The level of imbalance current required to saturate impedance bonds is roughly proportional to their rating, with higher rated type 3 bonds able to withstand greater imbalance current levels than type 2 bonds for example. This saturation of impedance bonds leading to right side failure of the track circuit, can provide useful protection against wrong side failure due to traction interference. Therefore, care should be applied when replacing one type of bond for another, as the tolerance to imbalance may be increased, but at the expense of detection of situations where track circuits become exposed to traction interference which could lead to wrong side failure. Additionally, certain bond/relay combinations should be avoided as they may create problems in correctly setting up 50Hz a.c. double rail track circuits. In particular, G4 relays should not be used with type 2 or type 3 bonds. If the track relay is a style CE391, the recommended replacement impedance bond is style DE, but if this is not available, it will usually be necessary to change the relay and base to a VT1. It is also recommended that the impedance bond at the other end of the track circuit is changed in order to get a satisfactory adjustment, particularly if a style B impedance bond is being displaced.

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TABLE OF IMPEDANCE BOND INTERCHANGEABILITY Old Impedance Bond Component New Impedance Bonds

WH3 Side leads MR Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable Side leads Plate Tail cable C C E E C E C D R E D R C D R C D R C D R C D R C D R

P3 E C J C C J E E E C D R T C E C D R C D R C C E C C R

DE T C J C C J C D R E E E C C R C D R C D R C C E C C J

M2/5 C C J T C J T C J T D J T E E E E E E E E T D E T T J

S

P3

DE

M

M2/5

M6

DD

B

Legend E Existing component can be re­used. C Existing component to be changed. T Existing component can be used temporarily. D Existing re­drilled and/or cut J Joint required. R Re­use (may be jointed using kit, Railway Catalogue No S411S289. Figure E25

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15.5 Impedance Bond Spares and Repairs Maintenance and local stock holding will generally be made easier if different styles of impedance bond are not intermixed within a track circuit. Surplus and defective impedance bonds should be returned intact to the local Infrastructure Store for servicing. New or re­serviced impedance bonds are available to order from the stores organisation. In an emergency, ie. if a possession or a replacement impedance bond cannot be obtained, replacement of faulty parts may be carried out in­situ in some cases. The following spare parts are available. Railway catalogue numbers are given where applicable: 15.5.1 Style WH3 Not repairable. 15.5.2 Style MR Obsolete, parts out of production. 15.5.3 Style S Description Terminal box (CD1073) Terminal block (WBS Drg B41464/1) Terminal label (WBS Drg J14676/­ Cable gland 25mm (Hawke type 300 P25) Cable gland 20mm Blanking grommet 25mm (RS605­677) Blanking grommet 20mm (RS 605­661) Resilient mounting 15.5.4 Style P3 Description Coil, universal Covers, main Covers, terminal box Gasket, main cover Gasket, terminal box cover Plate lug centre connection Seal rubber, side lead A/57117/1 Terminal assy. CD.1055/S 15.5.5 Style DE Description Coil, auxiliary (2BA lugs) Coil, auxiliary (OBA lugs) D4/21048A Cover, main Cover, terminal box Gasket main cover Gasket terminal box cover 15.5.6 Style M Description Coil, auxiliary, feed or relay Coil, auxiliary, resonated

: : : : : : : :

Catalogue No 86/43866 N/A N/A N/A 54/109127 N/A N/A 86/117018

: : : : : : : :

Catalogue No 88/49566 88/84009 88/84010 88/84011 88/84012 88/27761 88/26415 88/84013

: : : : : :

Catalogue No 88/2308 88/84038 88/84039 88/84040 88/84041 88/84042

: :

Catalogue No 88/83976 88/2321

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15.5.7 Style M2/5 Description Coil, condenser Plate, lug, steel (pairs with screws) for fitting side connections

: :

Catalogue No 88/26065 88/83987

15.5.8 Style M6 Obsolete, parts out of production. 15.5.9 Style DD Description Coil, auxiliary Gasket, main cover 15.5.10 Style B Description Coil auxiliary Terminal box Cover, terminal box 15.5.11 General Spares Description Sealing Compound Red Hermabte no. 5400 Oil, insulating (impedance bonds) 2.5 litre

: :

Catalogue No 88/83553 88/27047

: : :

Catalogue No 88/83958 88/25802 88/83959

: :

Catalogue No 7/60180 27/13802

16 Impedance Bond Installation

CAUTION: Care should be taken to avoid trapping fingers when handling impedance bonds. 16.1 Type 3 Impedance Bond Type 3 impedance bonds supplied to BR863 have blanking plates, grommets or plastic plugs in the terminal box holes, together with one M25 gland, for 2c Type C2 2.5mm²(f) and four M20 glands, for single core Type C1 2. 5mm²(f). The impedance bond is also supplied with resilient mountings, either fitted or supplied separately. The resilient mounting feet comprise two portions and, if not already fitted, should be glued together using Araldite Rapide or Araldite (Railway Catalogue No. 7/103330). The cable glands should be fitted as required and the internal lock nuts glued with Araldite. If unused holes are fitted with plastic plugs, these should be replaced with threaded blanking plates. Surplus blanking plates, grommets and glands should be retained as spares. In instances where the auxiliary coil box is prone to water accumulation, a 3mm hole may be carefully drilled in the bottom of the terminal box and all swarf cleared away. The bond is now ready for installation. The standard installation arrangements for Type 3 bonds on concrete or wooden sleepers (Howells or WBS Style WH3) are shown in Figure E26, Figure E27 and Figure E28.

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After installation, it is particularly important to ensure that all glands are securely tightened onto the cables and that all unused entry holes are properly sealed. This will reduce the incidence of failures resulting from an accumulation of brake dust on the terminal block and tuning capacitor. Debris exclusion covers should be fitted to Type 3 bonds: For WBS WH3 Railway Catalogue No 86/17030 For Howells WH3 Railway Catalogue No 86/17031 Note Under no circumstances may a bond be commissioned unless all glands are correctly fitted and any unused holes are fitted with a threaded blanking plate.

For drilling of holes in concrete sleepers/bearers, see GK/RC0754 Part D. Figure E26 shows the Typical Pin Brazed Arrangement for the Type 3 Impedance Bond.

Arrangement This Side of IRJ To Be Used For Double/Single & Double/Double Layout For Type 3 Bond 85 240 85 200 I.R.J.

For Arrangement This Side of IRJ See Figure E27 & Figure E28

200

C L

Bond Not Secured To sleeper At This End

For Busbar Packing See Section E17 Cable Lugs Secured on Top of Bond Lug For Busbar Details See Section E17

For Cable Lengths See Section E18

Holes for Temporary Jumpers When Required Cable Lugs Secured Underside of Bond Lug

All Cables To Be Clear of Tamping Zones See Section E6 I.R.J.

200

85

240

85 200

For Rail Connections see Section E8

For securing bond on concrete sleepers drill on centre line at 400 ctrs 12 dia and secure with Hilti heavy duty anchors HSA 12x 110 Hilti code 66337 (2 OFF). For wooden sleepers use coach screws 5/8" x 6". Catalogue No 35/13950. Screws not to be driven fully home but left approximately 25 above bond lugs.

Figure E26

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Figure E27 shows the Busbar Pin Brazed Connections for Plain Line/Long Switch Fronts.

Arrangement This Side of IRJ To Be Used For Double/Single & Double/Double Layout For Type 3 Bond I.R.J. For Busbar Details See Section E17 For Busbar Packing See Section E17 200 For Busbar Restrictor Arrangement See Figure E43 Arrangements This Side of IRJ To Be Used For Double/Single Layouts

For Rail Connections see Section E8

200

Notes All Cables To Be Clear of Tamping Zones See Section E6

For Cable Lengths See Section E18 200 I.R.J.

Hole Positions In Busbar To Be Drilled On Site 200

155 240

155 240

For Rail Connections see Section E8

Figure E27

Figure E27 shows the Busbar Pin Brazed Connections for Short Switch Fronts.

Arrangement This Side of IRJ To Be Used For Double/Single & Double/Double Layout For Type 3 Bond

Arrangements This Side of IRJ To Be Used For Double/Single Layouts S S

For Rail Connections see Section E8 I.R.J. For Busbar Details See Section E17 For Busbar Packing See Section E17

For Busbar Restrictor Arrangement See Figure E43

For Cable Lengths See Section E18 I.R.J. 155 240 Notes All Cables To Be Clear of Tamping Zones Section E6 155 240

Hole Positions In Busbar To Be Drilled On Site For Rail Connections see Section E8

Figure E28

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16.2 Type 2 Impedance Bond The standard installation arrangements for Type 2 (Style MR or S) impedance bonds on concrete or wooden sleepers are shown in Figure E28 and Figure E29.

Plastic Pipe

Arrangement This Side of IRJ To Be Used Double/Single & Double/Double Layout For For Type 2 Bond

Arrangements This Side of IRJ To Be Used Double/Single Layouts For S S

I.R.J. For Busbar Details See Section E17 For Busbar Packing see Section E17 For Busbar Restrictor Arrangement see Figure E43 Hole Positions In Busbar To Be Drilled On Site

Bond Not Secured To sleeper At This End Type 2 Bond For Cable Lengths See Section E18

This Drawing Should Only Be Used For Renewal of Individual Components in Existing Installations I.R.J.

For Rail Connections see Section E8 S S

Notes All Cables To Be Clear of Tamping see Section E6 Zones

For securing bond on concrete sleepers drill on centre line at 400 ctrs 12 dia and secure with Hilti heavy duty anchors HSA 12x 110 Hilti code 66337 (2 OFF). For wooden sleepers use coach screws 5/8" x 6". Catalogue No 35/13950. Screws not to be driven fully home but left approximately 25 above bond lugs. Figure E29

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16.3 Type 1 Impedance Bond The standard installation arrangements for Type 1 (Style P3 or DE) bonds are shown in Figure E30 and Figure E31. On timber sleepers, the bond should be fixed using 6" x 5/8" coach screws (railway cat no: 35/13950). Approximately 25mm clearance between the bond fixing lug and the underside of the coach screw is required to allow settlement of the sleepers without causing the bond fixing lugs to come under strain. For installation on concrete sleepers, see Figure E36.

Timber Timber

200

76

Track Leads

P3 Track Leads

585 CRS

Figure E30

Timber Timber

76

200

D.E.

76

585 CRS

Figure E31

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16.4 Type 0 Impedance Bond The standard installation arrangements for a Type 0 (Style B, DD, M, M2, M5 or M6) bond is shown in Figure E32, Figure E33, Figure E34 & Figure E35 . On timber sleepers, the bond should be fixed using 6" x 5/8" coach screws (Railway Catalogue No: 35/13950). Approximately 25mm clearance between the bond fixing lug and the underside of the coach screw is required to allow settlement of the sleepers without causing the bond fixing lugs to come under strain. For installation on concrete sleepers, see Figure E36.

Timber Timber

76

200

Track Leads

B

710 CRS

Figure E32

Timber Timber

200

76

Track Leads DD

710 CRS

Figure E33

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Timber

Timber

200

76

Track Leads `M'

585 CRS

Figure E34

Timber Timber

200

76

Track Leads M2. M5.

700 CRS

Figure E35 16.5 Concrete Sleeper Fixing Arrangements The fixing of impedance bonds to concrete sleepers/bearers requires the sleeper/bearer to be drilled off centre. This problem is overcome by using adjustable fixing straps (see Figure E36). Signal Engineering staff are permitted to drill holes in concrete sleepers, however, these may only be drilled on the centre line of the sleeper. If concrete bearers are required to be drilled, prior agreement should be obtained from the Permanent Way Engineer.

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Sleeper Drilled 18 on Centre Line X 95 Deep (Min) Metal Anchor HSL M12/25 Hilti Code 6692 2 Off M20 X 50 Long Hex. Hd. Screw Sleeper Not To Be Drilled

Ø 16

3 X 45 degree Chamfer 30 12 3 Fillet Weld 7.5 Radius " 40 " 40

400

65 140 All Dimensions in mm

18

Typical Arrangement if Impedance Bond Fixing to Concrete Sleepers

Figure E36

16.6 Safety Labelling Warning labels as described in Section 14 should be fitted to the outside of the auxiliary coil terminal box cover.

17 Aluminium Busbars

17.1 Introduction The various layouts and installation arrangements of aluminium busbars are shown on the drawings as described below: Inter­track circuit connections are shown in Figure E37 and Figure E38. Details of busbar lengths and Railway Catalogue Nos. are given in Figure E39, Figure E40, Figure E41 and Figure E42. Busbar drillings for connection to the bond and rail side leads are shown in Figure E28, Figure E29 and Figure E39. Style S impedance bonds are fitted with down­set busbars. Details can be found in Figure E37, Figure E38, Figure E39 and Figure E40. Installation details of the aluminium busbars are shown in Figure E26, Figure E27, Figure E28, Figure E29 and Figure E43. Installation of the busbar to earlier types of impedance bond is shown in Figure E32, Figure E33, Figure E34 and Figure E35.

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17.2 Impedance Bond Lug Plates In the case of the Style P3 impedance bond, the busbar is not secured directly to the impedance bond lug plate as with all other impedance bond types. A separate lug plate (Railway Catalogue No. 88/27761) is required, as shown in Figure E44. This is secured to the impedance bond lugs with four 1¼" x 3/8" hexagon headed BSW bolts, plain spring washers and nuts, which are provided with the impedance bond. 17.3 Packing Pieces The arrangement of packing pieces required between busbar and sleeper is shown in Figure E29. The packing pieces are illustrated in Figure E45. They are not attached to the sleepers but secured to the busbar using No.10 x 1¼" wood screws. 17.4 Busbar Restrictor The busbar is maintained in position by a busbar restrictor arrangement. This comprises a pair of side stops (Railway Catalogue No 88/27760) as shown in Figure E46. The side stops incorporate a steel rod assembly to prevent excessive vertical movement. Installation of the busbar restrictor is shown in Figure E43. 17.5 Impedance Bond Connection Arrangements Figure E37 shows the various connection arrangements to be applied to Type 3 impedance bonds installed in new works. Connections for maintenance replacement of other types of impedance bond are shown in Figure 38.

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Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page E39 of 52

*

* IRJ

*

IRJ

IRJ Intertrack Cables A Item 1 DOUBLE RAIL TRACK CIRCUIT TO NO TRACK CIRCUITED LINES Intertrack Cables A

IRJ

Item 2 Double Rail Track Circuit to Double Rail Track Circuit T.P. Huts or Cross Bonding Sites

T.P. Huts Neg Return B

Substation Neg ReturnB

*

IRJ

*

*

IRJ

*

IRJ Intertrack CablesB Item 3 Double Rail Track Circuit to Double Rail Track Circuit Substations Intertrack Cables B Item 4

IRJ Neg Reinforcing Cable B See Note 9

Double Rail Track Circuit to Single Rail Track Circuits Substations

N.B. This Arrangement is Also Used at Sites Other Than Substations

T.P Hut Neg Return A

Neg Reinforcing CableB IRJ

Substation Neg Returns

T.P. Hut B Neg Return

*

*

*

B

*

IRJ Intertrack Cables A Item 5 Double Rail Track Circuit to Single Rail Track Circuits T.P. Huts Or Cross Bonding Sites. Intertrack Cables B Item 6 Double Rail Track Circuit Intermediate Bond At Substation Intertrack Cables A Item 7 Double Rail Track Circuit Intermediate Bond T.P. Huts Or Cross Bonding Sites

Notes 1 All lugs complete with bolts, nuts and washers for negative cross bonding substations and T.P. hut cable attached to busbar to be supplied and fitted by Electric Traction Engineer. 2 For details of all busbars see Figure E39. 3 For full details of layouts see Figure E26, Figure E27, Figure E28. 4 Traction Return cable sizes : = 240mm2 Aluminium = 800mm2 Aluminium A B 5 Where TI.21 Track Circuits rail bonds require to share the first sleeper bay with the traction return cable, they must be taped to the traction return cable. Orange pipe must not be used 6 The Electric Traction Engineers lugs to be attached to the top of the busbar (Figure E55 for marking jig). 7 Impedance bonds at substations and T.P. Huts to be sited in co-operation with the Electric Traction Engineer. 8 In all layouts a longer busbar may be provided where necessary to accommodate reinforcing cables. * Cross track orange plastic pipe for protection of signalling cables.

Figure E37 Type 3 Impedance Bond Connection Arrangement

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General Information on Track Circuits

Intertrack Cables

A IRJ

T.P. Huts Neg Return A

*

*

IRJ

*

IRJ Intertrack Cables A Intertrack Cable A

IRJ

Item 1 Double Rail Track Circuit to Non Track Circuited Lines

Item 2 Double Rail Track Circuit to Double Rail Track Circuit T.P. Huts Or Cross Bonding Sites

Intertrack Cables B

Substations Neg Return IRJ

B

Intertrack Cables

B

Substations Neg Return B IRJ

*

*

*

*

IRJ Intertrack Cables B Item 3 Double Rail Track Circuit to Double Rail Track Circuit Substations Substations Neg Return B Intertrack Cables B

IRJ Substations Neg Return Item 4 Double Rail Track Circuit to Single Rail Track Circuits Substations B

T.P Hut Neg Return A

Intertrack Cables IRJ

B

Substation Neg Returns

B

T.P. Hut Neg Returns

B

*

*

*

*

IRJ Intertrack Cables A Item 5 Double Rail Track Circuit to Single Rail Track Circuits T.P. Huts or Cross Bonding Sites. Notes 1 All lugs complete with bolts, nuts and washers for negative cross bonding substations and T.P. hut cable attached to busbar to be supplied and fitted by Electric Traction Engineer. 2 For details of all busbars see Figure E39. 3 For full details of layouts see Figure E27, Figure E28. 4 Traction Return cable sizes : Intertrack Cables B Item 6 Double Rail Track Circuit Intermediate Bond at Substation Substation Neg Returns B Intertrack Cables Item 7 Double Rail Track Circuit Intermediate Bond T.p. Huts or Cross Bonding Sites A

A

= 240mm2 Aluminium

B

= 800mm2 Aluminium

5 Where TI.21 Track Circuits rail bonds require to share the first sleeper bay with the traction return cable, they must be taped to the traction return cable. Orange pipe must not be used. 6 The Electric Traction Engineers lugs to be attached to the top of the busbar (See Figure E55 for marking jig). 7 Impedance bonds at substations and T.P. Huts to be sited in co-operation with the Electric Traction Engineer. 8 In all layouts a longer busbar may be provided where necessary to accommodate reinforcing cables. * Cross track orange plastic pipe for protection of signalling cables.

Figure E38

Impedance Bond Connection Arrangements (Other than Type 3)

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17.6 Busbar Details and Layouts Figure E39 shows busbar drilling layouts.

11 2 Holes 12 Dia

55

25 15 41 41

55

44.5

19

44.5

P3

11 4 Holes 14 Dia

41

M,M2,M5

15 6 Holes 14 Dia

55 15

44.5

19

50

19

35 76 100 38 35

M6

15

DD

6 Holes 14 Dia

6 Holes 14 Dia

55 15

51

25

50

25

44.5

100

41

B

DE

15 6 Holes 12 Dia 4 Holes 14 Dia 57 22

50

45

20

100

75

or MR

WH3

6 Holes 18 Dia

Figure E39

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General Information on Track Circuits

Figure E40 gives details of Style S impedance bond busbar and drilling layouts.

4000 Before Bending 220 45 20

# 100

75

# 6 Holes 18 Dia 150 100

90 45 o 75 R

800 Before Bending 20 45 # 220 45 20

75 #

100

75

6 Holes 18 Dia

150

100

90 45 o 75 R

Material

Aluminum Plate 150mm X 6mm to BS 2898(E1) In 4 Metre Lengths to Railway Catalogue No 88/24804 5 Metre Lengths are Available to Railway Catalogue No 88/24805 Holes Marked # are for Temporary Side Lead Connections

Figure E40

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Figure E41 shows the layout of Style S impedance bond busbars.

Busbar Joint

IRJ

IRJ

Busbars: One Long ( Drill and cut as required) and one short

IRJ

IRJ

Busbar: One Long (Cut flush with sleeper edge if required)

Busbar: One Short

Figure E41

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The layout of Style S impedance bond busbar connections is shown in Figure E42

4 x M16 x 50 LG Hex. HD Bolts 4 x M16 Self Locking Nuts. EZP. Recommended Torque 90Nm 8 X M16 Washers

20 Min 50 Max

Note 1 Ensure all Mating Surfaces are Wire Brushed Thoroughly and Coated With Electrolytic Paste (Catalogue No 7/262001) Before Assembly 2 This Drawing to be Read in Conjunction With Figure E40 & Figure E41

Figure E42 The busbar restrictor assembly is shown in Figure E43.

2 X 6mm Starlock Push On Fasteners Uncapped Finish EZP. 6 Dia Rod X 180 Long Steel BS970.070 M20

Busbar See Fig 14 Busbar Side Stops to be Fitted to all Busbars Which Extend Beyond the Second + Sleeper Bed from Bond Except Where a Double/Double Installation Occurs

Busbar Packing Planed Deal Size 150 X 75 X 35

Side Stops Secured: To Timber Sleepers by No 12 X 2" Woodscrews To Concrete Sleepers Drill Sleeper on Centre Line 5/16" Dia X 2" Deep Insert Nylon Rawlplug M8.96.008. Locate Side Stop. Hammer in Steel Round Head Zinc Plated Drive Screw 14 Gauge X 40mm Through 1/4" Phosphorus Bronze Serrated Lock Washer.

Figure E43 E 44 RAILTRACK

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Figure E44 shows the lug plate for style P3 impedance bonds.

248 11

= 41 41 270

= 41

Figure E44

Impedance Bond Busbar Packing (Railway Catalogue No. 88/27772) is shown in Figure E45.

75 32

T

150

Material Planed Deal, End Grain To T Figure E45 Impedance bond busbar side stop details are shown in Figure E46. 50 2 Holes 08 Dia

42 50

30 50 Figure E46 RAILTRACK E 45

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General Information on Track Circuits

18 Side Leads

18.1 Side Lead Manufacture Impedance bond and busbar side leads are manufactured in accordance with Figure E47 & Figure E48 and the tables in Figure E49, Figure E50 & Figure E51. Figure E47 shows the general procedure in diagrammatically form:

45 45

37/2.25 Aluminium Cable Catalogue No 6/116601

1. Strip Back Insulation

OR

2. Crimp Lugs

Heat Shrink Tube with Sealant Catalogue No 55/118332

3. Fit heat shrink tube (where required) and label

Clear heat shrink tube to completely cover adhesive paper label. For colour of label, legend and Railway Catalogue No see Figure E48, Figure E49, Figure E50 and Figure E51. Label size 50 x 20 nom fitted this end only

Figure E47 Figure E48 gives cable lengths (dimension A) for crimped lug and busbar connections. It should be used in conjunction with the cables in Figure E49, Figure E50 and Figure E51 which give details for each group of cables (green, white or orange group) according to the rail connection.

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Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page E47 of 52

B Item 1

H or E

B

Item 2

H or E

C Item 3 / 4

A

A

A

A

D Item 5

A or E

D

Item 6

A or E

D

Item 7

A or E

A

A

A

D

Item 8

A or E

F

Item 9

A or E

D Item 10

A or E

A

A A

A or E G H or E G

A

C

Item 11/12

Item 13/14

Item 15

E

A

A

A

Note The relative position of the lugs is different on items 1 & 2, 5 & 6, 7 & 8 and 9 & 10. Cable End Connectors are listed below with the (former) Southern Region Drawing No. and Railway Catalogue No. Connector A B C D E F G H Type Rail Lug 50° (Pin Drive) Bond Lug (P3) Bond Lug (DD & DE) Bond Lug (M, M2, 5 & 6) Rail Lug (Stud Fixing) 20° Bond Lug (B) BusBar and Bond Lug (S, MR & Type 3) Rail Lug 20° (Pin Drive) SR Drawing No ME72-86 ME72-88 ME72-92 ME72-89 M39-34/1 ME72-91 ME72-107 M39-34/2 Catalogue No. 55/27630 55/27629 55/27626 55/27627 54/39307 55/27625 55/27631 55/27614

Figure E48

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Figure E49 gives details of Green Group Cables (For Connection to Cembre Studs). Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Cable Connection P3 Bond to Rail Top P3 Bond to Rail Bottom Busbar to Rail Long Busbar to Rail Short M Bond to Rail Top M Bond to Rail Bottom M2, 5 & 6 Bond to Rail Top M2, 5 & 6 Bond to Rail Bottom B Bond to Rail Top B Bond to Rail Bottom DE Bond to Rail DD Bond to Rail S or MR Bond to Rail Busbar to Rail Type 3 Bond to Rail Green Label Legend P3 to M12 Stud Top P3 to M12 Stud Bottom Busbar to M12 Stud Long Busbar to M12 Stud Short M to M12 Stud Top M to M12 Stud Bottom M2, 5, 6 to M12 Stud Top M2, 5, 6 to M12 Stud Bottom B to M12 Stud Top B to M12 Stud Bottom DE to M12 Stud DD to M12 Stud S or MR to M12 Stud Busbar to M12 Stud Type 3 Bond to M12 Stud Catalogue No. 88/29464 88/29463 88/29462 88/29461 88/29460 88/29459 88/29458 88/29457 88/29456 88/29455 88/29454 88/29453 88/29452 88/29451 88/29450 Length (mm) 715 715 # # # # 685 660 # # # # 740 800 740 Lug Types B&E B&E C&E C&E D&E D&E D&E D&E F&E F&E C&E C&E G&E G&E G&E

Figure E49 Figure E50 gives details of White Group Cables (For Connection to Pin Brazed Studs). Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Cable Connection P3 Bond to Rail Top P3 Bond to Rail Bottom Busbar to Rail Long Busbar to Rail Short M Bond to Rail Top M Bond to Rail Bottom M2, 5 & 6 Bond to Rail Top M2, 5 & 6 Bond to Rail Bottom B Bond to Rail Top B Bond to Rail Bottom DE Bond to Rail DD Bond to Rail S or MR Bond to Rail Busbar to Rail Type 3 Bond to Rail White Label Legend P3 to M12 Stud Top P3 to M12 Stud Bottom Not Required Install as Item 14 Not Required Install as Item 14 M to M12 Stud Top M to M12 Stud Bottom M2, 5, 6 to M12 Stud Top M2, 5, 6 to M12 Stud Bottom B to M12 Stud Top B to M12 Stud Bottom DE to M12 Stud DD to M12 Stud S or MR to M12 Stud Busbar to M12 Stud Type 3 Bond to M12 Stud Catalogue No 88/29477 88/29476 N/A N/A 88/29475 88/29474 88/29473 88/29472 88/29471 88/29470 88/29469 88/29468 88/29467 88/29466 88/29465 Length (mm) ( 665 665 N/A N/A # # # # # # # # # 725 665 Lug Types B&E B&E N/A N/A D&E D&E D&E D&E F&E F&E C&E C&E G&E G&E G&E

# Size not determined Figure E50 E 48 RAILTRACK

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Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page E49 of 52

Figure E51 gives details of Orange Group Cables (For Pin Drive Connections). Note Orange Group cables are shown for reference only ­ preferred rail connection is by 12mm dia. stud (pin brazed or Cembre).

Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Cable Connection P3 Bond to Rail Top P3 Bond to Rail Bottom Busbar to Rail Long Busbar to Rail Short M Bond to Rail Top M Bond to Rail Bottom M2, 5 & 6 Bond to Rail Top M2, 5 & 6 Bond to Rail Bottom B Bond to Rail Top B Bond to Rail Bottom DE Bond to Rail DD Bond to Rail S or MR Bond to Rail Busbar to Pin Drive

Orange Label Legend P3 to Pin Drive Top P3 to Pin Drive Bottom Busbar to Pin Drive Long Busbar to Pin Drive Short M to Pin Drive Top M to Pin Drive Bottom M2, 5, 6 to Pin Drive Top M2, 5, 6 to Pin Drive Bottom B to Pin Drive Top B to Pin Drive Bottom DE to Pin Drive DD to Pin Drive S or MR to Pin Drive Busbar to Pin Drive

Catalogue No 88/29477 88/29476 N/A N/A 88/29475 88/29474 88/29473 88/29472 88/29471 88/29470 88/29469 88/29468 88/29467 88/27723

Length (mm) 765 715 1070 690 765 715 685 660 690 690 765 485 740 800

Lug Types B&H B&H C&A C&A D&D D&D D&A D&A F&A F&A C&A C&A G&A G&H

Figure E51 18.2 Side Lead Connection In order to minimise imbalance of traction return current in the impedance bond traction coil, every attempt should be made to ensure electrical balance of the two sets of rail to impedance bond connections. Only aluminium conductors should be used. Copper and aluminium side leads should not be mixed on the same impedance bond as they have different characteristics and the bond will become unbalanced. When a Type 3 impedance bond is used at a site requiring only two side leads these should be connected to the impedance bond lugs using the two holes nearest to the impedance bond casing. At all sites where the impedance bond lugs are at different heights, the side lead connections to the higher lug must be fixed to the underside of the lug. If only the side leads on one side of the impedance bond are renewed, the balance should be checked afterwards, as the new ones may have been installed with a high resistance or the existing leads on the other side may not be as good as the new ones. Before any connections are made to the aluminium plate, any burrs or protrusions should be removed from the mating surfaces of the plate, lug, washers and nuts. A wire brush or steel wool should then be used to make these surfaces clean and bright.

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General Information on Track Circuits

All contact surfaces should be coated with a uniform layer of jointing paste (Catalogue No. 7/26200) immediately after cleaning and any surplus cleaned away after tightening. The paste prevents moisture filling the resultant air spaces between the dissimilar metal surfaces, preventing corrosion which occurs very rapidly, particularly when aluminium is exposed to air or moisture. Where screw and nut connections are made to aluminium plate, eg. the aluminium busbar or P3 impedance bond lug plate, it is essential that mechanical connections are not over-tightened. This is because aluminium displays the property known as ``cold flow" under pressure and if a certain pressure is exceeded, a flow away from the pressure area occurs and the connection becomes loose, resulting in a high resistance connection. Details of side lead/busbar connections and torque values are shown in the tables in Figure E52 and Figure E53. Where possible, the side lead connections should be tested, using a millivolt meter in accordance with GK/RC0754 Part G.

Type of Impedance Bond

Type Of Connection Busbar(Item) Side lead (Item)

Type 3 MR B M P3 DE DD S

D D A A A A A D

E E C A C B A E

Figure E52

Item A B

Description M12 x 50 Long Hex Hd Screw, Steel EZP M12 x 70 Long Hex Hd Screw, Steel EZP M12 Nut, Lock (Bent Beam) Steel EZP M12 Washer, Steel EZP M10 x 50 Long Hex Hd Screw, Steel EZP M10 Nut, Lock (Bent Beam) Steel EZP M10 Washer, Steel EZP M16 x 50 Long Hex Hd Screw, Steel EZP M16 x 70 Long Hex Hd Screw, Steel EZP M16 Nut, Lock (Bent Beam) Steel EZP M16 Washer, Steel EZP

Torque Setting 30Nm 30Nm

Catalogue No. 35/101102 35/101142 03/180167 03/190932 35/100842 03/180166 03/190930 35/101272 35/101312 03/180168 03/190936

C

16Nm 60Nm 60Nm

D E

Figure E53

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Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page E51 of 52

A label with the legend "TRACTION VOLTAGE DO NOT REMOVE THIS LEAD" (see Figure E54) should be attached to or alongside all impedance bond leads at substations, TP huts and TIR sites. These cables are identified on the Bonding Plan as described in GK/RC0754 Part C.

TRACTION VOLTAGE

DO NOT REMOVE THIS LEAD

Red Lettering on White Background Figure E54 18.3 Side Lead Removal An insulated bond punch (Railway Catalogue No. 39/48850) is available and should be used for the removal of side leads from the rail where they are pinned in 22mm or 7/8" holes. This punch may be used adjacent to the conductor rail provided the Railway Group Standard Code of Practice is adhered to. To prevent arcing whilst side leads are being removed or reconnected, particularly where bolted stud connections exist, a temporary jumper of a size equivalent to the side lead being removed, should be connected between the aluminium plate and the rail concerned before the last lead is disconnected. If the impedance bond side lead is identified by a label as shown in Figure E54, it can only be disconnected under an absolute electric traction isolation and in accordance with GK/RC0754 Part D.

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General Information on Track Circuits

19 Traction Negative Return Jumpers

These are supplied by the Electric Traction Engineer and are connected to the aluminium busbar by Signal Engineering staff in accordance with GK/RC0754 Part D. A marking jig (see Figure E55) should be utilised for marking out the busbar for drilling.

20mm

To Be Suitably Drilled and Riveted

191.0mm

63.5mm

50 mm

50

150 mm 150 mm

50 mm

63.5mm

16.5 mm

4 Holes at 17.5 mm Dia.

NOTES 1. bond busbar.) 2. 3. 4. Material is aluminium plate 150 x 6 (Off cut from impedance

Remove all burrs and sharp edges. Jig must be located in the centre of the bed. This jig is for marking out only.

Figure E55 A label with the legend "TRACTION VOLTAGE DO NOT REMOVE THIS LEAD" (see Figure E54) should be attached to negative return jumpers at substations, TP Huts and TIR sites. Such leads may be disconnected only under an absolute traction isolation and in accordance with GK/RC0754 Part G.

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Part F Instrumentation Description and Use

1 Introduction

This section gives details of the tools and instrumentation available for general use on track circuits. Instruments designed to be used with particular designs of track circuit can be found in the relevant Code of Practice within the track Circuit Handbook.

2 Multi­meters

2.1 Types In general, both analogue and digital multi­meters can be used when testing track circuits. Analogue Meters: Description Lineman's AVO HD6 Catalogue No. 86/11001 (No longer available)

:

Digital Meters: Description Megger Instruments M2006 Carrying Case Test Lead Kit Catalogue No. 40/56003 40/56016 40/17758

: : :

Digital meters will usually require a loading resistor of 150k (Catalogue No. 86/11041) fitted to the meter to ensure that a load current is drawn when used on voltage tests.

3 The Universal Shunt Box

3.1 Description Various designs of track circuit shunt box have been produced over the years, some early designs being incapable of coping with the power dissipation requirements when shunting higher powered track circuits. The only design described in this handbook is the current standard design, which is suitable for use on all track circuit designs (Figure F1). Description Universal Track Circuit Shunt Box Catalogue No. 40/5450)

:

Figure F1 RAILTRACK F1

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General Information on Track Circuits

The shunt box has two resistance selection dials: 0 - 9 and 0 - 0.9 which are additive to give a combined range of 0 - 9.9 in 0.1 steps. In order to avoid overheating when left connected, the selected resistance is only placed between the test leads when the button is pressed. The unit comes complete with connecting leads fitted with 4mm plugs, and with two rail clamps for making attachment to the rail foot. These clamps have upper and lower contact points and should be attached to a section of cleaned rail foot without over tightening. The contact points should be replaced if they become blunt. 3.2 Drop Shunt Test

Test: 1 Connect the shunt box across the rails at the relay end of the track circuit. 2 To ensure that the clamps make a good electrical contact with the rails, connect a voltmeter between the rail heads. With zero ohms set on the shunt box and the button or switch operated, ensure the rail to rail voltage falls to zero. 3 Set the shunt box to maximum resistance. 4 Whilst keeping the button depressed, steadily reduce the resistance value until the track relay front contacts are fully open and remain open. The value of drop shunt can then be read directly from the shunt box. The following points should be borne in mind: a) Track circuits do not react instantly to changes in shunt value and time should be allowed for the relay to respond (2-3 seconds is adequate). It is obviously impractical to start at 9.9 and reduce in 0.1 steps at 3 second intervals. Do a preliminary test by setting the 0 - 0.9 selector to 0 and stepping down the 0 - 9 selector to identify the approximate value. Set the 0 - 0.9 selector to 0.9 and step down to obtain the exact value. For example, if the relay drops at 1.0 on the preliminary test, the actual value lies between 1.0 - 1.9. Pick­up Shunt Test

b)

3.3

Test: 1 Connect the shunt box as for the drop shunt test and set both resistance selector switches to 0.. 2 Whilst keeping the button depressed, steadily increase the resistance value until the track relay front contacts just close. The value of pick­up shunt can then be read directly from the shunt box (as for the Drop Shunt Test, similar techniques of delayed stepping and preliminary approximation should be used).

4 Rail Clip Insulation Tester

The vast majority of concrete sleepered track comprises a resilient insulating pad between the underside of the rail and the sleeper, with the rail secured on each side by a clip bearing on the rail foot. Insulation is maintained by plastic pads between the clip and the rail foot. F2 RAILTRACK

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Vibration causes the clip to wear through the pad, putting the rail in electrical contact with the concrete, which degrades the ballast resistance, and, if the track circuit is d.c. operated, may increase the levels of residual voltage. The degradation occurs gradually and identification of the failed insulations can be difficult. The Rail Clip Insulation Tester, sometimes known as "PRIT" or "K9", consists of a unit with an extending handle, which can be rolled along the rail head (see Figure F2). Metal brushes mounted on each side "sweep" the rail clips, measuring the rail to clip insulation. Low values are indicated by an audible alarm. Description Rail Clip Insulation Tester Catalogue No. 40/17741

:

4.1 Operation In d.c. traction areas, the machine must not be used on the rail adjacent to the conductor rail unless an isolation has been obtained. The brushes must be fully retracted and the insulated brush guards fitted before lifting over conductor rails.

Figure F2 4.1.1 Preparation Set the brushes to the correct height. The unit is equipped with "on/off" and "polarity change" switches on the chassis and "test" and "silence alarm" buttons on the handle. Switch "on" and set the "polarity change" switch to +ve. Press the "test" button, note the continuous alarm tone and then silence it by pressing the "silence alarm" button. If no alarm is given, or if the alarm sounds only when the "test" button is depressed, the battery should be replaced with type PP9 or equivalent and the unit re­checked. 4.1.2 Use Push the unit along the rail. When an alarm is received, press the "silence alarm" button and check by re­ sweeping the suspect fastening. Turn the "change polarity" switch to -ve and re­sweep: If an alarm is received, the clip is faulty; if there is no alarm, the clip on the other rail is suspect. RAILTRACK F3

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General Information on Track Circuits

The clip assembly should then be plainly marked for attention by the Permanent Way Engineer. The brush carriers can be raised/lowered to cater for flat or Pandrol type rail clips by moving the brush carrier handle to its vertical position to release the locking mechanism. Care must be taken to ensure that the rollers of the unit do not straddle any IRJs, causing "flicking" of adjacent track circuits.

5 Track Circuit Fault Detector

Short circuits between the rails can be difficult to locate, since, except for audio frequency types, the short circuit results in an identical drop in rail voltage along the length of the track circuit and gives no clue as to its physical location. Without the Track Circuit Fault Detector, it would often be necessary to sub­ divide the trackwork to locate the faulty section. The detector is designed to be used on the trackwork of a track circuit where the feed and relay have been disconnected. It consists of two portable battery powered units: a transmitter and a receiver. Transmitter This is housed in a box incorporating an "on/off" switch and an LED indication. Yellow leads with clips are provided to connect the unit across the rails or lineside apparatus housing links. It is battery powered and outputs an intermittent high frequency voltage. Receiver This is housed in a box incorporating an "on/off" switch and an LED indication. It is battery powered and incorporates an internal aerial, amplifier and loudspeaker. When the receiver detects a signal from the transmitter it outputs an audible tone.

Before commencing to test the bonding of a track circuit, the track circuit fault detector should be checked as follows: a) The transmitter leads should be connected together and the transmitter switched on. b) The receiver should then be switched on and held near the transmitter leads; an audible tone should be heard emitting from the receiver (this simple test will prove that the fault detector is working correctly). c) The feed and relay ends of the track circuit under test should be disconnected. With jointless track circuits, the track circuits either side of the track circuit under test should also be shorted out. d) The transmitter should then be connected across the rails at the feed end and switched on. The receiver is switched on and held near the rail; an audible tone should be heard emitting from the receiver. No tone may indicate a bad connection to the rails. If the rail connections are good, the fault is an open circuit, which may be found in the conventional manner. If an audible tone is heard, the receiver should then be carried along the track near to the rail and when the receiver passes the short circuit, a distinct drop in the volume of the tone will be noted.

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e) With audio frequency track circuits it may not be necessary to disconnect the feed, as the receiver will detect the steady tone of the feed frequency until the short circuit is passed. If this method does not prove successful, the transmitter should be used in the conventional manner. f) The rail impedance limits the useful range of the device (as measured from the transmitter). Where this occurs, the transmitter is simply moved to another position within the track circuit and the test repeated.

6 Mark 4 Direct Reading Phase Angle Meter

Details are contained in GK/RC0757 Part E.

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Part G Testing and Commissioning

1 Introduction

The requirements for testing and commissioning of track circuits are detailed in the following: New Works Maintenance/Fault Finding : : GK/RH 0730 GK/RH 0740

Details of available instrumentation and its uses are given in Part F. This Part details the general requirements for testing and commissioning. Reference should also be made to the Testing & Commissioning Part of the Code of Practice for the particular track circuit design involved.

2 High Voltages

Ensure that warning signs (Figure E21) are fixed to all exposed track circuit capacitors and to the outside of lineside apparatus housings containing high voltage track circuit equipment. Details of the warning signs can be found in Part E.

3 Lineside Apparatus Housing Inspection

Check that: a) All track equipment is of the correct type, as specified in the wiring diagrams, and that applicable pin code configurations are correct. b) All equipment is correctly labelled. c) There are no prohibited combinations of adjoining or parallel types of track circuits. d) There are no prohibited track circuit equipment combinations. e) A wire count is carried out on all terminations, and the wiring proved correct.

4 Bonding Inspection

Check that: a) The physical positions of all IRJs or track ends are correct, especially those defining overlaps or clearance points. b) The physical stagger between nominally opposite IRJs does not exceed the permissible dimensions, and that no sub­section of the track circuit is shorter than the permitted minimum. c) All rail bonds, rail jumpers, traction bonds, track circuit interrupters and track feed/relay cables are in accordance with the bonding plan and scheme plan, and are secure.

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5 IRJ Inspection

5.1 Testing of IRJs IRJs should be visually checked for indications of insulation deterioration, general condition and rail burring over the insulation. If an IRJ is suspect, a possession of the track circuits concerned should be obtained and the IRJ tested for insulation break­down with the track circuits taken out of service. The metallic components of the IRJ being tested should be cleaned to allow a good electrical contact with the test leads. If the insulation resistance between either plate and rail is less than 2k at 50V, thew joint is likely to fail or has partially failed and requires attention. The Engineering Supervisor should be notified so that arrangements can be made with the Permanent Way Engineer to replace the faulty IRJ. In the case of d.c. track circuits, IRJ's may be tested with the track circuits in service under certain conditions. This procedure is described in GK/RC0755 Part F. 5.2 Prefabricated IRJs Edilon and similar prefabricated IRJs must be tested with a 50V insulation tester prior to installation in the track, taking care that the IRJ assembly is not in contact with any conducting surface. Test: a) Between the two rails. b) Between both fishplates and the two rails. c) Between each bolt and the two rails. The minimum acceptable reading is 500k..

6 Performance Test

a) The track circuit should be energised and adjusted in accordance with the relevant section in this handbook. If difficulties are experienced, refer to the Fault Finding Procedures. b) Ensure that the polarity/phase is correct and that the correct electrical stagger is achieved. c) Track circuit interrupters must be tested by disconnection. d) Ensure that all adjoining track circuits are energised. Remove the feed links of the track circuit under test to check that only the correct track relay or relays respond. Check that any remaining extraneous voltage on the track relay does not exceed that permitted for the particular track circuit design (see the Testing & Commissioning Part in the Code of Practice for the relevant track circuit). e) Set the shunt box to the minimum permitted drop shunt value, and apply sequentially at all extremities and at selected places within any S & C, to prove the functionality of the track circuit bonding; the correct track relay must be seen to drop each time. For jointless track circuits, prove that the theoretical extremities are the actual extremities.

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f) Carry out a correspondence test between the rails of each track circuit and any indications or to the final TPR, where no indications are provided. A track circuit must not be commissioned until the person in charge of S&T work is satisfied that the rail surface is sufficiently free of rust and other contamination to ensure correct shunting.

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Part H Maintenance

1 Introduction

This Part is a general guide to the principles of track circuit maintenance. Procedures specific to a particular design of track circuit are given in the relevant Code of Practice within the Track Circuit Handbook. Instructions regarding maintenance of track circuits are given in GK/RH0740 and GK/RC0241. Track circuit maintenance can be classified into the following activities: a) Routine Examination. b) Drop Shunt Test. c) Full Test.

2 Routine Examination

The objective of the examination is to find/remove potential failures and to ensure that, as far as possible, the track circuit will function satisfactorily until the next examination. The examination is mainly visual and can be undertaken without any need for possession of the track circuit. Any obstructions or conditions likely to prove detrimental to the reliability of the track circuit must be dealt with as soon as possible. The requirements and responsibilities for maintenance and inspection of bonding are laid down in GM/TT0127 and GM/TT0128. Refer also to GK/RT0252 Specific attention must be given to the examination of the following: a) Track cables and jumper cables, their connection to the rail and clearance when passing under other rails. b) Fishplate type bonding, including traction return bonding where provided. c) Impedance bonds and connections where provided. d) Metallic and other conductive debris around insulations and rails. e) Point rodding, signal wires etc, touching or liable to touch either rail. f) Insulation deterioration and rail burring over insulations. g) Rust or other rail contaminants on the surface of the rails. The relay voltage should be checked and compared with the entries on the Track Circuit Record Card. If the value is significantly different from previously recorded values under similar weather conditions, a full test should be conducted.

3 Drop Shunt Test

The commissioning drop shunt test is always carried out with the shunt box connected between the rails at the relay end of the track circuit. However, for routine drop shunt tests on d.c. or a.c. power frequency (50Hz 831/3Hz) track circuits (other than auto­coupled impedance bond types), the RAILTRACK H1

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shunt box may be connected across the track circuit relay links in the lineside apparatus housing. The value of drop shunt obtained at the lineside apparatus housing will usually be higher than that obtained at the rails, the resistance of the relay end track leads being the most significant factor. It is only permissible to undertake drop shunt tests at the track circuit relay links in the lineside apparatus housing. where comparative shunts have previously been carried out both at the rails and at the lineside apparatus housing, and the two values are endorsed on the record card. It is then possible to judge any value obtained at the lineside apparatus housing relative to its theoretical railequivalent. Where such a theoretical value can be seen to approach the minimum acceptable, the test should be verified at the rails. The procedure for carrying out a drop shunt test is detailed in Part F 3.2. A variation in the drop shunt value may be caused by variations in equipment performance, or by expected variations in environmental conditions, with the drop shunt reaching the upper end of its range in wet weather and the lower end in dry weather. If the drop shunt exceeds the maximum value for the track circuit (see the relevant Code of Practice ), it is likely that the track circuit is being shunted by poor ballast or debris. The track circuit should be examined for these faults. If it appears to be in good physical condition, the track circuit equipment should be regarded as failed and the cause of the failure investigated through the fault finding procedure (see the relevant Code of Practice). If the drop shunt is lower than the minimum value for the track circuit (see the relevant Code of Practice), there has been an unexpected equipment failure. The Engineering Supervisor is to be informed, and immediate investigations undertaken to ascertain the cause of the low drop shunt value.

4 Full Test

The full test must be applied whenever alterations are made (eg. relaying, lead/jumper renewal, equipment replacement, adjustment, etc). The full test comprises the following: a) Carry out a Routine Examination. b) At the feed end, measure and record the voltages, currents and other parameters as required on the front of the record card. Any adjustments required must be in accordance with the relevant section of this handbook for the type of track circuit under test. c) At the relay end, with the track circuit clear, measure and record the voltages, currents and other parameters required and enter on the front of the record card. d) Perform a drop shunt test with the shunt box across the rails at the relay end and enter details on the record card. Where the track circuit is of a type able to be routine shunted at the relay links in the lineside apparatus housing, perform a second drop shunt test at this position and endorse the record card with that value. e) Set the shunt box to the minimum for that track circuit and connect across the rails at all extremities of the track circuit, confirming that the track circuit occupies on each occasion. This test must obtain simultaneous track circuit occupation where an overlapping section exists.

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Part J Fault Finding

1 Introduction

This Part gives a general outline to faults common to all types of track circuits; faults caused by electric traction systems or peculiar to a particular track circuit design are given in the appropriate Code of Practice of the Track Circuit Handbook. When clearing a fault, details of all readings and results should be noted, to establish a logical pattern of testing and adjustment. The track circuit record card(s) should always be investigated, as deteriorating readings during maintenance can show the impending failure of a component. When a fault has been located, the relevant tests carried out up to that point should be repeated, as, in the case of multiple simultaneous faults, one fault can mask another. Once a fault has been cleared, the track circuit must be fully tested prior to restoration.

2 Categories of Failure

Track circuit failures fall into the following categories: Right Side: Indication shows occupied with no train in the section. Indication shows clear when a train is in the section, but is caused by a failure of the indication system only; the train is still protected by the interlocking.

Protected Wrong Side:

Unprotected Wrong Side: Track circuit or repeat relay fails to de­energise when a train is in the section; the train is no longer protected by the interlocking. The nature of the failure can be further categorised: Permanent: Intermittent: Failure remains static. Failure is only apparent for short periods.

3 Intermittent Failures

Intermittent faults are often the most difficult to solve, as the failure does not usually remain static long enough to take all necessary readings and observations. The following are possible causes dependent on circumstances: Vibration Vibration caused by the passage of trains can create intermittent high resistance in bonding or intermittent short circuits between the rails (ie. the failure may remain after one train but be cleared by a subsequent one). Trains, or operation of other equipment such as point machines, should be observed on site or on the signalman's diagram; If the failure always occurs with a train at a particular point or coincides with operation of other equipment, that geographic site should be fully investigated.

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Traction Interference

This is usually associated with d.c. traction railways and arises because of the high currents necessary with the low supply voltage. If a failure occurs with trains in certain positions or during times of heavy traffic, the traction return system should be investigated. Due to track circuits being very "earthy", especially during wet weather, trains at certain positions on other lines may affect the rail to rail voltage of a track circuit, causing intermittent failures. An earth fault is usually noticed with a second fault caused by a defective continuity bond. These can cause intermittent continuity problems.

Earth Faults

Broken Rails/Bonds

4 Right Side Failures

When called to a fault, it is first necessary to determine whether the cause lies in the track circuit itself or its associated repeater circuits. This can be resolved by proceeding directly to the relay end and examining the track relay (having confirmed that the track is supposed to be clear !). This section is concerned with fault location in the track circuit itself. 4.1 Types of Fault Since the various track circuits used have differing types of feed units, ranging from a single d.c. cell to complex transmitters, the methods for checking these different feed units are described in the relevant Code of Practice within the Track Circuit Handbook. If the transmitter or feed is found to be functioning correctly, it can then be used to determine the general nature of the fault (ie. short circuit or disconnection). This can be done by taking voltage and current measurements at the feed end as shown in Figure J1 .

V A

Feed Remove Link For Current Measurement

Figure J1

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A disconnection in the series bonding will: a) Reduce the current being fed into the track circuit. b) Reduce the voltage normally dropped across the feed impedance. c) Increase the rail voltage at the feed end. A short circuit will: a) Increase the current fed into the track circuit. b) Increase the voltage dropped across the feed impedance. c) Reduce the rail voltage at the feed end. 4.2 Locating a Disconnection The higher rail voltage can be measured at all positions along the track circuit from the feed end up to the point of disconnection. On the relay side of the disconnection the rail voltage will be very low. Fault location therefore entails walking through and checking the rail voltage to identify the position of the step change in value. The faulty bond etc, can be confirmed by measuring a voltage across it. 4.3 Locating a Short Circuit

4.3.1 General The extent of the change in feed end voltages and currents will depend upon the type of track circuit and the physical position of the fault along the length of the track circuit. Consult the relevant section concerned with the specific type of track circuit, as appropriate. The general position is as follows: a) At d.c. and power frequency a.c., the rail impedance is negligible, and the resulting electrical circuit is constant, wherever the short circuit is located within the track circuit. Thus, any voltage across the rails, permitted by an imperfect short circuit, will be constant throughout the length, giving no clue as to its physical position. b) With audio frequencies and impulses, the rails have significant impedance, and the effect of a short circuit will vary depending upon its physical position. The closer it is to the feed end, the more it will increase the feed current and decrease the rail voltage. In either case, it is not possible to precisely locate the short circuit by simple observation of rail voltage along the track circuit. Other methods available are as follows: 4.3.2 Visual Inspection and Provocation This is particularly useful where track circuit equipment is not responsible. Examples of such a fault include signal wire or point rods touching the rails, and faulty insulation in point connections etc. Connect a meter across the rails and observe its reaction when the item of equipment is provoked (eg. waggle the signal wire or stand on the rods, having first ensured that they will not be operated). In the case of faulty insulations, a hammer blow to the metalwork adjacent to the insulation will often produce sharp changes of rail voltage. Alternatively, the insulation should be carefully dismantled and reassembled.

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4.3.3 Use of Track Circuit Fault Detector The track circuit fault detector comprises a test signal transmitter and a receiver, both units being self contained with their own battery power supply. The detector is designed to be used on a track circuit whose feed has been disconnected and replaced by the test transmitter. However, with audio frequency track circuits, the transmitter may not be required, as the receiver will detect the steady tone of the feed frequency. A full description and details of operation are given in Part F. 4.3.4 Subdivision of Track Circuit This technique is particularly useful for track circuits in S & C where the sections of the track circuit are pieced together with jumper cables. It can be applied in other situations by removal of fishplates and associated bonds in conjunction with the Permanent Way Engineer. Note: This technique must not be applied to a traction return rail or jumper unless the work is under the direct control of the Electric Traction Engineer. Where the feed end test indicates a short circuit and a jumper part of the way through the track circuit is subsequently disconnected, the effect on the feed end will provide clues as to the location of the short circuit. If the short circuit lies between the feed and the disconnected jumper, the feed current and rail voltage will be largely unaffected. However, if the short circuit is between the disconnected jumper and the relay end, the feed end test will now indicate the symptoms of a disconnection. 4.3.5 Faulty Concrete Sleeper Insulations Rails on concrete sleepers are usually insulated from the chair fastenings; the rail sits on a pad whilst clips (eg. Pandrol clips) bear on a plastic insulation piece against the foot of the rail. It is unusual for individual faulty rail insulations to fail a track circuit. Rather, a number of such failures may contribute to a general deterioration of ballast resistance. For the specific investigation of faulty rail insulations, a special test unit; the Rail Clip Insulation Tester, is available. For the applicable description and operating instructions see Part G. 4.3.6 Failure of Insulated Rail Joints Care must be taken when attempting to check the insulation resistance of IRJs in situ due to the parallel path provided by the ballast on either side of the joint. Methods of testing IRJs are given in Part G.

5 Wrong Side Failures

5.1 Rail Surface Permanent or intermittent wrong side failures involving loss of train shunt can occur because of a poor rail surface due to rust, leaf debris, oil film, or crushed coal/sand/ballast. The surface condition should be visually checked throughout the track circuit and suitably cleared if possible. At locations where oil film or rust is excessive and speeds are less than 5 mph (eg. locomotive depots, terminal stations), a stainless steel "zig­zag" strip can be applied to the surface of the running rail by the Permanent Way Engineer.

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5.2 Faulty Track Relay It is possible that a track relay may be mechanically damaged in some way which prevents it properly de­energising. A check should be made to see that the relay operates correctly when a shunt is applied. 5.3 Extraneous Interference It is possible that the track circuit is receiving energy from other than its own feed unit. Disconnect the feed and confirm that the relay voltage is less than 30% of its drop­away value.

5.4 Gaps In Track Circuits This is a problem arising particularly on electric traction railways due to the need to provide parallel alternative paths for traction return current in the rails, but can arise in any situation where the bonding is not in series. It can be seen from Figure J2 that defective bonding in the traction return rail can lead to a wrong side failure; a train between the two disconnected bonds would not shunt the track circuit current. Yellow Bonding is now provided to prevent such occurrences. Where parallel bonding exists, it must be inspected and short circuits applied to confirm correct detection.

Two Disconnections

Figure J2

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References

(Railway Group Standards references correct as at Catalogue 13) Railway Standards Signalling Maintenance Specifications Train Detection Handbook D.C. Track Circuits HVI Track Circuits 50Hz. Track Circuits Signalling Testing Handbook Signalling Maintenance Testing Handbook Symbols for use on Signalling Plans and Sketches Identification of Signalling Related Equipment Train Detection Lineside Signals and Indicators Signalling Design Production Track Circuits Reinforcement of Track Circuit Bonding (Yellow Bonding Production and Modifications of Bonding Plans and the Installation of Bonding on all Electrified Lines except the SE, SC & SW Divisions of NSE. Inspection of Bonds on all Electrified Lines except the SC, SE & SW Divisions of NSE. Maintenance and Inspection of Negative Bonding on the SC, SE & SW Divisions of NSE. Production of Drawings for and the Installation of Negative Bonding on the SC, SE & SW Divisions of NSE. Track Safety Handbook D.C. Electrified Line Instructions. Railway Signaling Cable Impedance Bonds for use with Track Circuits Replacement of Colour Light Signals to Danger Channel Pin for Track Circuit Rail Bonds Stake (Angle) for Track Side Equipment (1070) Stake (Angle) for Track Side Equipment (760) GK/RC0741 GK/RH0751 GK/RC0755 GK/RC0756 GK/RC0757 GK/RH0730 GK/RH0740 GK/RT0004 GK/RT0009 GK/RT0011 GK/RT0031 GK/RT0201 GK/RT0251 GK/RT0252 GM/TT0126

GM/TT0127 GM/TT0128 GM/TT0129 RT3170 G0/RT3091 GS/ES0872 BR863 SSP 62 BRS-SE 33 BRS-SM 104/11 BRS-SM 104/13

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Railway Standards (continued) BRS-SM 318 BRS-SM 319 BRS-SM 320 BRS-SM 374 BRS-SM 375 BRS-SM 376 BRS-SM 411 BRS-SM 622 BRS-SM 848 BRS-SM 849 BRS-SM 2200 BRS-SM 2228 BRS-SM 2240 BRS-SM 2244 Facing Point Layouts Left and Right Hand Drives Single and Double Slip Layout Right Hand Drive Single and Double Slip Layout Left Hand Drive Track Circuit Interrupter Assembly Track Circuit Interrupter Body Unit Track Circuit Interrupter Insulations Taper Pin for Track Circuit Connections Concrete Bearer Layout, S&T Equipment Track Circuit Cables Plate for Rail Connection Track Circuit Cables Flange Clip/Cable Clip for Cable Terminations Rail Clamp Point Lock MK2 Facing Point Layout Single Acting Cylinders & Cast Body Rail Clamp Point Lock MK2 Double Slip Points Layout Single Acting Cyl - Cast Body - A6 Mods Rail Clamp Point Lock MK2 Switch Diamond Layouts Rail Clamp Point Lock MK2 Point Layout with Hydraulic Actuators Tandem Turnout in 113FBV Rail for Cast Body Single Acting Cylinder Rail Clamp Point Lock Facing Point Layout for UIC-541113A Plain Lead Switches Flat Bottom Rail Soleplate for Use with F.P.L.

BRS-SM 2260 MD82017

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