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DW/144

Specification for Sheet Metal Ductwork Low, medium and high pressure/velocity air systems 1998

Copyright © 1998 by the Heating and Ventilating Contractors' Association All rights reserved ISBN 0-903783-27-4 Further copies of this publication are available from: Publications Unit Heating and Ventilating Contractors Association Old Mansion House Eamont Bridge Penrith Cumbria CA10 2BX Tel: 01768 860405 Fax: 01768 860401 e-mail: [email protected]

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THE INDUSTRY STANDARD

Ken Parslow Chairman Executive Committee Ductwork Group 1996-98 For more than a decade-and-a-half, the DW/142 Specification for Sheet Metal Ductwork published by the Heating and Ventilating Contractors' Association has gained national and international recognition as the industry standard against which the quality of ductwork manufacture and installation can be judged. In recent years, however, it has become increasingly evident to the members of the HVCA Ductwork Group that the developments in technology and working practices which have taken place since the drafting of DW/142 have rendered obsolete significant parts of the document. It was an acknowledgement of this state of affairs which led the Technical SubCommittee of the Ductwork Group, ably chaired by Edgar Poppleton, to undertake the task of producing a radically revised specification which would promote best practice and quality standards well into the next Millennium. This new publication - designated DW/144 - represents the direct result of that initiative. The new specification recognises the computer age - with special reference to CAD/CAM procedures and techniques - and the international performance standards established by the Committee for European Normalisation (CEN), as well as the need to update and consolidate much of the information contained in the original DW/142 publication and its Addendum A companion volume. During the drafting process, the Technical Sub-Committee has consulted widely with individuals and organisations throughout the building services and construction sectors in order to ensure that the new specification fully reflected the current the "state-of-theart" in terms both of technical expertise and industry best practice. I firmly believe that this process has resulted in a publication which clearly demonstrates the high level of professionalism which exists within the ductwork community - and I take this opportunity of thanking all those who have contributed to its production. In particular, my thanks go to Edgar Poppleton and his colleagues on the Technical Sub-Committee, to Keith Elphick for the provision of invaluable technical consultancy, and to Ductwork Group secretary Gareth Keller for overseeing the project as a whole.

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MAINTAINING QUALITY

Like most industries, the ductwork sector must be prepared continually to innovate in order to survive and prosper. A key element in that innovation process is the timely review and updating of quality standards to ensure that they continue to offer realistic benchmarks to which all professional individuals and organisations can perform. The development of this new Specification for Sheet Metal Ductwork - designated DW/144 - has been carried out with that objective in mind. In the 16 years since the publication of its predecessor, DW/142 - and in the ten years since the supplementary volume Addendum A appeared many technical advances, changes in working practices and regulatory introductions and amendments have taken place. The common performance standards for ductwork being developed by the Committee for European Normalisation (CEN), for example, had to be taken fully into account during the drafting process. Similarly, notice had to be given to the provisions of the Control of Substances Hazardous to Health (COSHH) and Construction (Design and Management) Regulations, neither of which had been issued when DW/142 was published. It is not possible - nor, I think, desirable - to include in this foreword an exhaustive catalogue of the points of difference between this specification and its predecessor. These will clearly emerge from a detailed reading of the text. I should, however, like to take the opportunity to highlight a few topics which I believe to be of particular significance. They are: · the omission of high-pressure Class D (in order to conform to European practice); · the highlighting of information to be provided by the designer; · the end-sealing of ducts and explosion risks; · the removal of standard sizes of rectangular ducts; · the omission of cleated joints; · the acceptance of proprietary flanges certificated to DW/TM I no longer illustrated in detail; · the consolidation into the document of coverage of hangers and supports; · the addition of a note on linings, along with their cleaning considerations; · the consolidated graphical representation of Class A, B and C air leakage characteristics, mandatory testing Class C only; · updated appendices on galvanising after manufacture, stainless steel, pre-coated steel, aluminium, Eurovent and galvanised material, plus a bibliography; · transport, handling, storage and interface with DW/TM2 Guide to Good Practice ­ Internal Cleanliness of New Ductwork Installations; · an overview of fire-rated ductwork; · a new appendix on inspection, servicing and cleaning access openings (the default inclusion of Level 1 should be noted); · a new section on standard component drawings - incorporating a framework of nomenclature, and a description of drawing symbols, abbreviations and rules - which is intended to reduce ambiguity and promote common understanding; · a rewritten description of all forms of dampers, for which I am indebted to Bill Clark and John Mawdsley of the HEVAC Association. I take this opportunity to acknowledge the permission granted by the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) of the USA for the use of its tie rod specification (designer approval required). And I also include a plea on behalf of ductwork constructors to be allowed to make the final choice of components and techniques within the parameters set by the designer, and allowed within this specification to satisfy performance characteristics. It will, of course, be clear to anyone who has ever taken on such a task that the production of this specification has involved a colossal input in terms of industry consultation and from a wide variety of individuals, a number of whom I should like to identify for special mention. They are: former Technical Sub-Committee members Keith Waldron and the late Keith Angood; current members Chris Collins, Stuart Howard, Brian James and - last but by no means least - Jim Murray; technical consultant Keith Elphick; and Ductwork Group secretary Gareth Keller. Finally, may I remind readers of the crucial importance of ensuring that all ductwork is manufactured and installed in a manner which is safe, efficient, effective and free of risk. The publication of DW/144 is intended to assist significantly in the achievement of this objective.

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Acknowledgements The HVCA wishes to record its sincere thanks to the following members - past and present - of the Technical Sub-Committee of the Ductwork Group, who contributed their time, knowledge and experience to the production of this document Edgar Poppleton (chairman) Keith Angood Chris Collins Stuart Howard Brian James Jim Murray Keith Waldron Technical Consultant: Keith Elphick Ductwork Group Secretary: Gareth Keller

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Contents

Page Notes 10 16.4 Fastenings 16.5 Stiffening 17. Construction (Straight Seamed) 18. Fittings 18.1 General Construction Requirements 18.2 Standardisation of fittings Part Six - Hangers and Supports 19. General Part Seven - General 20. Access/Inspection Openings 21. Regulating Dampers 22. Fire Dampers 23. Smoke Dampers 24. Combination Smoke and Fire Dampers 25. Flexible Ducts 26. Flexible Joint/Connections 27. Protective Finishes 28. Connections to Building Openings 29. Internal Duct Linings 30. Thermal Insulation 31. Kitchen Ventilation 32. Fire Rated Ductwork 33. Standard Component Drawings and Abbreviations Part Eight - Appendices Appendix A. Air Leakage from Ductwork Appendix B. Identification of Ductwork Appendix C. Guidance Notes for the Transport, Handling and Storage of Ductwork Appendix D. Ductwork Systems and Fire Hazards Appendix E. Hot Dip Galvanizing after Manufacture Appendix F. Stainless Steel for Ductwork Appendix G. Pre-Coated Steel Appendix H. Aluminium Ductwork Appendix J. Eurovent Appendix K. Summary of BS.EN10142: 1991 Continuously Hot-Dip Zinc Coated Mild Steel Strip and Sheet for Cold Forming Appendix L. `Design Notes for Ductwork' (CIBSE Technical Memorandum No. 8) Appendix M. Guidance Notes For Inspection, Servicing and Cleaning Access Openings Appendix N. Bibliography Appendix P. Conversion Tables 35 35 35 35 35 35 43 47 48 49 50 51 51 52 53 53 54 54 54 54 54

Part One - Technical Information to be provided by the designer 1. Introduction 11 2. Standards 11 3. Components 11 4. Particular Requirements 11 Part Two - Standards 5. Application 6. Ductwork Classification and Air Leakage 7. Materials 8. Ductwork Construction and Joint Sealing Part Three - Rectangular Ducts 9. Rectangular Duct Sizes 10. Construction 10.1 General 10.2 Steel Thicknesses 10.3 Longitudinal Seams 10.4 Cross Joints 10.5 Stiffeners 10.6 Ductwork Galvanised After Manufacture 10.7 Fastenings 11. Fittings 11.1 Standardisation of Fittings 11.2 Stiffeners 11.3 Splitters 11.4 Turning Vanes 11.5 Branches 11.6 Change Shapes 11.7 Expansions and Contractions 11.8 Sealant Part Four - Circular Ducts 12. Standard Sizes 13. Construction 13.1 Longitudinal Seams 13.2 Cross Joints 13.3 Fastenings 14. Fittings 14.1 Standardisation of Fittings 14.2 Nominal Diameters 14.3 Sheet Thickness 14.4 Sealing of Joints Part Five - Flat Oval Ducts 15. Standard Sizes and Sheet Thicknesses 16. Construction (Spirally wound) 16.1 General 16.2 Longitudinal Seams 16.3 Cross Joints 13 13 13 14 15 15 15 15 15 15 15 16 16 16 16 16 16 16 16 16 17 17 27 27 27 27 27 29 29 29 29 29 35 35 35 35 35

75 80 82 83 85 86 89 90 91

92 93 94 95 97

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List of Tables Table Part Two - Standards 1. Ductwork Classification and Air Leakage Limits 2. 3. 4. 5. Part Three - Rectangular Ducts Constructional Requirements Low Pressure up to 500Pa Constructional Requirements Medium Pressure up to 1000Pa Constructional Requirements High Pressure up to 2000Pa Fastening Centres Page

13-17 18-24 25-28 29 30 31 32-38 39-45 53-58 59-63 64-75

Socket and spigot cross joints Stiffeners Tie rod assembly Hard and Easy bends Turning Vanes Part Four - Circular Ducts Spiral and straight seams Cross joints spirally wound ducts Cross joints straight seamed ducts Part Five - Flat Oval Ducts Cross joints spirally wound ducts Cross joints straight seamed ducts Part Six - Hangers and Supports Horizontal ducts bearers and hangers Vertical ducts supports

22 23 24 25 25 29 30-31 32-33 39-40 41-42

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18 19 19 24 27 28 28 29 29 36 37 38 40

Part Four - Circular Ducts 6. Standard Sizes 7. Spirally-Wound Ducts 8. Straight-Seamed Ducts 9. Permitted fastenings and maximum spacings 10. Fittings Sheet Thicknesses Part Five - Flat Oval Ducts 11. Standard sizes and sheet thicknesses 12. Stiffening requirements low and medium pressures 13. Stiffening requirements high pressure 14. Permitted fastenings and maximum spacings Part Six - Hangers and Supports 15. Supports for horizontal ducts - rectangular, flat oval and circular Part Seven - General 16. Standard Abbreviations Part Eight - Appendices 17. Air Leakage Rates 18. Recommended duct identification colours 19. Examples of further identification symbols 20. Ductwork galvanized after manufacture rectangular 21. Compositions of the commonly used Stainless Steel grades 22. Rectangular aluminium ducts low pressure constructional requirements 23. Circular aluminium ducts low pressure constructional requirements 24. Zinc coating mass (weight) 25. Access requirements for inspection, servicing and cleaning List of Illustrations Figs 1-8 9 10-12 Part Three - Rectangular Ducts Longitudinal Seams Illustrations of panel stiffening Flanged cross joints

76-77 78-79 80 81-124

45-46 46 50 52 55-61 62-67 68-70 71

Part Seven - General Fire barrier/Fire damper expansion Flexible joint connections Standard component drawings Rectangular 125-152 Standard component drawings Circular 153-167 Standard component drawings Flat Oval 168-177 Plant/equipment/miscellaneous 178 Part Eight - Appendices Permitted leakage at various pressures Example of duct identification symbol

44 72-73 76 80 81 85 88 90 91 93 94 Pages 20 20 21 9

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Notes In this document: (1) Even where a ductwork job specification calls for the system to be wholly in accordance with DW/144, it will still be necessary for the designer, in addition to providing drawings showing details and dimensions of the ductwork, to identify specific requirements, particular to his or her design. The technical information to be provided by the designer is therefore set out in detail on page 11. (2) All dimensions quoted in this specification refer to the nominal sizes, which are subject to the normal relevant commercial and published tolerances. (3) Manufacturing techniques are continually subject to change and improvements and in respect of proprietary methods and devices this specification does not preclude their use if they can be demonstrated to the designer to be equally satisfactory. Where there is divergence between the requirements of DW/144 and the manufacturer's recommendations for proprietary methods and devices, the latter shall take precedence. (4) The expressions `low-pressure,' 'medium-pressure' and 'highpressure' relate to the pressure/velocity classes set out in Table 1. (5) `Mean air velocity' means the design volume flow rate related to the cross-sectional area. (6) Reference to the air distribution system pressure relate to the static pressure of the relevant part of the ductwork system and not to the fan static pressure. (7) The symbol for litres is `L': 1000 litres per second is equivalent to 1 cubic metre per second. (8) The pascal (Pa) is the internationally agreed unit of pressure. The relationship of the pascal to other units of pressure is: 500 pascals = 500 Newtons per square metre = 5 millibars = approximately 2 inches water gauge.

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Part One - Technical information to be provided by the designer to the ductwork contractor

1 INTRODUCTION The selection of constructional methods is the decision of the Manufacturer to conform with the performance requirements of the specified ductwork classification. Sections 2-4 below define the information that is to be provided by the Designer. 2 STANDARDS 2.1 Pressure classification (Table 1) 2.2 Leakage classification (Table 1) 2.3 Positive and Negative pressures (Table 1) 2.4 Materials (Section 7) 2.5 Any special system requirements 3 COMPONENTS 3.1 Inspection/servicing access openings (Section 20 and Appendix M) Number and location of all panels and covers for inspection and/or servicing access other than those covered in Section 20 and summarised as Level 1 requirements in table 25 of Appendix M. Number and location of test holes, instrument connections and hinged doors as defined in Section 20. 3.2 Cleaning access (Section 20.8 and Appendix M) Designers shall stipulate their requirements for periodic internal cleaning of ductwork and for the consequent need for adequate access for specialist cleaning equipment. 3.3 Regulating dampers (Section 21) Specification, location and mode of operation of all regulating dampers. 3.4 Fire dampers (Section 22) Specification and location of all fire dampers to meet the requirements of the Authority directly concerned with fire protection. 3.5 Smoke dampers (Section 23)/Combination smoke and fire dampers (Section 24) Specification and location of all smoke dampers to meet the requirements of the Authority directly concerned with fire protection. 3.6 Flexible ducts (Section 25) Specification and location of any flexible ductwork. 3.7 Flexible joint connections (Section 26) Specification and location of any flexible connections eg. plant or building expansion joints. 4. PARTICULAR REQUIREMENTS 4.1 Air leakage testing (Section 6 and Appendix A) The extent of any air leakage testing. While it shall be mandatory for high-pressure ductwork (as defined in this specification) to be tested for air leakage in accordance with the procedure set out in DW/143, A practical guide to Ductwork Leakage Testing, no such testing of low- or medium-pressure ductwork is required. 4.2 Protective finishes (Section 27) Details and specification of any protective finishes. 4.3 Fire rated and smoke extract ductwork (Appendix D) The extent and limits of protection for any fire resisting ductwork. 4.4 Internal thermal/acoustic lining (Section 29) The extent of any ductwork requiring internal acoustic/thermal lining is to be clearly identified. A detailed specification of materials and method of application is required. The practical aspects of cleaning or maintenance must be addressed by the designer before deciding to internally line ductwork. 4.5 External thermal/acoustic insulation (Section 30) The extent and thickness of insulation to be provided by others should be stated. 4.6 Special supports (Section 19) Details of any spanning steel or special support requirements not covered by Section 19 4.7 Attachment to building structure (Section 28) Specific requirements for the junction of ductwork and associated components to openings should be detailed and specified and the limits of responsibility defined. The provision of penetrations and associated framings are outside the scope of this specification. 4.8 Air terminal units Detail and specifications of all Air Terminal Units. It is expected that all Air Terminal Units and their Plenums (See Figures 120 to 124) will be supported by the Ceiling Grids unless the designer indicates an independent method of support. 4.9 Ductwork layout drawings Details of any special requirements relating to CAD, scales, etc. It is common practice and cost effective for ductwork manufacturers to utilise their approved ductwork layout drawings as a basis of their manufacturing/installation information by adding the necessary details to the same drawing. Scales of 1:50 or smaller may preclude this practice, therefore, larger scales might be more appropriate. The final choice of manufacturing/installation scales shall be left to the ductwork contractor. 4.10 Other requirements Details of any requirements for the ductwork not in accordance with the provisions of this specification, including any modified construction required to conform with any requirements concerning external ductwork (See 5.3) or to meet the regulations of a local authority or other controlling body.

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4.11 Reference to the designer In consideration of the foregoing, reference is also made to the designer in the following clauses: Clause 5.3 7.4, 7.5, 7.6 10.5.2 11.1 14.1 16.3.1 19.1, 19.4 19.6, 19.7 20.1, 20.1.1.1, 20.6, 20.8 20.9 21.1, 21.3.1 21.3.4 22.3, 22.7 24.3 25.1 26.1 27,27.3.4 29.1, 29.4, 30.2, 30.3, 33.2 Fig. 176 Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F Appendix L Appendix M Page 13 14 16 16 29 35 43 44 47 48 48 49 50 51 51 52 53 54 71 75-79 80,81 82 83,84 85 86-88 93 94

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Part Two - Standards

5 APPLICATION 5.1 This specification sets out minimum requirements for the manufacture and installation of ductwork for commercial and industrial air distribution systems, made from any of the materials listed in Section 7 and being within the limits of size and/or metal thicknesses specified in the relevant tables. Normal operating temperatures are assumed within the pressure/velocity limits and the limits of air leakage for the various pressure classes prescribed in Table 1. 5.2 This specification is not intended to apply to ductwork handling air which is polluted or is otherwise exceptional in respect of temperature or humidity (including saturated air); nor is it suitable for ductwork exposed to a hostile environment, e.g. contaminated air, off-shore oil rigs, etc. The design, construction, installation, supports and finishes in such cases should be given special consideration in relation to the circumstances of each case. 5.3 This specification is not suitable for ductwork exposed to external atmosphere and the Designer will need to give specific details of any special finishes/construction (See Section 27). 6 DUCTWORK CLASSIFICATION AND AIR LEAKAGE 6.1 Classification and air leakage limits Ductwork classification and air leakage limits are set out in Table 1. 6.2 Compatibility with CEN The leakage factors used in Table 1 for Classes A, B and C are the same as those for the classes similarly designated in the CEN Document Pr EN 12237/Pr EN 1507. 6.3 Leakage at various pressures; and other relationships Applying the limits specified in Table 1, Appendix A (Table 17) sets out the permitted leakage at each of a series of pressures up to a maximum for each class. Included in that appendix is a graphical presentation of the pressure/leakage relationship. DW/143 A practical guide to Ductwork Leakage Testing, also gives details of the basis for the leakage limits specified in Table 1. 6.4 Air leakage testing Air leakage testing of low and medium pressure ductwork is not mandatory under this specification. Air leakage testing of high pressure ductwork is mandatory under the specification and for details of testing procedure refer to DW/143 A practical guide to Ductwork Leakage Testing. 7 MATERIALS 7.1 Application This specification applies to ductwork constructed from materials as defined below, or equal. Minimum steel thickness is to be taken as a nominal thickness within the tolerances to BS.EN10143:1993. (See Appendix K) 7.2 Zinc-coated steel Ductwork will normally be constructed from hotdip galvanized steel to BS.EN10142:1991, Grade DX51 D+Z, coating type Z275.

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7.3 Mild steel Where mild steel is specified, it shall be cold-reduced steel to BS.EN10130:1991, Grade FEP 01A. 7.4 Stainless steel Where stainless steel is specified. it will be the responsibility of the designer to indicate the type most suitable for the conditions to which the ductwork will be exposed. In doing so, it is recommended that the factors set out in Appendix F should be taken into account. In this connection, reference must be made to BS 1449: Part 2, which includes stainless steel. 7.5 Pre-coated steel Pre-coated steel may be specified for aesthetic or other reasons. The designer must then consider the availability of suitable materials and the restriction on fabrication methods. Guidance notes are available in Appendix G. 7.6 Aluminium Where aluminium is specified, it will be the responsibility of the designer to define the type most suitable for the conditions to which the ductwork will be exposed. Reference must be made to BS.EN485, BS.EN515 and BS.EN573 for aluminium sheet and BS.EN755 Parts 3-6 for aluminium section. (Constructional requirements for ductwork made from aluminium sheet and general notes on the material are set out in Appendix H.) 8 DUCTWORK CONSTRUCTION AND JOINT SEALING 8.1 Ductwork construction The selection of longitudinal, cross joint and stiffener types within the criteria laid down in the tables should be the responsibility of the manufacturer. 8.2 Joint sealing and sealants 8.2.1 General The integrity of the ductwork depends on the successful application of the correct sealant, gaskets or tape. The materials used should be suitable for the purpose intended and satisfy the specified pressure classification. Illustrations indicating sealant locations will be found in the following sections dealing with the construction of rectangular, circular and flat oval duct sections. IN ALL CASES, SEALANT MATERIALS MUST BE APPLIED STRICTLY IN ACCORDANCE WITH THE MANUFACTURER'S INSTRUCTIONS AND COSHH ASSESSMENT.

8.2.2 Liquid and mastic sealants These are typically applied to a longitudinal seam formed between two sheets of metal, a socket and spigot, cleated or flanged cross joints. Particular care is needed when sealing of "corner pieces" on the proprietary 'slide-on' type flange and reference should be made to the manufacturer's assembly and sealing instructions. 8.2.3 Gaskets These can be of various materials in the form of a preformed roll, sheet or strip, applied between opposing faces of flanged cross joints. In the case of proprietary 'slide-on' type flanges, it is advisable to use the gasket strip recommended by the manufacturer. Factory-fitted proprietary synthetic rubber '0'ring type gaskets are also acceptable for socket and spigot joints on circular duct systems. 8.2.4 Tapes 8.2.4.1 The application of tapes - Best suited, but not limited, to cross joints on circular or flat oval ductwork. Where chemical reaction tape, heat shrinkable tape or other approved material is used on flat oval ductwork care should be taken to maintain close contact between the material and the flat sides of the duct until the joint is completed. 8.2.4.2 Chemical reaction tape - An impregnated woven fibre tape and a resin type activator/adhesive. On application of the activator/adhesive the tape becomes pliable and can then be applied to any surface shape. The liquid reacts with the tape, causing the 2part system to `set'. 8.2.4.3 Heat shrinkable band/tape - A thermoplastic material, coated on the inside with hot metal adhesive. The band (or an appropriate length of tape) is cut from the roll and wrapped around the joint. When heated the tape shrinks tightly around the joint thus providing a seal. 8.2.4.4 Self adhesive tape - Manufactured from various materials including cloth based, PVC and aluminium foil. Typically applied externally to socket and spigot cross joints. However, it is difficult to provide the dry, dust and grease free surface that is required for a successful application and this method is therefore not recommended as a primary source of sealant. NB! Risk of explosions Where ductwork is blanked off prior to leakage testing or to prevent the ingress of contamination, care should be taken to ensure that all joint sealing solvent vapours are dispersed from the ductwork systems.

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Part Three - Rectangular Ducts

9 RECTANGULAR DUCT SIZES This specification covers duct sizes up to a maximum longer side of 3,000 mm. Duct sizes with an aspect ratio greater than 4:1 are not recommended. Although they offer no problems of construction, they increase frictional resistance and the possibility of noise. 10 CONSTRUCTION 10.1 General The minimum constructional requirements for rectangular ductwork depend upon the pressure classification as set out in Tables 2 to 4. The ductwork construction and joint sealing standards are set out in section 8. 10.2 Steel thicknesses Minimum steel thicknesses related to duct longer side to pressure classification are given in Tables 2 to 4. 10.3 Longitudinal Seams Longitudinal seams are illustrated in Figs. 1 to 8. The limits of use, if any, are given with the individual illustrations. 10.3.1 Sealing of Longitudinal Seams Sealant will be applied using one of the following methods: a) As an edge sealant on the external seam surface. b) As an edge sealant on the internal seam surface. c) Internal to the joint seam itself. The most appropriate method will be determined by the manufacturer relative to their product and will be associated with either traditional fabrication/assembly methods, factory or site based, and/or proprietary methods. The ultimate proof of a seal is that the ductwork system meets the pressure classification specified. For details of sealant see section 8. 10.3.2 Welded seams A welded seam is acceptable without sealant, provided that the welding is continuous. 10.4 Cross joints 10.4.1 Cross joint ratings For cross joints, a system of rating has been used to define the limits of use. The rating for each cross joint is given with its drawing, and the limits applying to that rating, in terms of

duct size longer side and maximum spacing, are given in Tables 2 to 4. Other limits on use are given with the individual drawings. Note: Proprietary products used in the construction of cross joints should be approved by an independent test house following tests defined in DW/TM1 "Acceptance scheme for new products - Rectangular cross joint classification." Figures Nos 10 and 13 to 17 illustrate non proprietary joints that have an established rating. 10.4.2 Sealant in cross joints Sealant shall be used between sheet and section in all cross joint assemblies. (see section 8) With socket and spigot joints made on site, sealant shall be applied during or after assembly of the joint. It is permissible to use chemicalreaction tape or heat-shrink strip as alternative methods of sealing, provided that close contact is maintained over the whole perimeter of the joint until the joint is completed. With all flanged joints, the sealant between sheet and section should preferably be incorporated during construction at works, but site applied sealant is acceptable. The joint between sections of ductwork is then made, using approved type of sealant or gasket. With proprietary flanging systems particular attention should be paid to the sealing of corner pieces and flanges, reference should be made to the manufacturer's assembly and sealing instructions. 10.4.3 Adjustabletslip joints In order to accommodate manufacturing/building tolerances, site modifications etc, it is accepted practice to use an adjustable joint as illustrated in Fig. 14. 10.5 Stiffeners 10.5.1 External stiffeners The sections (including proprietary flanges) suitable for use as single stiffeners have been given a rating from S1 to S6 in terms of duct size longer side and maximum spacing. The ratings are specified with the illustrations of the stiffeners, Figs. 18 to 23, and the limits of use are given in Tables 2 to 4. The stiffeners for socket and spigot joints covered in Figs. 15, 16 and 17 are also applicable to stiffeners in general.

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10.5.2 Internal stiffeners Tie bars connecting the flanges of cross joints illustrated in Figs 11 and 12, are the only form of internal stiffening for rectangular ductwork recognised by this specification and reference should be made to HVCA publication DW/TM 1. Alternative methods for the attachment of tie bars are shown in Figs. 25 to 28. The use of tie bars or other forms of internal stiffening or bracing shall be acceptable if proved to the designer to be equally satisfactory. SMACNA (Sheet Metal and Air Conditioning Contractors' National Association), which is the American equivalent to the HVCA Ductwork Group, have produced an Addendum No. l (November 1997) to their publication "HVAC Duct Construction Standards, Second Edition - 1995". The addendum contains the extensive technical information and data on the subject of mid panel tie rods and SMACNA have given their kind permission for this specification to make reference to this fact. Designers and manufacturers who wish to incorporate this form of internal stiffening into a ductwork system should contact SMACNA direct to obtain copies of their publications (See Appendix N, Bibliography). 10.6 Ductwork galvanized after manufacture Appendix E sets out the recommended sheet thicknesses and stiffening for ductwork galvanized after manufacture. 10.7 Fastenings 10.7.1 Permitted types and maximum centres Table 5 sets out the permitted fastenings and the maximum spacings for all ductwork classifications. All duct penetrations shall be sealed. 10.7.2 Rivets Manufacturers' recommendations as to use, size and drill size are to be followed. Rivets resulting in an unsealed aperture shall not be used. 10.7.3 Set screws, nuts and lock bolts Materials shall be of mild steel, protected by electrogalvanizing, sherardizing, zinc-plating, or other equal and approved corrosion resistant finish. 10.7.4 Self tapping and piercing screws Providing an adequate seal can be achieved, and the protrusions into the ductwork are unlikely to cause injury, then self-tapping or piercing screws may be used. 10.7.5 Welding of sheet The suitability of welding for sheet-to-sheet fastening will be governed by the sheet thickness, the size and shape of the duct or fitting and the need to ensure airtighteness. Welded joints shall provide a smooth internal surface and shall be free from porosity. Distortion shall be kept to 16

a minimum. Areas where the galvanizing has been damaged or destroyed by welding or brazing shall be suitably prepared and painted internally and externally with zinc-rich or aluminium paint as defined in Section 27.3.2. 11 FITTINGS 11.1 Standardisation of fittings The terminology and descriptions of rectangular duct fittings as set out in Section 33 are recommended for adoption as standard practice to provide common terms of reference for designers, quantity surveyors and ductwork contractors, and of those using computers in ductwork design and fabrication. Bends are designated as `hard' or `easy', and these terms as used herein have the following meanings: `Hard' signifies rotation in the plane of the longer side of the cross section. `Easy' signifies rotation in the plane of the shorter side of the cross section. An example illustrating these terms is given in Fig. 29. 11.2 Stiffeners The flat sides of fittings shall be stiffened in accordance with the construction Tables 2 to 4. On the flat sides of bends, stiffeners shall be arranged in a radial pattern, with the spacing measured along the centre of the bend. 11.3 Splitters If the leading edge of the splitters exceeds 1250 mm fit central tie bars at both ends to support the splitters. Leading and trailing edges of splitters must be edge folded and flattened and be parallel to the duct axis. Splitters shall be attached to the duct by bolts or mechanically-closed rivets at 100 mm maximum spacing (or by such other fixing as can be shown to be equally satisfactory e.g proprietary sealed splitter pins). 11.4 Turning vanes Where specified, or shown on drawings, square throat bends with either duct dimension greater than 200 mm shall be fitted with turning vanes which are illustrated in Figures 30a and 30b. Turning vanes at 60 mm maximum centres shall be fixed at both ends either to the duct or compatible mounting tracks in accordance with manufacturer's instructions, the whole bank being fixed inside the duct with bolts or mechanically closed rivets at 150 mm maximum spacing. The maximum length of turning vane between duct walls or intermediate support shall be 615 mm for single skin vanes and 1250 mm for double skin vanes. Typical examples of fitting turning vanes when the maximum permitted vane lengths are exceeded are shown in Fig. 30c.

11.5 Branches When fitting branch ducts to a main duct, care should be taken to ensure that the rigidity of the duct panel is maintained in terms of the stiffening criteria. 11.6 Change shapes Where a change shape is necessary to accommodate the duct and the cross-sectional area is to be maintained, the slope shall not exceed 22½° on any side (See Figs 99 to 103). Where a change in shape includes a local reduction in duct crosssectional area, the slope should not exceed 15° on any side and the reduction in area should not exceed 20 per cent.

11.7 Expansions and contractions Where these are required, an expansion shall be made upstream of a branch connection and a contraction downstream of a branch connection. The slope of either an expansion or a contraction should not exceed 22½° on any side. Where this angle is not practicable, the slope may be increased, providing that splitters are positioned to bisect the angle between any side and the centre line of the duct (See Figs 99 to 101). 11.8 Sealant Sealant shall be used in all longitudinal seams and cross joints of fittings. Sealant shall be to the options listed in Section 8.

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Notes (applicable to Tables 2 to 4) (1) The joints and stiffeners have been rated in terms of duct longer side and maximum spacing - see 10.4 for joints and 10.5 for stiffeners. (2) In Col. 3: `PS' = plain sheet `SS' = stiffened sheet, by means of (a) beading at 400 mm maximum centres: or (b) cross-breaking within the frame formed by joints and/or stiffeners: or (c) pleating at 150 mm maximum centres. (3) Stiffened panels may limit the choice of insulation materials. (4) For ductwork galvanized after manufacture, see 10.6 and Appendix E. (5) For aluminium ductwork, see Appendix H. (6) For constructional constraints of stainless steel ductwork see Appendix F. (7) Although not covered in this specification, due to their relatively infrequent use, cleated cross joints are an accepted constructional practice and the HVCA Ductwork Group should be contacted if details of their ratings and limitations are required. (8) Intermediate stiffeners using rolled sheet angle profiles, illustrated in Figs. 19 to 23 of the appropriate rating may also be utilised ensuring that rigid corners are achieved.

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NOTE: The above illustrations are typical examples of cross joint profiles that are in common use for connecting rectangular sheet metal ducts. There are no set dimensions for these profiles shown in Figs. 1 1 and 12 provided they are certified under the HVCA testing scheme DW/TM1 "Acceptance Scheme for new products - Rectangular cross joint classification" and are appropriate to the duct application. The manufacturer's technical data should be followed with respect to: Connections to duct wall Corner treatment Addition of cleats Application of sealants Strength ratings Application of tie bars A list of manufacturers and profiles that are covered by current DW/TMI certificate is available from the Ductwork Group Secretary at HVCA.

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(1) A minimum of 2 fixings per side, with a maximum distance from the corner to the first fixing of 50 mm (2) Except when pierced dimpling is used, one of the other types of fastening must be used at each end in addition to dimpling (3) In addition to dimpling, one of the other types of fastening must be used at 450 mm centres, and in all cases not less than 1 per side (4) Where manufacturers have specific recommendations, then these shall take precedence over the centres in the Table above (5) Mechanically closed rivets are not recommended for fixing external stiffeners to ductwork exceeding 500pa negative. 24

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Part Four - Circular Ducts

and contractors in the meantime are invited to evaluate them based on information currently available. 13.1 Longitudinal seams 13.1.1 Spirally-wound ducts The seam used in spirally-wound circular ducts, provided it is tightly formed to produce a rigid duct, is accepted as airtight to the requirements of all the pressure classifications covered in this specification, without sealant in the seam. 13.1.2 Straight-seamed ducts The longitudinal seam for straight-seamed circular ducts shall be either the grooved seam continued to the extreme end of the duct and sealed, or a continuous butt lap weld or spot/stitch weld and sealed lap joint (at 30 mm centres) provided this gives a smooth internal finish (see Fig. 31). 13.2 Cross joints 13.2.1 General Cross joints for circular ducts, both spirallywound and straight-seamed, are illustrated in Figs.32 to 45. They include several proprietary types and the limits of use in terms of diameter and pressure classes are noted against each. 13.2.2 Sealant All circular cross joints shall be sealed. (see section 8) The use of chemical-reaction tape or heatshrinkable band shall be regarded as an effective sealant in respect of the socket and spigot joints illustrated. 13.2.3 Welded joints The limitations for welded joints are given in 13.3.5. 13.3 Fastenings 13.3.1 Permitted types and maximum centres Table 9 sets out the permitted fastenings and maximum spacings for low-, medium- and highpressure ducts. All duct penetrations shall be sealed. 13.3.2 Rivets Manufacturers' recommendations as to use, size and drill size are to be followed. Rivets resulting in an unsealed aperature shall not be used. 13.3.3 Set screws, nuts and lock bolts Materials shall be of mild steel, protected by electrogalvanizing, sherardizing, zinc plating or other equal and approved finish. 13.3.4 Self tapping and piercing screws Providing an adequate seal can be achieved, and the protrusions into the ductwork are unlikely to cause injury, then self-tapping or piercing screws may be used.

13 CONSTRUCTION Spirally-wound ducts and straight seamed ducts The minimum constructional requirements set out in Table 7 and 8 are common to the full range of pressures covered in this specification. The ductwork construction and joint sealing standards are set out in section 8. Spirally wound duct with thinner than traditional wall thickness and with one or more corrugations (ribs) formed between the lock seams are now available. As design and installation experience with these are gained and more functional performance criteria are identified it is anticipated that such forms may be added to later updates. Designers

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13.3.5 Welding of sheet The suitability of continuous welding or spot welding for sheet to sheet fastening will be governed by the sheet thickness, the size and shape of the duct or fitting and the need to ensure airtightness. Welded joints shall provide a smooth

internal surface and shall be free from porosity. Distortion shall be kept to a minimum. Areas where the galvanizing has been damaged or destroyed by welding or brazing shall be suitably prepared and painted internally and externally with zinc-rich or aluminium paint.

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14 FITTINGS 14.1 Standardisation of fittings The terminology and descriptions of circular duct fittings as set out in Section 33 are recommended for adoption as standard practice, to provide common terms of reference for designers, quantity surveyors and ductwork contractors, and those using computers in ductwork design and fabrication. The requirements for circular duct fittings apply throughout the pressure ranges covered in this specification. 14.2 Nominal diameters The nominal diameter (see Table 6) is the size used for design and ordering. With socket and spigot joints, care should be taken to ensure that the dimensions of the ducts and fittings are correctly related, so that the joint can be effectively sealed. 14.3 Sheet thickness Sheet thickness for circular duct fittings (determined by the largest diameter) shall be not less than those quoted in Table 10. 14.4 Sealing of joints Sealant shall be used in all cross joints and fittings. Such sealant shall be in accordance with the requirements of Section 8.

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31

32

33

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Part Five - Flat Oval Ducts

15 STANDARD SIZES AND SHEET THICKNESSES 15.1 Table 11 sets out the standard sizes of spirallywound oval ducts offered by the manufacturers of ducts of this section. 16 CONSTRUCTION (SPIRALLY-WOUND DUCTS) 16.1 General `Flat oval' is the term used to describe a duct of crosssection with flat opposed sides and semicircular ends. The duct is formed from a spirallywound circular duct, using a special former. Apart from stiffening (see Tables 12 and 13), flat oval ducts have the same constructional requirements throughout the pressure ranges covered in this specification. The ductwork construction and joint sealing standards are set out in Section 8. 16.2 Longitudinal seams Spirally-wound flat oval duct is accepted as airtight to the requirements of this specification without sealant in the seams, provided the grooved seam is tightly formed to produce a rigid duct. 16.3 Cross joints 16.3.1 General Cross joints shall be as Figs. 53 to 58 inclusive or such other joint as can be demonstrated to the designer to be equally satisfactory. 16.3.2 Sealant All flat oval cross joints shall be sealed. (See Standards Section 8). 16.3.3 Welded joints The limitations for welded joints are given in 16.4.5. 16.4 Fastenings 16.4.1 Permitted types and maximum centres Table 14 sets out the permitted fastenings and maximum spacings for low-, medium- and highpressure ducts. All duct penetrations shall be sealed. 16.4.2 Rivets Manufacturers' recommendations as to use, size and drill size are to be followed. Rivets resulting in an unsealed aperature shall not be used. 16.4.3 Set screws, nuts and lock bolts Set screws and nuts shall be of mild steel, protected by electro-galvanizing, sherardizing, zinc plating or other equal and approved finish. 16.4.4 Self tapping and piercing screws Providing an adequate seal can be achieved, and the protrusions into the ductwork are unlikely to cause injury, then self-tapping or piercing screws may be used. 16.4.5 Welding of sheet The suitability of continuous welding or spot welding for sheet to sheet fastening will be governed by the sheet thickness, the size and shape of the duct or fitting and the need to ensure air-tightness. Welded joints shall provide a smooth internal surface and shall be free from porosity. Distortion shall be kept to a minimum. Areas where the galvanizing has been damaged or destroyed by welding or brazing shall be suitably prepared and painted internally and externally with zinc-rich or aluminium paint. 16.5 Stiffening The larger sizes of flat oval duct are stiffened by swages, as indicated in Table 11. Additionally, tie rods (see Figs. 25 to 28) are required, positioned as indicated in the respective tables and illustrations. In special situations as an alternative to tie rods, stiffening in the form of external angles may be used to meet the requirements of the corresponding rectangular duct sizes. 17 CONSTRUCTION (STRAIGHT-SEAMED) Flat oval ducts with opposed sides and semi-circular ends may also be formed using plain sheet and straight seams. Ducts so formed should follow the metal thicknesses and stiffening requirements specified for the corresponding sizes of rectangular ducts, except that stiffening is necessary on the flat sides only. Seams and cross joints (see Figs 59 to 63) shall be sealed to ensure the necessary degree of airtight-ness throughout the pressure ranges covered in this specification.

18 FITTINGS 18.1 General constructional requirements Sheet thicknesses for flat oval fittings (determined by the periphery of the larger end) shall be not less than those given in Table 11 for the ducts themselves. With socket and spigot joints, care should be taken to ensure that the dimensions of ducts and fittings are correctly related. All the seams and joints integral to a fitting shall be sealed to the same standard as the duct. (See Section 8). 18.2 Standardisation of fittings The terminology and descriptions of flat oval duct fittings as set out in Section 33 are recommended for adoption as standard practice, to provide common terms of reference for designers, quantity surveyors and ductwork contractors, and those using computers in ductwork design and fabrication. The requirements for flat oval duct fittings apply throughout the pressure ranges covered in this

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Part Six - Hangers and Supports

19 GENERAL 19.1 Principles adopted Supports are an essential part of the ductwork system, and their supply and installation are normally the responsibility of the ductwork contractor. The choice between the available methods of fixing will depend on the type of building structure and on any limitations imposed by the structural design. Further, unless the designer has specified his requirements in detail, the load to be carried shall be understood to be limited to the ductwork and its associated thermal and/or acoustic insulation. It is not practicable to deal here with the full range of supports available, which increasingly includes proprietary types, so in this section various methods of support are dealt with in principle under the three elements of: (1) the attachment to the structure; (2) the hanger itself; and (3) the duct bearing member with illustrations of those most commonly used. Supports for ductwork external to the building have been excluded, as these are individually designed to suit the circumstances, and also may be required to meet local authority standards. For the same reasons, floor supports have not been dealt with. With a proprietary device, it will, unless the designer has specified his requirements in detail, be the responsibility of the ductwork installer to ensure that it meets requirements, with a sufficient margin of overload; and that it is installed in accordance with the manufacturer's recommendations. The absence of any method or device from this specification does not preclude its use if it can be demonstrated that it is suitable for the duty assigned to it, with a sufficient margin of safety against overload; and this will be the responsibility of the ductwork installer, unless the designer has specified his requirements in detail. 19.2 Fixing to building structure The fixing to the building structure should be of a strength and durability compatible with those of the ductwork support attached to it. A fixing to concrete or brickwork must be made in such a way that it cannot loosen or pull out through normal stressing or through normal changes in the building structure. 19.3 Horizontal ductwork 19.3.1 The hanger itself The hanger itself is usually mild steel plain rod or studding or flat strap, pre-treated by, e.g. hotdip galvanizing, sherardizing, electro-deposited zinc plating or by other accepted anti-corrosion treatment. Other materials, such as stranded wire, may also be acceptable. Projection of a rod or studding hanger through the bottom bearer should, where practicable, not exceed twice the thickness of the securing nut. Provided the integrity of the ductwork is maintained, hangers may be attached to the corners of the flanges as an alternative to the use of a bottom bearer. With proprietary devices manufacturers' recommendations for use should be followed. 19.3.2 The duct bearing member The choice of the lower support will be dictated by the actual duct section. 19.3.3.1 Rectangular ducts Table 15 gives minimum dimensions for the hangers and for angle, channel and profile sections. The angle is shown in Fig. 73, the profile channel sections in Figs. 74 and 75. Typical arrangements of bottom bearer supports for plain, and insulated ducts are shown in Figs. 68, 69 and 70. 19.3.3.2 Circular ducts Table 15 gives minimum dimensions for the hanger and for the brackets - as illustrated in Figs. 64 to 67. 19.3.3.3 Flat oval ducts Table 15 gives minimum dimensions for the hanger; and for the bearer, depending on whether the flat side of the duct is horizontal or vertical. Typical arrangements for flat oval duct supports are shown in Figs. 68, 71 and 72. 19.4 Vertical ducts The design of supports for vertical ducts is dictated by site conditions, and they are often located to coincide with the individual floor slabs, but if the spacing exceeds 4 metres the designer must specify his requirements. Vertical ducts should be supported from the stiffening angle or the angle frame, or by separate supporting angles fixed to the duct. A typical method of supporting vertical rectangular ducts is shown in Fig. 76 and for circular ducts in

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Fig. 77. The same methods are applicable to vertical flat oval ducts. 19.5 Heavy loadings For ducts larger than those covered by Table 15, or where heavy equipment, mechanical services, ceilings or other additional load is to be applied to the ductwork, supports shall be designed to suit the applications. 19.6 Insulated ducts with vapour sealing Where the temperature of the air within the duct is at any time low enough to promote condensation on the exterior surface of the duct and cause moisture penetration through the thermal insulation, vapour sealing may be called for, and in this case the most important requirement is to limit penetration of the seal.

The extent of any vapour sealing of ductwork thermal insulation and the method to be used, must be clearly specified in advance by the designer. 19.7 Heat transfer It is not normally necessary to make special arrangements for the limitation of heat transfer via the duct supports. However, there may be special cases where the temperature difference justifies a heat barrier to conserve heat or to prevent condensation and such requirements must be specified by the designer. 19.8 Fire rated ductwork DW/144 supports cannot be used on fire rated ductwork systems. See Appendix D and in particular notes in D2.1 Method 3 and D.2.3.

Notes to Table 15 (1) The dimensions included in Table 15 are to be regarded as minima. (2) The maximum spacings set out in Table 15 are related solely to duct weight considerations. Closer spacings may be required by reason of the limitations of the building structure or to achieve the necessary duct rigidity. (3) Rolled steel channels may be used as bearing members provided they meet the design characteristics of the bearing members tabled above. (4) As an alternative to drop rod or studding, wire rope may be utilised to suit individual manufacturer's fixing methods and loading limitations. 44

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Part Seven - General

20 ACCESS/INSPECTION OPENINGS 20.1 General This section covers inspection/servicing access only. Appendix M sets out guidance notes, in summary form, of the access considerations that should be made by the designer in terms of inspection, servicing and cleaning access. All openings shall be made safe and have sealed panels/covers designed so that they can be speedily removed and refixed. Multiple set screws are not recommended, and self-piercing screws are not acceptable as a method of fixing. The services coordinator should ensure that there is an area free of services and other obstructions to enable a panel/cover to be removed. 20.1.1 Function 20.1.1.1 An access panel is to be provided adjacent to items of in-line equipment that require either regular servicing or intermittent access. The opening will be sized to provide hand and/or arm access only and the designer shall specify the size and location of panels where larger dimensions are required and in these cases the panels should not exceed 450 x 450 mm. 20.1.1.2 An inspection cover is to be provided adjacent to items of in-line equipment that need visual inspection only of internal elements from outside of the ductwork. The inspection opening should have a minimum size of 100 mm sq/dia. 20.2 Access panels 20.2.1 It shall be standard practice to provide access panels for the inspection and servicing of plant and equipment as follows: 20.2.1.1 Fire/Smoke dampers Panels to be located so as to give access both to the blades and fusible links. On multiple assembly units it may be necessary to provide more than one panel and this may be determined by both external access conditions and the internal reach to the blades and the fusible links. 20.2.1.2 Filters Panel to be located on the air entry side ie. upstream (Note: Dimensions of access may need to be changed to suit filter elements of the front withdrawal type.) 20.2.1.3 Heating/cooling coils and in-duct fans/devices Panel to be located on the air entry side ie. upstream 20.2.2 It shall be standard practice to connect safety restraints to access panels located in riser ducts. 20.2.3 Subject to the restrictions imposed by duct dimensions, openings for access shall satisfy the maintenance needs of the designated equipment with consideration being given, if more practicable, to the use of removable duct sections or flexible ducts/connections. 20.3 Inspection covers It shall be standard practice to provide inspection covers adjacent to regulating dampers where either the control linkage is mounted internally within the airstream or if a multi-bladed unit is an integral part of the ductwork run. It is not necessary to provide inspection covers adjacent to either single blade regulating dampers or flanged damper units. 20.4 Hand holes Hand holes to permit proper jointing of duct sections shall be provided at the manufacturer's discretion, but should be kept to a minimum and made as small as practicable. The hand hole cover shall be sealed and securely fastened. 20.5 Openings in insulated ducts It will be the responsibility of the insulation contractor to `dress' their insulation to the edge of the access opening without impeding the functionality of the panel, cover or door. 20.6 Test holes for plant system commissioning It shall be standard practice to provide test holes, normally 13 mm diameter and fitted with an effective removable seal, at the following locations: at fans (in the straightest section of duct near to the fan outlet); at cooling coils and heating coils (both before and after the coil). The actual location of the test holes shall be confirmed by the Designer and/or Commissioning Engineer either at the drawing approval stage (to be works drilled) or during the commissioning activity (to be site drilled). For practical access reasons the latter method is usually preferred. 20.7 Instrument connections Instrument connections shall be provided where shown on the contract drawings, suitably drilled or bossed and screwed as sizes specified. 20.8 Cleaning/maintenance Designers shall take specialist advice and then stipulate their requirements for the periodic internal cleaning/maintenance of ductwork and of the consequent need for adequate access for specialist cleaning equipment including the size, type and location/frequency of the actual access openings required. Appendix M sets out guidance notes for the consideration of cleaning access and also makes reference to the HVCA publication TR17 "Guide to Good Practice, Cleanliness of Ventilation Systems" which covers the subject in greater detail.

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20.9 Openings required for other purposes It shall be the designers responsibility to specify the location and size of any openings required other than those covered in this section. In the case of hinged access doors it shall be the designer's responsibility to indicate on the drawings the location and size of any hinged access doors required, ensuring that there is an area free of services and other obstructions to enable the door to be satisfactorily opened. Unless otherwise specified by the designer, openings should not be larger than 1350 mm high by 500 mm wide. Doors could open against the air pressure. Both the opening in the duct and the access door itself shall be adequately reinforced to prevent distortion. A suitable sealing gasket shall be provided, together with sufficient clamping type latches to ensure an airtight seal between the door and the duct. For safety reasons, the manufacturer shall incorporate means to prevent personnel being trapped inside the duct e.g. man access with operating handles both inside and outside the duct. 21 REGULATING DAMPERS 21.1 General Balancing dampers and control dampers are elements inserted into an air distribution system, or elements of an air distribution system. Balancing dampers permit modification of the air resistance of the system and consequently changing of the airflow rate. Control dampers control the airflow rate and in addition provide low leakage closure of the airflow. The designer shall specify damper locations and select the damper type as defined in 21.2 appropriate to the airflow, pressure and acoustic characteristics. 21.1.1 Balancing damper To achieve the required distribution of air in the ductwork system at inlets and/or outlets. For this purpose, the damper blades are set and locked manually in any required position between fully open and fully closed. 21.1.2 Control damper To secure dynamic control of the air flow in the ductwork system. In this function, the damper will always be power - actuated and may require to be modulated between fully open and fully closed, and to be capable of taking up any position between these extremes. In the fully open position, the damper should have a minimum pressure drop. In the fully closed position, it will not necessarily achieve a complete shut off. 21.2 Types of airflow control damper Air flow dampers of various types are available for specific purposes as follows. 21.2.1 Single-blade dampers (Single or double skin) Single-blade dampers shall consist of a single pivoted blade contained within a casing or section of ductwork. The blade shall be adjustable through a nominal 90° angle by means of a quadrant or similar operating mechanism. Where automatic control of the damper is required the spindle shall be extended to enable a powered actuator to be mounted.

Single-blade dampers (single-skin section) shall have a maximum duct width of 300 mm and a maximum duct height of 300 mm for rectangular ducts; and for circular ducts a maximum diameter of 315 mm. Single-blade dampers (double-skin section) are suitable for use in rectangular ducts, and shall have a maximum duct width of 1250 mm and a maximum height of 300 mm. 21.2.2 Multi-blade dampers (single or double skin) parallel or opposed blade Multi-blade dampers shall consist of a number of pivoted blades contained within a casing. The blades shall be adjustable through a nominal 90° angle simultaneously by interconnected linkage or gears, connected to a quadrant or similar operating mechanism. Where automatic control of the damper is required a spindle shall be extended to enable a powered actuator to be mounted. There is no restriction on the size of duct in which multi-blade dampers or damper assemblies may be used. Where dampers are required for blade lengths in excess of 1250 mm, the blades should be suitably reinforced or supported. No individual damper blade should exceed 200 mm in width. 21.2.3 Iris dampers Iris dampers shall consist of a number of radially inter-connected blades which open or close within a casing with duct connection spigots. The blades shall be simultaneously adjusted by a quadrant or similar operating mechanism. Iris dampers should be installed as specified by the manufacturer's operating and installation instructions, where the product is unidirectional with regard to airflow. Iris dampers are available for circular ducts only, in diameters up to 800 mm (It should be noted that the damper casing is approximately twice the diameter of the duct). 21.2.4 Backdraft dampers Air pressure operated uni-directional rectangular (single or multi-blade) with adaptors if fitted to circular or oval ducts. 21.2.5 Hit and miss dampers Two parallel adjacent plates each with multiple openings sliding against each other. The openings are designed to provide 50% air volume flow rates when they fully coincide. Used for simple operations up to 400 mm longest side. 21.2.6 Slide and blast gate dampers A damper used as a shut off facility, normally for use in circular ductwork with an external slide housing allowing a blade to be fully inserted to fully extended for maximum air flow. Generally available in cast/pressed formats up to 355 mm diameter and normally used in industrial exhaust applications. 21.3 Construction 21.3.1 Materials Dampers shall be constructed from steel, stainless steel, aluminium or synthetic materials. 48

All products shall be protected against corrosion as necessary and supplied in a fully finished condition as specified by the designer. 21.3.2 Dampers used in low and medium pressure systems The following recommendations apply to dampers forming an integral part of ductwork with pressure classification A and B air leakage limits. The dampers shall be constructed to prevent distortion and jamming in operation. The blades shall be sufficiently rigid to minimise movement when in the locked position. The blades shall be securely fixed to the operating mechanism. Spindles shall be carried in either nonferrous, synthetic or roller bearings. All balancing dampers shall have a locking device located on the outside of the case and shall give clear indication of the actual blade position. All penetrations of the duct shall be fitted with suitable seals where necessary. 21.3.3 Dampers used in high pressure systems Regulating dampers used in ductwork systems to pressure classification C shall meet the construction requirements specified in 21.3.1 and 21.3.2 with operating mechanisms out of the airstream. 21.3.4 Proprietary types of damper The use of any specific type of proprietary damper shall be confirmed by the designer. In all cases, proprietary dampers shall meet the relevant requirements of this specification. 21.3.5 Damper casings Duct damper casings shall be constructed to meet the minimum leakage limits specified for the ductwork system to which they are installed. In order to apply the square metreage leakage calculation as detailed in DW/143 A practical guide to Ductwork Leakage Testing, the reference casing area shall be taken as the perimeter size of the damper multiplied by the equivalent length of one metre eg. an 800 mm x 400 mm duct damper shall have a surface area for casing leakage performance calculated as follows; [(2 x 0.8) + (2 x 0.4)] x 1 = 2.4m2 casing area. Other performance and rating test methods for dampers and valves are specified in ISO5129 and BS/EN1751, and are referenced below: a) Leakage past a closed damper or valve BS/EN 1751 b) Flow rate/pressure requirement characteristics BS/EN 1751 c) Operational torque testing BS/EN 1751 d) Thermal transfer testing BS/EN 1751 e) Regenerated sound power levels ISO 5129 21.4 Installation Dampers shall be installed in accordance with any relevant ISO, EN or British Standard, local building regulations and national codes of practice as well as the manufacturer's recommendations.

22 FIRE DAMPERS 22.1 General Dampers are required in air distribution systems for fire containment. Generally they are called for where ducts penetrate walls or floors which form fire compartmentation. The damper assembly should have a fire resistance rating equal to that of the fire barrier it penetrates and shall be fire tested and rated to the time/temperature curve of BS476 part 20 and 22. 22.1 Types of fire dampers Fire dampers of various types are available for specific purposes, as follows: 22.2.1 Folding curtain Folding curtain fire dampers shall be constructed of a series of interlocking blades which fold to the top of the assembly permitting the maximum free area in the airway. The blades shall be held in the open position by means of a thermal release mechanism rated at 72°C ± 4°C. The fire damper must be able to close against static air conditions when mounted in either the vertical or horizontal planes. In the event of a signal from a remote sensor the fire damper blades shall be released and close the airway. A local excess temperature in the area of the fire damper shall, independent of any remote sensors, automatically release the blades and close the airway by means of the thermal release mechanism, electric solenoid or electromagnet. 22.2.2 Single blade Single blade fire dampers shall consist of a single pivoted blade within a fire resistant case. The blade shall be released from its open position by means of a thermal release mechanism rated at 72°C ± 4°C, electric solenoid, electromagnet(s) or other device. The blade shall close the airway by means of any one, or combination of, an eccentric pivot, balance weight(s) and/or spring(s), the spring element being incorporated within the damper or actuator mechanism. The fire damper shall be able to operate in either or both the vertical and horizontal planes. 22.2.3 Multi-blade Multi-blade fire dampers shall consist of a number of linked blades contained within a fire resistant case. The blades shall be released from their open position by means of either a thermal release mechanism rated at 72°C ± 4°C, or by the force applied from electrical solenoid(s), electromagnet(s), electrical/pneumatic actuator or other device.

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The blades shall close the airway by means of a spring(s), the spring element being incorporated within the damper or actuator mechanism. The fire damper shall be able to operate in either or both the vertical and horizontal planes. 22.2.4 Intumescent Intumescent fire dampers shall be constructed from strips of intumescent material formed into a lattice or from honeycomb material covered with intumescent paint. The damper shall fully seal when heat or flame is applied from either side. Note: these devices are generally used in door/partition low velocity applications. 22.3 Materials and construction The damper shall be constructed from steel or stainless steel or other approved material. Steel products shall be protected against corrosion and supplied in a fully assembled condition as specified by the designer. 22.4 Air leakage Fire damper casings shall meet the equivalent leakage performance standard specified for the ductwork system to which they are installed. Classes A, B and C are used to signify the leakage performance of the damper casing with the respective testing method illustrated and specified in BS/EN1751. In order to apply the square metreage leakage calculation as detailed in the standard, the reference casing area shall be taken as the perimeter size of the damper multiplied by an equivalent length of one metre eg. an 800 mm x 400 mm duct damper shall have a surface area for casing leakage performance calculated as follows: [(2 x 0.8) + (2 x 0.4)] x 1 = 2.4m2 casing area.

22.5 Location The effective formed barrier of the damper assembly shall be located within the structural opening. Where this is not possible the section of the casing outside a fire barrier must have a fire resistance not less than that of the fire barrier and be adequately supported/protected against the possibility of displacement/damage by impact. 22.6 Provision for expansion Damper assemblies generally include built-in clearance frames to meet the requirement that the casing be free to expand in the event of fire. The integrity of the fire barrier is maintained either by metal to metal contact or by fire resistant packing. Acceptable arrangements are shown in Figs. 78 and 79. 22.7 Installation Damper installation shall be in accordance with the manufacturer's recommendations and the impending HVCA Publication DW/TM3 - Guide to Good Practice, for the design for the installation of Fire and Smoke Dampers and any conflict between the two should be resolved and authorised by the designer responsible for the fire damper selection. 23 SMOKE DAMPERS 23.1 General Smoke dampers shall be constructed in such a manner as to restrict the spread of smoke and other products of combustion from one occupied space to another. The blade(s) shall overlap each other and/or include edge seals. The blade(s) shall be arranged to minimise the leakage of smoke. If degradable seals are fitted, care should be taken to establish the temperature range of the material used to ensure performance compatibility. 50

The smoke damper shall be able to operate in either or both the vertical and horizontal planes and close against dynamic air conditions. 23.2 Types of smoke damper Smoke dampers of various types are available for specific purposes, as follows: 23.2.1 Single blade Single blade dampers shall consist of a blade of smoke tight material held in either the open or closed position by a mechanical linkage releasing to close or open and seal against the damper case. The blade shall be mechanically connected to the actuator (electric or pneumatic) and shall be triggered by interfacing with a smoke detector or fire control panel. 23.2.2 Multi blade Multi blade dampers shall consist of blades of smoke tight material including the blade to blade seals, where fitted. The blades shall be mechanically linked to an actuator (electrical or pneumatic) to hold the blades in either the open or closed position. The actuator shall interface with a smoke detector or fire control panel and shall be so designed as to hold the blades close against the smoke seals, where fitted. 23.3 Materials and construction The damper shall be constructed from steel, stainless steel, other material or composite material with blades fitted to reduce the leakage of smoke and hot gases when the blades are in the closed position. Steel products shall be protected against corrosion and assembled in a fully finished condition as specified by the designer, in some circumstances controls may be supplied separately. 23.4 Air leakage Smoke damper casings shall be as Clause 22.4 23.5 Installation Damper installation shall be as Clauses 22.6 and 22.7. 24 COMBINATION SMOKE AND FIRE DAMPERS 24.1 General Combination smoke and fire dampers are required in air distribution systems to prevent the spread of smoke and hot gases from the fire zone and to maintain the integrity of a fire rated structure for a period compatible with that of the separating structure. They shall be tested and rated to BS476 Part 20 and 22. Reference maybe made to BS5588 Part 4 for specific smoke rating requirements. The closure of the fire damper under action of the thermal release element shall override all other subsequent signals. 24.2 Types of combination smoke and fire damper Combination smoke and fire dampers of various types are available for specific purposes, as follows: 24.2.1 Single blade Single blade combination smoke and fire

dampers shall consist of a single pivoted blade contained within a fire resistant case. The blade shall be released from its open position by means of either a thermal release mechanism rated at 72°C ± 4°C, or in addition operated by the force applied from electrical solenoid(s), electromagnet(s), electrical/pneumatic actuator or other device. The combination smoke and fire damper shall be able to operate in either or both the vertical and horizontal planes and close against dynamic air conditions. 24.2.2 Multi-blade Multi-blade combination smoke and fire dampers shall consist of a series of blades mechanically linked and connected to a damper actuator with manual, electric or pneumatic opening and spring loaded closure contained within a fire resistant case. The blades shall be released from their open position by means of either a thermal release mechanism rated at 72°C ± 4°C, or in addition operated by the force applied from electrical solenoid(s), electromagnet(s), electrical/ pneumatic actuator or other device. The combination smoke and fire damper shall be able to operate in either or both the vertical and horizontal planes and close against dynamic air conditions. 24.3 Materials and construction The combination smoke and fire damper case shall be constructed from steel, stainless steel, other material or composite material with compressible side seals fitted between the blade ends and the casing to reduce the leakage of hot gases when the blades are in the closed position. Steel products shall be protected against corrosion and supplied in a fully finished condition as specified by the designer. 24.4 Air leakage Damper casings shall be as Clause 22.4. 24.5 Installation Damper installation shall be as Clauses 22.6 and 22.7. 25 FLEXIBLE DUCTS 25.1 General Flexible duct connections shall be used in the fol lowing applications: · Terminal units · Fan coil units · Constant Volume/Variable Air Volume units · Grilles and Diffusers · Plenum boxes · Distribution ducts between the above items. They are available in a range of materials including metal, P V.C, fabric and with or without thermal insulation. The designer/contractor shall consider the

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following when selecting a particular type of flexible duct including: · Temperature range · Fire rating · Resistance to air flow · Airtightness characteristics · Length restrictions if applicable · Support requirements · Flexibility · Insulation values · System pressure. Flexible ducts are also available in twin wall format where the inner liner is perforated to provide acoustic properties or plain for thermal insulation. 25.2 Flexible ducts - Metal 25.2.1 Flexible ducts made of coated steel, stainless steel or aluminium are normally helically wound with a lock seam to form a corrugated duct capable of being bent without deforming the circular section. Bending is done by closing the corrugations in the throat and slightly opening the corrugations at the back of the bend. Some re-adjustment is possible but small radius bends cannot be straightened without leaving some distortion of the corrugations. Repeated bending is not recommended. The ducts shall be mechanically fastened at each end and particular care shall be taken to ensure that the required airtightness of the system is maintained. Fastenings should be as for rigid circular ducts Section 13.3 and Table 9. Sealing should be as Section 8.

25.2.2 Flexible ducts - Fabric Flexible ducts made from materials including P.V.C/Polyester laminate, Aluminium/Polyester laminate encapsulating high tensile steel wire helix are a very flexible form of construction. The length of flexible duct used should therefore be kept to a minimum, consistent with the particular application. Flexible ducts shall be fastened at each end using a propriety band. Care should be taken not to damage the flexible duct and to ensure that the required airtightness of the system is maintained. 25.3 Supports Flexible ducts have a higher resistance factor than conventional ductwork and should be supported in such a way that excessive sagging and consequently kinking of the duct is avoided. 25.4 Test Holes It is not practicable to make test holes or take test readings in metal or fabric flexible ducts. Where readings are required, the test holes should be made in rigid ductwork. 26 FLEXIBLE JOINT CONNECTIONS 26.1 General properties The material used for flexible joints must meet the designers requirement for temperature, air pressure, fire resistance, vibration, noise breakout when incorporated into a joint/connection and shall comply with the standard of airtightness specified for the ductwork system of which it forms part (See Fig. 80 for typical connection details). 26.2 Location Flexible joints are typically used at building 52

expansion joints and fan inlet/outlets. Any others required should be indicated on the design drawings. Care should be taken to maintain alignment across joints/connections. Joints/connections shall not be installed taught, but under a reasonable amount of compression. 26.3 Length Flexible joints shall be kept as short as practicable above a minimum effective length of 50 mm. In no case shall a flexible joint exceed 250 mm in length. 26.4 Connections to rectangular ducts With flanged rectangular connections, the flexible material shall be held in place with flat bar strips of not less than 2 mm thick attached to the flanges using suitable fixings. Where a proprietary brand of lightweight material is used with sheet metal fitted to either side consideration should be given to the size of connection it is used on and how it is fitted. The more heavy weight type of flexible material may also be obtained formed into a channel section with corners fitted and stitched to give a neat airtight joint. For spigot connections the flexible material shall be held in place with flat bar strips of not less than 2 mm thick. 26.5 Connections to circular ducts With flanged circular connections the flexible material shall be held in place with alternative flat bar rings, flat bar clip rings or proprietary clip bands with screw or toggle fittings. Where a proprietary brand of light weight flexible with metal to either side is used, careful consideration must be given to sealing when fitting to spirally-wound ducts. 26.6 Connections to oval ducts Special consideration should be given to the construction but the type of joint applies as for circular ducts except proprietary clip band with screw or toggle fastening is not suitable on oval ducts. 27 PROTECTIVE FINISHES Unless otherwise stated all ductwork will be manufactured in pre-galvanised sheet steel, aluminium or stainless steel as specified, with prime coating where applicable (see 27.3.5). Any additions to this would normally be the responsibility of others. Any special coating/paint finishes to be provided by the ductwork contractor must be advised by the designer. 27.1 Galvanizing after manufacture Galvanizing after manufacture is not recommended for general use, as distortion of the duct or fitting is probable, thus making if difficult to achieve an airtight joint. Galvanizing after manufacture is, however, an acceptable protective finish for circular pressed fittings and external ductwork exposed to atmosphere. Where galvanizing after manufacture is specified, it shall be to BS 729, see Appendix E. No paint protection is required.

27.2 Metal spraying Zinc or aluminium spraying shall be to BS EN 22063 (1994), Part 1. 27.3 Paints 27.3.1 Surface preparation and paint application Surface preparation of the metal and paint application shall be in accordance with the paint manufacturer's recommendations. 27.3.2 Making good welding damage Galvanizing or other metallic zinc finish damaged by welding shall be suitably cleaned and painted with one coat of zinc-rich or aluminium paint. 27.3.3 Ducts made from pre-galvanized sheet or coil Ducts and profile sections made from pregalvanized sheet or coil will have no need for paint or further protection where located inside a building. This also applies to exposed cut edges in accordance with criteria laid down by British Steel PLC. See Appendix N Bibliography. 27.3.4 Ducts made from other types of mild steel sheet Where circumstances require ducts to be made from mild steel sheet or coil other than the foregoing, protective requirements shall be specified by the designer. 27.3.5 Untreated steelwork profiles and sheet Any plain mill finish unprotected mild steel such as rolled steel sections and/or sheet used for flanging, stiffeners, supports and duct walls must be treated. Treatment would be an appropriate primer such as zinc rich, zinc chromate, red oxide or aluminium paint. 28 CONNECTIONS TO BUILDING OPENINGS 28.1 Forming and finishing building openings are not the responsibility of the ductwork contractor and the notes that follow are for guidance purposes only. 28.1.1 Openings in brick, block or concrete walls shall have inset frames to provide a suitable means of fixing grilles, louvres, masking flanges or the flanged ends of ductwork. The inset frames shall be constructed to maintain the structural integrity of the wall and where applicable cavities shall be suitably lined. 28.1.2 Openings in dry lining partitions shall have inset frames as in 28.1.1. 28.1.3 Openings in cladding walls and roofs shall have flanged sleeves/frames to provide a suitable means of fixing as in 28.1.1. 28.1.4 Horizontal and vertical openings that are exposed to outside atmosphere shall be provided with a suitable weathering finish at the external face especially if profiled cladding is involved.

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28.1.5 Timber framed openings are not permitted in fire compartment walls. 28.2 Ductwork connections to building openings shall have a flange of suitable profile to permit practical fixing to the opening frame. In selecting the profile, consideration shall be given to Table 2 in this specification relating to duct size and rating. Gasket strip or sealer shall be applied between the flange and building opening frame. 29 INTERNAL DUCT LININGS 29.1 General Where an acoustic or thermal lining to ductwork is specified it should preferably be fitted at works. Before duct manufacture it should be clarified that specified external duct dimensions allow for the lining thickness. Any form of lining should have fire characteristics having minimum Class 0 rating and must be specified by the Designer for material type, thickness, and application method. 29.2 Lining Application Considerations Prior to the application of any lining the internal duct surface must be thoroughly cleaned to provide a dust free dry surface which may additionally be degreased. Securing the lining to the internal duct surface can be achieved in several ways including applied adhesive, self adhesive and physical methods such as fasteners in conjunction with surface washers at a specified square pitch. Adjacent sections of lining should abut with minimal gap and integral or separate surface finish lap to such joints and or gap filling proprietary products being applied. This procedure is to obviate any particle migration. During application and any curing, consideration should be given to ambient temperature and humidity requirements. In all circumstances linings should be fitted to material manufacturer's recommended methods. 29.3 Circular ducts Lining circular ducts is impractical and is not recommended. 29.4 Cleaning and maintenance Designers should be aware of the possible porous/ fibrous surface nature of linings as they may present practical/hazardous problems in cleaning and maintenance. Reference in this respect should be made to the following HVCA Publications i) DW/TM2 Guide to Good Practice, Internal Cleanliness of New Ductwork Installations. ii) TR17 Guide to Good Practice, Cleanliness of Ventilation Systems.

30 THERMAL INSULATION 30.1 The provision and application of thermal insulation to ductwork is not normally the responsibility of the ductwork contractor. 30.2 Where ductwork is required to be preinsulated, the specification should be agreed with the designer. 30.3 Where the temperature of the air within the duct is at any time low enough to promote condensation on the exterior surface of the duct and cause moisture penetration through the thermal insulation, vapour sealing may be called for, and in this case the most important requirement is to limit penetration of the seal. The extent of any vapour sealing of ductwork thermal insullation and the support method to be used must be clearly specified in advance by the designer. 30.4 For detailed information on the thermal insulation of ductwork, reference should be made to BS 5422:1990 which covers the specification for thermal insulation materials on pipes, ductwork and equipment (in the temperature range -40°C to +700°C) and BS 5970:1992 which is a Code of practice for thermal insulation of pipework and equipment (in the temperature range -100°C to +870°C). 31 KITCHEN VENTILATION 31.1 For detailed information reference should be made to HVCA Publication, Guide to good Practice for Kitchen Ventilation Systems DW/171. 32 FIRE RATED DUCTWORK 32.1 For information see Appendix D of this specification. 33 STANDARD COMPONENT DRAWINGS AND ABBREVIATIONS 33.1 The illustrations in this section not only highlight, where applicable, geometric limitations for the design and manufacture of ductwork components but also recommend standard drawing representation, terminology and abbreviations for both ductwork components and some of the more commonly used ancillary/plant items. 33.2 Designers and surveyors should note that bills of quantities should provide a full description

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Part Eight-Appendices

APPENDIX A - AIR LEAKAGE FROM DUCTWORK

To be read in conjunction with DW/143 A practical guide to Ductwork Leakage Testing

CAUTION As highlighted in both this document and DW/143, not enough emphasis can be placed on the fact that, except for high pressure class C, the much tighter ductwork constructional standards brought about by the general acceptance of DW/142 have virtually negated the requirement for leakage-testing. It is essential to realise that except where it is mandatory this document is not an endorsement of the routine testing of ducts but purely a guide to outline the procedures for conformity with the air leakage limits in Table 1. When proper methods of assembly and sealing of ducts are used, a visual inspection will ordinarily suffice .for verification of a well engineered and acceptably airtight construction. WHERE NOT MANDATORY, DUCT LEAKAGE TESTING IS GENERALLY AN UNJUSTIFIED AND SUBSTANTIAL EXPENSE.

A.1 INTRODUCTION Leakage from ducted air distribution systems is an important consideration in the design and operation of ventilation and air conditioning systems. A ductwork system that has limited air leakage, within defined limits, will ensure that the design characteristics of the system can be maintained. It will also ensure that energy and operational costs are maintained at optimum levels. Ductwork constructed and installed in accordance with DW/144 should minimise a level of air leakage that is appropriate to the operating static air pressure in the system. However, it is recognised that the environment in which systems are installed is not always conducive to achieving a predictable level of quality in terms of system airleakage and it is therefore accepted that designers may sometimes require the systems to be tested in part or in total. It should be recognised that the testing of duct systems adds a significant cost to the installation and incurs some extra time within the programme (See 4.1 and 6.4 re mandatory testing). A.2 DUCT PRESSURE Ductwork constructed to DW/144 will be manufactured to a structural standard that is compatible with the system operating pressure. There are three classes of duct construction to correspond with the three pressure classifications: Class A Low pressure ducts suitable for a maximum positive operating pressure of 500 Pascals and a maximum negative pressure of -500 Pascals. Class B Medium pressure ducts suitable for a maximum positive operating pressure of 1000 Pascals and a maximum negative pressure of -750 Pascals. Class C High pressure ducts suitable for a maximum positive operating pressure of 2000 Pascals and a maximum negative pressure of -750 Pascals.

A.3 LEAKAGE FROM DUCTWORK Leakage from sheet metal air ducts occurs at the seams and joints and is therefore proportional to the total surface area of the ductwork in the system. The level of leakage is similarly related to the air pressure in the duct system and whilst there is no precise formula for calculating the level of air loss it is generally accepted that leakage will increase in proportion to pressure to the power of 0.65. The effect of air leakage from high pressure/velocity ductwork is critical in terms of system performance, energy consumption and the risk of high frequency noise associated with leakage. These problems are less critical with medium pressure/velocity systems, but should be considered. Low pressure/velocity ducts present the lowest risk in terms of the effect of leakage on the effective operation of the system. A.4 SYSTEM LEAKAGE LOSS As there is no direct relationship between the volume of air conveyed and the surface area of the ductwork system required to match the building configuration it is difficult to express air leakage as a percentage of total air volume. Similarly, the operating pressure will vary throughout the system and as leakage is related to pressure the calculations are complex. However, it is generally accepted that in typical good quality systems the leakage from each class of duct under operating conditions will be in the region of: Class A low pressure 6% Class B medium pressure 3% Class C high pressure 2%

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A.5 SPECIFYING AIR LEAKAGE TESTING Respecting both the cost and programme implications associated with testing ducts for leakage, the designer may, for example indicate that a particular system is tested as follows: a) High pressure ducts - all tested. b) Medium pressure ducts - 10% of the ductwork shall be selected at random and tested. c) Low pressure - untested. In the case where a random test is selected for medium pressure ducts the following clause is suggested for inclusion by the designer. The designer shall select at random a maximum of 10% of the duct system to be tested for air leakage. The duct shall be tested at the pressure recommended in Table 17 of DW/144

for the classification for the section of the ductwork that is to be tested. The tests shall be carried out as the work proceeds and prior to the application of thermal insulation. In the event of test failure of the randomly selected section, the designer shall have the right to select two further sections at random for testing. Where successive failures are identified there shall be a right to require the contractor to apply remedial attention to the complete ductwork system. The contractor shall provide documented evidence of the calculations used to arrive at the allowable loss for the section to be tested and the client, or his agent, shall witness and sign the results of the test.

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A.6 SPECIAL CASES There may be situations on a project where circumstances dictate that special consideration be given to containing air losses, e.g. a long run of ductwork may incur a disproportionate level of air loss. In cases such as this example the designer can specify an improved standard of airtightness, i.e. 80% of allowable loss for Class `B' ducts. The designer should not specify a Class `C' test at Class `C' pressure for a Class `B' duct. A.7 SUGGESTED RANGE OF TESTING · High pressure ducts 100% test · Medium pressure ducts See A5 · Low pressure ducts Untested · Exposed extract systems Untested · Ceiling void extract systems Untested · Secondary ducts from VAV or fan coil units Untested · Flexible ducts Untested · Final connections and branches to grilles and diffusers Untested A.8 TESTING OF PLANT ITEMS Items of inline plant (eg. Figs. 168 to 175) will not normally be included in an air leakage test. The ductwork contractor may include such items in the test if the equipment has a certificate of

conformity for the pressure class and air leakage classification for the system under test. A.9 DESIGNER'S CALCULATIONS The designer can calculate with reasonable accuracy the predicted total loss from a system by: a) Calculating the operating pressure in each section of the system. b) Calculating the surface area of the ductwork in each corresponding pressure section. c) Calculating the allowable loss at the operating pressure for each section of the system (see table 17 for allowable leakage figures). A.10 VARIABLE PRESSURES IN SYSTEMS Designers can achieve significant cost savings by matching operating pressures throughout the system to constructional standards and appropriate air leakage testing, e.g. the practice of specifying construction standards for whole duct systems based on fan discharge pressures may incur unnecessary costs on a project. For example, some large systems could well be classified for leakage limits as follows: Plant room risers Class C Main floor distribution Class B Low pressure outlets Class A

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APPENDIX B - IDENTIFICATION OF DUCTWORK

Note The information given in this Appendix is for the guidance of mechanical services contractors, consulting engineers, etc. The identification of ductwork does not form part of the work carried out by the ductwork contractor unless required by the designer in the job specification. B.1 GENERAL B.1.1 Introduction With the increasing complexity of ventilation and air conditioning systems, it is becoming more important to ensure ready identification of ducts for the purposes of commissioning, operation and maintenance of systems. The purpose of these recommendations is to lead towards the use and standardisation of a system of identification for ducts for the benefit of designers, contractors and clients. B.1.2 Scope B.1.2.1 These recommendations deal with the identification of ducts for ventilation, air conditioning and simple industrial exhaust systems. They do not include piped gas systems such as those dealt with in BS 1710 1984, nor ductwork systems for industrial processes, although the general considerations and intentions could be extended with the agreement of the client to cover such systems. B.1.2.2 The method is designed to identify the air being conveyed, the direction of flow, the destination of the air and/or the location or nomenclature of the plant where the air was treated. With small or simple plants, it may not be strictly necessary to provide identification because the function is apparent, but it is considered advisable to do so because this will increase familiarity with the labelling system and also because the nature and direction of air flow may not always be apparent. B.2 IDENTIFICATION B.2.1 Location To be effective the identification must be placed where it can be easily seen and at positions where identification will be required. To ensure that the symbols are seen, the following points should be considered. B.2.1.1 The symbols should be on the surfaces which face the positions of normal access to the completed installation. B.2.1.2 The symbols should not be hidden from view by structural members, other ducts, plant, or other services distribution systems. B.2.1.3 The symbols should be placed, where possible, where there is adequate natural or artificial light. B.2.2 Identification symbols will be needed in plant rooms and remote areas. Symbols should occur frequently enough to avoid the need for ducts to be traced back. Symbols should be placed at any service and access points to the distribution system, including points where the distribution system has reduced to a single duct. B.2.3 Colour coding The choice of colours has been based on the need to provide: B.2.3.1 Strong contrasting colours which are recognisable even though covered with dust. B.2.3.2 Contrast between the symbol colour and the base colour of the duct. Usually the base colour metallic grey of galvanized or aluminium sheet or foil sheathing, or the white, pale grey, or buff paint on the insulation is a neutral colour against which the recommended symbol colours will stand out. B.2.4 The recommended colours are given in Table 18. The colour coding indicates the type of air being conveyed.

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B.2.5 For conditioned air, two symbols (one red, one blue) may be used, or a single symbol coloured part red, part blue. B.2.6 If a finer grading than that given in Table 18 is required, as for instance in a laboratory with two separate contaminated air exhaust systems, it is recommended that the type colour be used with, say, a stripe of a second colour. Where the duct contents constitute a hazard, a symbol as given in BS 1710 1984 should be added to the type colour. B.2.7 Direction of flow B-.2.7.1 The form of symbol chosen indicates direction. It is an equilateral triangle (see Fig. 179) with one apex pointing in the direction of air flow. Where the boundaries of the duct are not visible, two triangles should be arranged in line ahead to indicate direction of flow. B.2.7.2 The size of the symbol will depend on the size of the duct and the viewing distance. The recommended minimum size for normal use is 150 mm length of side.

of the plant. The plant itself must be clearly numbered to correspond. Letters for Supply, Flow, Extract, etc., should not be added because identification will be clear from the colour symbol. Thus confusion between `S' for Supply and `S' for South will be avoided.

B.2.8.3 Where identification of the space is by room number, this must be agreed with the user who otherwise may have numbered the rooms differently. Some examples of further identification systems are given in Table 19. B.2.8.4 The letters and numbers should be in either black or white, whichever gives the better contrast. They should be marked on the colour symbol or immediately adjacent to it. The size of the figures will depend on how easily they can be seen, but should not be less than 25 mm high. B.2.9 Explanatory chart An explanatory chart shall be included in the 0 (Operating) and M (Maintenance) manual and shall also be kept in the plant room or other convenient place. The chart should show and explain the colour symbols used on the installation and where appropriate the figure and letter codes used for further identification. B.3 METHOD OF APPLICATION OF SYMBOLS B.3.1 Several methods are available for applying the symbols, the main factor being that the symbol is permanently affixed. Suitable methods are: B.3.1.1 Painting, using stencilled letters and figures. B.3.1.2 Self-adhesive plastics or transfers with water soluble backing. (It is important to ensure that the surface is smooth and clean and that the adhesion will not deteriorate due to the surrounding atmosphere.) B.3.1.3 Purpose-made plastics or metal labels. 81

B.2.8 Further identification B.2.8.1 On small or simple installations where there is one plant and one or two zones and therefore little chance of confusing the ducts, it will not be necessary to provide identification other than the colour symbol. On large complex installations with many zones, widely branched distribution systems or several plants, further identification is necessary. In this connection a plant refers to the ductwork and equipment associated with one particular fan. B.2.8.2 The further information to be given will normally be the space served by the duct and in some cases the associated plant. The information should be given as briefly as possible using commonly accepted forms such as a number indicating which floor of a building. The plant identification should always be preceded by the letter `P' to avoid confusion between the number of the floor and the number

APPENDIX C - GUIDANCE NOTES FOR THE TRANSPORT, HANDLING AND STORAGE OF DUCTWORK

It is recommended that before a contract is finalised, that consideration is given to the subject of site access, material handling and storage as they have a strong influence on the cost efficiency of the overall activity of ductwork installation. C.1 Transport Large capacity vehicles with high-sided open or closed-top bodies are the most suitable for the transport of ductwork. Careful consideration should be given to the unloading of transport on site as not all sites benefit from the material handling and access facilities that exist in a manufacturing workshop such as cranes, fork-lifts or loading bays. Site handling facilities along with vehicular access restrictions may influence the type and size of transport to be utilised. Lengths of ductwork should be positioned so as to avoid crushing. Lengths with projections, such as branches and bends, flanges, girths, damper quadrants should be loaded so as to avoid damage to adjacent duct panels. In some cases, particularly on contracts calling for repetitive sizes, the use of timber jigs and spacers may be justified. Where reduced bulk and greater protection are major factors, such as consignments for export, transporting ductwork in `L' shape sections may justify the increased site assembly costs. C.2 Handling To minimise the risk of damage, duct sections should be clearly identified and deliveries to site should be closely linked to the installation programme, so as to avoid accumulation of unfixed ductwork and minimise double handling. It is important to recognise that ductwork panels, joints and corners are susceptible to damage and care must be taken when handling such material through a site. During handling, individual items of ductwork may be liable to slight cross sectional deformation until they become an integral part of a completed ductwork system. Whilst this may temporarily detract from its intended appearance, this deformation will not have any affect on the functionality of the finally assembled system. Installation of ductwork and associated plant items will inevitably involve manual handling. The responsibility of employers and employees to assess the risk of personal injury during manual handling operations is set out in the H.S.E. publication L23, Guidance on Manual Handling Regulations 1992. C.3 Site storage Adequate floor space must be provided within the building for the site storage of ductwork. Such storage shall make due allowance for the storage of ductwork in stacks such that access between them is of sufficient width to permit the removal of items without interference to adjoining stacks. Ductwork components should be positioned so as to avoid crushing. Ductwork of small panel size may be stored horizontally; however care should be exercised to ensure that stack sizes are limited to within the structural strength of the duct sections to prevent distortion of the lower sections within the stack. C.4 Internal cleanliness of new ductwork The site storage of ductwork introduces the important consideration of maintaining the internal cleanliness of the ductwork. Reference should be made to HVCA document: · DW/TM2 Guide to Good Practice - Internal Cleanliness of New Ductwork Installations. If the above conditions can not be satisfied consideration should be given by the designer to amending the specification to include for "Post Installation Cleaning" as covered by the HVCA document: · TR17 Guide to Good Practice - Cleanliness of Ventilation Systems.

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APPENDIX D - DUCTWORK SYSTEMS AND FIRE HAZARDS

D.1 Fire and smoke containment/hazards are factors which influence the design and installation of ductwork systems. Information concerning fire protection systems is laid down in BS 5588, Fire Precautions in the design and construction of Building Part 9 (1989) Code of Practice for Ventilation and Air Conditioning Ductwork and tested in accordance with BS 476 Part 20 (1987) and BS 476 Part 22 (1987) for Fire and Smoke Dampers and British Standard 476 Part 24 (1987) - ISO 6944 - (1985) for Fire Rated Ductwork. D.2 Building Regulations in the United Kingdom require that new buildings be divided into fire compartments in order that the spread of smoke and fire in the building is inhibited, and to stop the spread of smoke and fire from one compartment to another, for given periods of time as specified by the Building Regulations 1991 (Approved Document B). D.2.1 There are three methods of fire protection, related to ductwork systems as given in BS 5588 Part 9 (1989). Method 1 - Protection using Fire Dampers The fire is isolated in the compartment of origin by the automatic or manual actuation of closures within the system. Fire dampers should, therefore, be sited at the point of penetration of a compartment wall or floor, or at the point of penetration of the enclosure of a protected escape route. Fire dampers should be framed in such a way as to allow for thermal expansion in the event of fire, and the design must provide for the protection of any packing material included. Standard types of fire dampers and frames are described in Section 22 of this specification. For further information refer to the impending HVCA publication DW/TM3, `Guide to Good Practice for the Design for the Installation of Fire and Smoke Dampers'. Method 2 - Protection using Fire Resisting Enclosures Where a building services shaft is provided through which the ventilation ductwork passes and if the shaft is constructed to the highest standard of fire resistance of the structure which it penetrates, it forms a compartment known as a protected shaft. This allows a complicated multiplicity of services to be transferred together through a shaft transversing a number of compartments and reaching remote parts of the building, without requiring further internal divisions along its length. The provision of fire dampers is then required only at points where the ventilation duct leaves the confines of the protected shaft. However, if there is only one ventilation duct and there are no other services within the protected shaft, between the fire compartment and the outside of the building, no fire dampers will be required. 83 Method 3 - Protection using Fire Resisting Ductwork The ductwork itself forms a protected shaft. The fire resistance may be achieved by the ductwork material itself or through the application of a protective material provided that the ductwork has been tested and/or assessed to BS476 Part 24 with a fire resistance, when tested from either side that should not be less than the fire resistance required for the elements of construction in the area through which it passes. It should also be noted that the fire resisting ductwork must be supported with suitably sized and designed hangers, which reflect the reduction in tensile strength of steel in a fire condition i.e: Fire resisting ductwork rated at 60 minutes (945°C), reduces the tensile strength from 430 N/mm2 to 15 N/mm2. Fire resisting ductwork rated at 120 minutes (1,049°C) tensile strength reduced to 10 N/mm2. Fire resisting ductwork rated at 240 minutes (1,153°C) tensile strength reduced to 6 N/mm2. Where the fire resisting ductwork passes through a fire compartment wall or floor, a penetration seal must be provided which has been tested and/or assessed with the ductwork to BS476 Part 24, to the same fire rating as the compartment wall through which the fire resisting ductwork passes. It should also be noted that where the fire resisting ductwork passes through the fire compartment wall or floor, the ductwork itself must be stiffened to prevent deformation of the duct in a fire to: a) maintain the cross-sectional area of the duct b) ensure that the fire rated penetration seal around the duct is not compromised. D.2.2 - Main areas within building where Ductwork should be fire protected The following notes are for guidance only, and it should be noted that authority rests with the Building Control Officer and/or the Fire Officer responsible for the building. Reference on the folowing systems should also be made to the current Building Regulations. a. Smoke Extract Systems: If the ductwork incorporated in a smoke extract system is wholly contained within the fire compartment, it must be capable of resisting the anticipated temperatures generated through the development of a fire. BS 476 Part 24 also requires ductwork, which is intended as a smoke extract, must retain at least 75% of its cross-sectional area within the fire compartment. If the ductwork penetrates a fire resisting barrier, it must also be capable of providing the same period of fire resistance. b. Escape Routes covering Stairways, Lobbies and Corridors All escape routes must be designed so that the building occupants can evacuate the building

safely in the case of fire. Ductwork which passes through a protected escape route must have a fire resistance at least equal to the fire compartment through which the ductwork passes, either by the use of fire dampers or fire resisting ductwork. c. Non Domestic Kitchen Extract Systems Where there is no immediate discharge to atmosphere, i.e. the ductwork passes to atmosphere via another fire compartment, fire resistant ductwork must be used. Kitchen extract ductwork presents a particular hazard as combustible deposits such as grease are likely to accumulate on internal surfaces, therefore, all internal surfaces of the ductwork must be smooth. A fire in an adjacent compartment, through which the ductwork passes, could lead to ignition of the grease deposits, which may continue through the ductwork system, possibly prejudicing the safety of the kitchen occupants. For this reason consideration must be given to the stability, integrity and insulation performance of the kitchen extract duct which should be specifically tested to BS 476 Part 24 for a kitchen extract rating. · Access doors for cleaning must be provided at distances not exceeding 3 metres. · Fire dampers must not be used. · Use of volume control dampers and turning vanes are not recommended. Further information on kitchen extract systems will be found in the HVCA publication DW/171 Specification for Kitchen Ventilation Systems. d. Enclosed Car Parks - which are mechanically ventilated Car Parks must have separate and independent extract systems, because of the polluted nature of the extract air. Due to the fire risk associated with car parks, these systems should be treated as smoke extract systems and therefore maintain a minimum of 75% cross-sectional area under fire conditions in accordance with BS 476 Part 24. Fire dampers must not be installed in extract ductwork serving car parks. e. Basements - Ductwork from Basements must be Fire Rated If basements are compartmented, each separate compartment must have a separate outlet and have access to ventilation without having to gain access (i.e. open a door to another

compartment). Basements with natural ventilation should have permanent openings, not less than 2.5% of the floor area and be arranged to provide a through draft with separate fire ducts for each compartment. f. Pressurisation Systems Pressurisation is a method of restricting the penetration of smoke into certain critical areas of a building by maintaining the air at higher pressures than those in adjacent areas. It applies particularly to protect stairways, lobbies, corridors and fire fighting shafts serving deep basements as smoke penetration to these areas would inhibit escape. As the air supply creating the pressurisation must be maintained for the duration of a fire, fire dampers cannot be used within the ductwork to prevent the spread of fire. Any ductwork penetrating fire resisting barriers must be capable of providing the same period of fire resistance. g. Hazardous Areas There are other areas within the building where the Building Control Officer or the Fire Officer could state a requirement for fire resisting ductwork, eg. areas of high risk, Boiler Houses, Plantrooms, Transformer Rooms etc. D.2.3 Cautionary note to all Ductwork Designers/ Manufacturers: Ductwork constructed to DW/144 Standard has no tested fire resistance. General purpose ventilation/air conditioning ductwork and its ancillary items do not have a fire rating and cannot be either utilised as or converted into a fire rated ductwork system unless the construction materials of the whole system including supports and penetration seals are proven by test and assessment in accordance with BS 476 Part 24. In the case where galvanised sheet steel ductwork is clad by the application of a protective material, the ductwork construction must be as type tested and comply with the protective material manufacturers recommendations, eg. gauge of ductwork, frequency of stiffeners and non-use of low melting point fasteners or rivets. Sealants, gaskets and flexible joints should be as tested and certificated in accordance with BS 476 Part 24 and comply with the manufacturers recommendations. Careful consideration must also be given to the maximum certificated size tested to BS 476 Part 24 and the manufacturers recommendations should always be followed.

This appendix incorporates information given in the A.S.F.P publication `Fire Rated and Smoke Outlet Ductwork: An Industry Guide to Design and Installation' available from Association for Specialist Fire Protection, Association House, 235 Ash Road, Aldershot, Hampshire GU 12 4DD (Telephone: 01252 21322 Fax: 01252 333901)

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APPENDIX E - HOT DIP GALVANIZING AFTER MANUFACTURE

E.1 General E.1.1 For Hot Dip galvanizing after the fabrication of any article it is necessary to appreciate the nature of the process, including the surface preparation of the object to be treated and the precautions to be taken in design, fabrication and handling. E.1.2 Hot Dip galvanizing involves dipping the object into a bath of molten zinc (at a temperature of between 445° and 465° C), and it is necessary for the zinc to cover the whole of the surface leaving no gaps in the coating. E.2 Design and fabrication E.2.1 Rectangular ductwork must be fabricated using all welded construction techniques with vented flanges and stiffening frames (see E.2.3) as mechanical fixing and lock-forming techniques are not compatible with the galvanising process. In the course of dipping into the molten zinc bath, unsightly panel distortion will occur due to the relief of inherent stress in the steel sheet or of any stresses that may have been built into the item during fabrication, or indeed of any stresses introduced during the handling, loading or unloading of the item. Table 20 indicates the minimum requirements for the construction of rectangular ductwork. E.2.2 It is essential to have a free flow of the molten zinc over the object to be galvanized, together with quick and complete drainage of the molten metal. Because of the high temperature involved, the object to be galvanized should be as rigid as possible, either by the use of sufficiently heavy sheet or by stiffening or bracing, or both. E.2.3 Any sealed hollow section or cavity must be adequately vented in order to obviate any possibility of explosion. Holes of sufficient size (See E.2.4) in vertical members must be provided diagonally opposite each other, top and bottom of the member. E.2.4 Vent holes should be of sizes as follows: Size of Minimum hollow diameter of section vent end (dia. or side) drainage holes mm mm Up to 25 10 50 to 100 16 100 to 150 20 Over 150 25 E.2.5 Stiffeners should desirably have their corners cropped so as to allow a free flow of zinc. Stiffeners should be rolled steel angle, uncoated. E.3 Surface preparation before galvanizing E.3.1 The steel surface to be galvanized must be chemically clean before dipping to ensure a continuous coating. This is mainly achieved at the galvanizer's works by pickling in an acid bath and fluxing before the article goes into the zinc bath. How

ever, the pickling process does not generally remove grease, oil or oil-based paint, and such substances should be removed by the fabricator by the use of suitable solvents before the object to be treated is delivered to the galvanizing works. Any surface rust that develops on the object between the time of treatment by the fabricator and delivery to the galvanizing works is not important, as this is cleaned off by the acid pickling process. E.4 Handling and storage after galvanizing E.4.1 While a galvanized surface will not develop rust in the ordinary sense as long as the zinc coating is undamaged, zinc is subject to what is known as `wet storage stain,' which is a white powdery deposit on the zinc surface. Wet storage stain can arise from the stacking of articles when wet, acid vapours, the effect of salt spray, the reaction of rain with flux residues, etc. The damage to the zinc coating is negligible in most cases. When the deposits are heavy, these should be removed by brushing with a stiff bristle or wire brush. E.4.2 Galvanized articles should therefore not be stacked or loaded when wet; they should preferably be transported under cover or shipped in dry, well ventilated conditions, inserting spacers (but not resinous wood) between the galvanized articles. E.4.3 When stored on site or elsewhere, care should be taken to avoid resting the galvanized article on cinders or clinker, as the acid content of these substances will attack the zinc surface. E.5 Subsequent finishing E.5.1 Paint finishing subsequent to galvanizing is sometimes required either for additional protection or for decorative reasons. Galvanised surfaces require chemical pretreatment prior to painting. Examples of such a treatment are T-Wash and Etch Primer Types. Advice should be sought from the paint manufacturer.

This Appendix incorporates information given in publications available from the Galvanizers' Association, 6 Wrens Court, 56 Victoria Road, Sutton Coldfield, West Midlands B72 1SY 85

APPENDIX F - STAINLESS STEEL FOR DUCTWORK

F.1 General F.1.1 Stainless steel is not a single specific material: There is a large family of stainless steels with varying compositions to suit specific applications, but all contain at least 11 % of chromium as an alloying addition. F.1.2 Modern stainless steels have a combination of good formability and weldability, and can be supplied with a variety of surface finishes (see E4.1 below) They have been developed to cover a wide range of structural uses where high resistance to corrosion and low maintenance costs are demanded. F.1.3 Ductwork applications for which stainless steels are particularly suited include those where a high integrity inert material is essential; where a high degree of hygiene is required; in the chemical industries where toxic or hazardous materials may be contained; in nuclear and marine applications (e.g. on offshore platforms). Stainless steels also find application in exposed ductwork where their finish can be used to aesthetic advantage. F.2 Grades of stainless steel F.2.1 The grades of stainless steel most commonly used for ductwork applications are among those covered currently by BS 1449, Part 2. However, a European Standard, will supersede this British Standard. New designations of the most common steel grades are given in Table 21. In some cases there are minor differences in chemical composition between the BS and EN grades. Before a grade is specified, the nature of the interior and exterior environments of the ductwork system should be taken into account. The steels described below cover most normal applications. However, advice on specific corrosion risks should be taken if the ductwork is to be installed in a chemically contaminated atmosphere, or is to be used to transport contaminated air, particularly if there is a risk of internal condensation. More highly alloyed grades of stainless steel with enhanced corrosion resistance are available if required. The commonly used steels divide into two main families; the lower alloy ferritic 11-18% chromium stainless steels are magnetic. The austenitic, 18% chromium, 9% nickel steels have generally better corrosion resistance and are non- or only slightly magnetic. F.2.2 The more commonly used stainless steels and their characteristics are described below. F.2.2.1 11.5% chromium ferritic steel with a titanium addition, 409S 19, New designation 1.4512, X2CrTi12. This, and related grades, are among the leanest alloyed of the stainless steels. Forming characteristics are similar to those of mild steel, so it can be worked using conventional practices. The composition and processing of the steel is usually adjusted by the manufacturer to balance forming response, weldability and corrosion resistance. It is readily welded in thin sheet form and, since it does not form a hardened weld HAZ, no postweld heat treatment is required. It is widely used for automotive exhaust system parts and is suitable for a range of ducting and structural applications in mildly corrosive applications. F.2.2.2 17% chromium ferritic steel, 430S17, New Designation 1.4016, x6Cr 17. Forming and general characteristics are similar to the 409 grade, but the higher chromium level confers better general corrosion resistance. F.2.2.3 18% chromium, 9% nickel austenitic stainless steels. A widely used grade is 304S15, New Designation 1.4301, x5CrNil8-10. There are compositional variants within this family, designed to give specific formability and welding characteristics. All are weldable and have good general corrosion resistance to normal and mildly corrosive atmospheres. They are ductile and formable, but forming loads are higher than for mild steels and suitable, robust equipment is required. F.2.2.4 17% chromium, 11% nickel, 2% molybdenum austenitic steel, a widely used grade of this type is 316S31, New Designation 1.4401, x5CrNiMo17-11-2. This steel has a significantly higher corrosion resistance than the standard 18% chromium, 9% nickel steels and is suitable for use in more aggressive environments such as are met in ductwork in process plants. However, more highly alloyed stainless steels with better corrosion resistance are also available and the advice concerning aggressive environments given under section F.2.1 above should be noted. F.3 Availability Stainless steel is supplied in a wide range of thicknesses, from 0.4 mm for cold-rolled sheet and coil, and from 0.075 mm for precision rolled strip. It is supplied in slit widths as specified by the customer, up to a maximum width of 2030 mm, depending on thickness. Material compatability of sheet, section and fixings is not always assured in practice due to commercial availability. F 4 Surface finishes F4.1 Stainless steel is available in a wide selection of finishes, varying from fine matt to mirror polished, as defined in BS 1449: Part 2: and in EN 10088: Part 2. Mill finishes Type 2D Cold finished softened and descaled. A uniform matt finish.

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Type 2B

Cold rolled, softened, descaled and lightly worked with polished rolls. A smooth finish brighter than 2D. Type 2A/2R Bright annealed. A cold finished reflective appearance retained through annealing. Polished finishes Type 4/2J Dull polished. A lustrous unidirectional finish produced by fine grinding, generally with abrasives of 150 grit size. It has little specular reflectivity. Further dull polishing after fabrication will diminish the effects on appearance of welds or accidental damage by blending them into the surrounding metal. Type 5/2K Dull polished with specific requirements, to achieve a fine, clean cut surface finish with good corrosion resistance. Type 8/2P Mirror polished. A bright, nondirectional reflective finish with a high degree of image clarity. F.4.2 Where other finishes are required, such as for aesthetic purposes, a range of patterned or textured (2F,2M) finishes is available. Colour may be applied in the form of paint or lacquer, or the material may be supplied pre-coloured as by the 'INCO' process or by mill application of polymer coatings. F.5 Surface protection F.5.1 No surface protection is required for stainless ductwork used indoors or outdoors, provided the correct quality is specified. This is because the naturally occurring chromium-rich oxide film which is present on the surface of the metal, if damaged, reforms immediately by reaction between the steel and the atmospheric or other source of oxygen. F.5.2 If a mixture of metals is used, such as mild steel supports for stainless steel ductwork, the surface of the mild steel must be adequately protected from the galvanic corrosion that might result from the intimate contact between the two types of metal. (The appropriate protective finish should be employed. See 27.3.5)

essary, however, depending on the type of stainless steel being used. F.6.3 As a general rule, the 400 series of stainless steels can be formed using normal mild steel settings. The 300 series, however, because of the higher yield point and the greater rate of work hardening, will require higher working pressures. F.6.4 Ductwork contractors who have experience of the use of stainless steel report difficulty in forming Pittsburgh and button punch snap lock seams. As regards cross joints, socket and spigot joints are recommended, and one or two of the slide-on flanges are suitable. In view of the foregoing, it is recommended that trials be carried out before starting on production. F.7 Rectangular ducts The constructional requirements for rectangular stainless steel ducts are the same as for galvanized mild steel. F.8 Circular ducts The constructional requirements for circular stainless steel ducts are the same as for galvanized mild steel. F.9 Stiffening Wherever possible, the material used for stiffening should be of the same grade of stainless steel as used for the construction of the ducts, or should be made equally corrosion resistant to suit the environment in which the ductwork is situated. F.10 Fixings and fastenings The types of fastening and the maximum spacings specified in Table 5 (rectangular) and Table 9 (circular) also apply to stainless steel ductwork. Fixings and fastenings should be of the appropriate grade of stainless steel as used in the construction of the ductwork, or should be made equally resistant to corrosion in relation to the environment in which the ductwork is situated. The type of stainless steel fastening used should conform to the appropriate specification BS 6105: 1981. F.11 Welding All the modern welding processes may be used to weld stainless steel but carburising operations such as oxyacetylene and carbon arc welding are not suitable. The Tungsten inert gas (TIG) and resistance welding techniques are most likely to be used for thin gauge materials. Attention is drawn to BS 4872: Part 1 1982, (welder qualification) and BS 7475: 1991 (welding processes). Selection of the correct welding electrodes and filler rods is important, particularly when welding dissimilar metals, such as stainless steels to non-stainless structural steels. Reference for guidance should be made to BS 2901: Part 2: 1990 for rods and wires for gas shielded welding and BS 2926:1984 for electrodes for Manual Metal Arc. (MMA) welding. F.12 Avoidance of contamination Attention is drawn to the risks of rust staining of stainless steel surfaces resulting from contamination by nonstainless steel or iron debris. 87

F.6 Construction F.6.1 Sheet thicknesses for stainless steel ductwork should be the same as for galvanized steel (see Tables 2, 3 and 4). Provided the correct grade of stainless steel has been selected, there is no requirement for a corrosion allowance with stainless steels and the gauge can be selected on structural considerations only. F.6.2 The forming of rectangular and circular ducts can be carried out by the use of conventional press working and sheet metal forming machines. Some alteration in working practices may be nec-

If particles such as filings of a non-stainless steel or iron are expressed into contact with a stainless steel, subsequent exposure to moisture will lead to staining of the surface as these particles rust. Whilst this staining often can be removed without harm to the stainless steel surface, in aggressive environments corrosion products around the rust centre can create a risk of pitting of the stainless steel. As a general rule, stainless steels should be kept free from iron dust and debris contamination. In particular, wire brushes must be made of stainless steel and shot, beads and abrasive media used to clean surfaces must be `iron free'. Contamination can arise from tools which have been used previously for cutting non-stainless steels without adequate cleaning and from abrasion on stillages and racks. It is good practice to dedicate storage and bench areas for stainless steels, with soft surfaces, e.g. wooden battens, to mininise scratching of the surface and if practicable designate stainless only working areas.

F.13 Fire dampers Stainless steel is an ideal material for use in the construction of fire dampers, because of its high resistance both to heat and corrosion. It is therefore most applicable where a fire authority specifies a requirement for corrosion resistance. F.14 Sealants, gaskets and tapes The sealing materials and methods set out in this publication are also applicable to stainless steel ductwork. However, any chloride-based material, such as polyvinyl chloride (PVC), should be avoided, as breakdown of such material at certain elevated temperatures could lead to corrosion of the stainless steel. F.15 General design considerations It is the designer's responsibility to indicate the type of stainless steel most suitable for the conditions to which the ductwork is to be exposed. If users and designers are in doubt as to which material is appropriate to a particular application, technical advice may be obtained from the source noted below.

Table 21, showing the approximate correspondence between the chemical compositions of the commonly used stainless steel grades in BS 1449, Part 2: 1983, and the European Standard EN 10088-1, List of Stainless Steels. (Part 1 gives the chemical compositions and identifications of the stainless steels, it is for information. Part 2 of this standard describes the technical delivery conditions for sheet/plate and strip for general purposes.)

This appendix is based largely on information kindly supplied by the Avesta Sheffield Technical Advisory Centre, ASTAC, P.O. Box 161, Shepcote Lane, Sheffield S9 l TR Telephone: 0114 244 0060 Fax: 0114-242 0162

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APPENDIX G - PRE-COATED STEEL

G.1 Nature of the material G.1.1 'Pre-coated' steel is sheet, coil or strip to which has been applied at the steel mills a coating having a decorative or protective function, or both. G.1.2 The basis metal to which the coatings are applied are hot-dip galvanized or aluminium-zinc coated sheet or coil, uncoated steel or electrogalvanized steel (e.g., Zintec). G.2 Range of coatings available G.2.1 A number of different types of coating, in various thicknesses, are available - PVC ('Plastisol' and 'Organosol'); paint coatings of several types, silicone enamels, etc. G.2.2 A wide range of colours and surface finishes are available, but there are minimum quantity requirements for some types of coating, finish and colour. The characteristics of the particular type of coating contemplated for a particular use should be investigated in respect of formability, fastness to light, chemical resistance and other relevant properties. G.2.3 The material can be supplied with one or both sides treated, with the specified coating. Standard `backing coat' finishes are usually applied to the reverse side unless otherwise stated. G.3 Sizes available G.3.1 Pre-coated steel is available in sheet or coil form. The maximum available width can vary according to the steel thickness required. Availability varies according to type of substrate and coating, so prospective purchasers should query the sizes available for the specific type required. G.4 Sources of supply G.4.1 Pre-coated steel is widely available but it should be noted that minimum order quantities may apply. G.5 Ductwork construction from pre-coated steel G.5.1 The type of pre-coated steel most suitable for ductwork should be carefully considered, mainly from the point of view of the fabrication properties of the coating type. It is probable that a plastisol coating will be found to be most suitable for ductwork, as this type of coating will withstand forming at normal ambient temperatures. It also tolerates rougher handling during forming and erection than the much thinner paint coating types. G.5.2 Careful consideration should be given to the constructional methods to be used for ductwork to be made from pre-coated steel. The principle to be followed should be to make seams and joints as unobtrusive as possible. Some of the conventional methods of seaming may be used, but a number of others are not suitable. Welding with conventional equipment should not be attempted. Mechanical fastenings should be chosen with care having regard to appearance as well as efficiency; and sealant should be applied with these factors in mind. Stiffening should be carefully considered in relation to appearance. G.6 Handling, storage, transport and erection G.6.1 Much more care than usual is required in these respects, as the coatings are all to a greater or lesser degree susceptible to mechanical damage. For example, sheet should not be dragged off the top of a pile but removed by `turning' off the stack. G.6.2 With sheet pre-coated on one side only, it may be found desirable to stack face to face. G.6.3 The flexibility of coatings of the types used on pre-coated steel depends on temperature. Therefore, manipulation should be carried out at temperatures above 16°C (60°F) in order to minimise the risk of the film cracking on roll forming, etc. If the material has been stored outside at low temperature, a warm-up period should be allowed before manipulation of the sheet is undertaken.

The information on which this appendix is based has been kindly supplied mainly by British Steel plc. More detailed information may be obtained from: British Steel plc, Product Development Centre, Shotton Works, Deeside, Flints CH5 2NH Telephone: Chester (01244) 812345 Fax: 01244 836134

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APPENDIX H - ALUMINIUM DUCTWORK

H.1 Scope This section applies only to rectangular and circular aluminium ductwork operating at low pressure, as defined in Tables 22 and 23. If consideration is being given to either higher pressures or flat oval ductwork then it would be prudent to seek advice from manufacturers who have the experience and capacity to manufacture aluminium ductwork. H.2 Suitable grades H.2.1 Ductwork can be constructed from all the commonly used aluminium alloys, the choice depending on the purpose for which the ducts will be used and the service environment. H.2.2 The alloys 1200, 3103 and 5251 (as specified in BS.EN485, BS.EN515, BS.EN573) are easy to form and to join, and have excellent resistance to atmospheric corrosion, with 5251 being rather more resistant to marine atmospheres. H.2.3 These alloys can be supplied in various tempers produced by different degrees of cold rolling, so that a range of strengths is available. In choosing a temper, it is necessary to consider any forming that will be done, as with the harder tempers the forming of tight bends might cause cracking. Where high strength is required, alloy 6082-T6 sheet can be used. H.2.4 Aluminium coil is available in plain form and prepainted finish. H.3 Construction - rectangular ducts H.3.1 Table 22 sets out the minimum constructional and stiffening requirements for rectangular aluminium ducts and the permitted types of cross joint. H.3.2 Sealant The sealant requirements set out in this specification for galvanized steel rectangular ductwork also apply to the longitudinal seams and cross joints in aluminium ductwork. H.4 Construction - circular ducts H.4.1 Table 23 sets out the minimum constructional and stiffening requirements for circular ducts made from aluminium, and the permitted types of cross joint. H.5 Fastenings H.5.1 The types of fastening and the maximum spacings specified in Table 5 (rectangular) and Table 9 (circular) apply to aluminium ductwork, except that such fastenings shall be of aluminium, stainless steel or monel metal. H.6 Welding H.6.1 All the aluminium alloys can be welded by MIG (Metal and Inert Gas) or TIG (Tungsten and Inert Gas) methods, with argon as the shielding gas. Helium or a mixture of helium and argon can be used, but not CO2. Alloys in a work-hardened temper are reduced to the annealed condition in the heat affected zone; 6082-T6 is reduced approximately from the T6 to the T4 temper. Alloys 1200 and 3103 are easy to braze, as is 6082, but the latter needs to be re-heat treated to regain its strength. H.7 Protective finishes H.7.1 No protective finishes are required for aluminium ductwork used indoors or outdoors in normal atmospheric conditions. In moist atmospheres, particularly if they are contaminated by industrial effluent or by salt from the sea, surfaces not exposed to washing by rain will become roughened and covered with a layer of white corrosion product. However, this has the effect of sealing the surface against further attack, and the mechanical properties of any but the thinnest of materials will be only slightly affected. H.7.2 If surface protection is specified, any of the normal organic finishes can be used, including the laminated PVC films, although paints with heavy metal pigments are not suitable. The use of prepainted strip in coil form provides a reliable quality finish and often proves more economical than painting after assembly. Anodising provides an excellent finish for aluminium, but this process would have to be carried out after forming and would therefore not usually be practicable for ductwork, except perhaps for ducts formed from extrusions. H.7.3 Mild steel section used in supporting aluminium ductwork shall have a protective finish (See 27.3.5)

90

Incorporates information provided by the Aluminium Federation Ltd., Broadway House, Calthorpe Road, Five Ways, Birmingham B15 1TN (telephone: 0121-456 1103), from whom more detailed information may be obtained.

APPENDIX J - EUROVENT

J.1 General Some explanation of the function, composition, objectives and membership of EUROVENT is given below. J.2 Membership EUROVENT is an omnibus word standing for the European Committee of the Construction of Air Handling Equipment. The committee was formed in 1959, and in 1977 its constituent members were the relevant national associations in Austria, Belgium, Denmark, Finland, France, German Federal Republic, Italy, Netherlands, Norway, Sweden, Switzerland and the United Kingdom. J.3 Objectives The objectives of EUROVENT are `to improve and develop technical matters in the manufacture and operation of air handling equipment; to improve the professional status of its members and to facilitate commercial exchanges between its member nations in the search for improved quality; and the adoption of rules, directives and codes of practice in the technical and economic spheres in the member countries'. J.4 EUROVENT publications EUROVENT has published a number of documents in the air handling field, and these include Document 2/2 covering the procedure for testing for air leakage in ductwork, and provides for two levels of permissible air leakage for low-pressure air distribution systems. Document 2/3 covers the standardisation of duct sizes. J.5 Air leakage The basis on which air leakage is calculated in EUROVENT Document 2/2 has been adopted in DW/143 A practical guide to Ductwork Leakage Testing.

Information about EUROVENT may be obtained from the HEVAC Association, Sterling House, 6 Furlong Road, Bourne End, Bucks SL8 5DG (Telephone: 01628 531186 Fax: 01628 810423)

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APPENDIX K - SUMMARY OF BS.EN10142: 1991 CONTINUOUSLY HOT DIP ZINC COATED MILD STEEL STRIP AND SHEET FOR COLD FORMING

Note - The extracts from BS.EN 10142: 1991 have been prepared by the HVCA and are included here by courtesy of the British Standards Institution. K.1 GENERAL K.1.1 The BS 2989: 1975 and 1982 entitled `Continuously hot-dip zinc coated and iron-zinc alloy coated steel: wide strip, sheet/plate and slit wide strip' summarised in DW/142 has been superseded by BS.EN10142: 1991 entitled `Continuously hot-dip zinc coated mild steel strip and sheet for cold forming' (including amendment A1:1995). K.1.2 British Standard BS.EN10142: 1991 sets out requirements for the conventional galvanized sheet and coil and for zinc-iron coated steel. (Both these are included in DW/144 - see Section 7.) The type of steel normally used for ductwork is DX51D and Z275. K.2 STEEL GRADES K.2.1 BS.EN10142: 1991 and the grades of steel set out in others: Grade Name of grade DX51D + Z Bending and profiling quality amendment A1:1995 lists the next column, among Application 1 Forming quality steel suitable for manufacture of the most profiles and more difficult bending operations Forming quality steel suitable for simple drawing operations and for more difficult profiling operations Forming quality steel suitable for deep drawing and difficult forming operations Forming quality steel suitable for deep drawing and difficult forming operations where a nonageing steel is required Normal spangle (N). This finish is obtained when the zinc coating is left to solidify normally. Either no spangle or zinc crystals of different sizes and brightness appear depending on the galvanizing conditions. The quality of the coating is not affected by this. NOTE. Normal spangle is the type normally supplied for a wide variety of applications. Minimized spangle (M). The surface has minimized spangles obtained by influencing the solidification process in a specific way. The finish may be specified if the normal spangle applicable does not satisfy the surface appearance requirements. K.5 SURFACE PROTECTION K.5.1 General Hot-dip zinc coated strip and sheet products generally receive surface protection at the producer's plant. The period of protection afforded depends on the atmospheric conditions. K.5.2 Chemical Passivation Chemical Passivation protects the surface against humidity and reduces the risk of formation of `white rust' during transportation and storage. Local discolouring as a result of this treatment is permissible and does not impair the quality. K.5.3 Oiling This treatment also reduces the risk of corrosion of the surface. It shall be possible to remove the oil layer with a suitable degreasing solvent which does not adversely affect the zinc. K.5.4 Chemical Passivation and Oiling Agreement may be reached with the producer on this combination of surface treatment if increased protection against the formation of `white rust' is required. K.5.5 Untreated Hot-dip zinc coated strip and sheet products complying with the requirements of this standard are only supplied without surface protection if expressly desired by the purchaser on his own responsibility. In this case, there is increased risk of corrosion. K.6 FORMING K.6.1 The British Standard says that provided that the profiling machine is set to avoid excessive stretching in the product, it is possible to form lock seams successfully with DX51 D + Z sheet up to a thickness of 1.5 mm and DX52D + Z sheet up to 2 mm; and snap lock seams with DX51 D + Z up to 0.9 mm thick sheet and DX52D + Z sheet up to 2 mm. K.7 WELDING K.7.1 Care should be taken to use proper methods and procedures. The iron-zinc coating is more suitable for resistance welding than the conventional zinc coating.

DX52D + Z Drawing quality

DX53D + Z Deep drawing quality

DX54D + Z Special deep drawing quality

K.3 COATING TYPES AND TOLERANCES K.3.1 The types of zinc coating are set out in Table 24. BS.EN10142: 1991 (reproduced at the foot of this summary). K.3.2 Whilst the coating thickness is not subject to tolerances the substrate and consequently the gauge thickness does have accepted tolerances and these including sheet widths/lengths will be found in BS.EN10143: 1991. K.4 COATING FINISHES K.4.1 BS.EN10142: 1991 and A1 1995 includes a description of the various types of finish available: 92

APPENDIX L -'DESIGN NOTES FOR DUCTWORK' (CIBSE Technical Memorandum No. 8)

L.1 At the time of publication (1983) this technical memorandum brought together information on the design of ductwork systems. L.2 The contents had been drawn from the relevant sections of the CIBSE Guide and other recognised references, and include additional material on good design practice. The Notes make frequent reference to DW/142, and an effort was made to ensure consistency between the two publications. Whilst DW/142 has now been superceded by DW/144, the technical memorandum, has not currently been updated but still contains relevant information that may be of use to a ductwork designer/manufacturer. Whilst some of the information may now be superceded, TM8 includes chapters on: Pressure loss in ducts, including corrections for duct surface type, air pressure, air density, temperature and altitude, and loss factors for fittings. Equivalent diameters of rectangular and flat oval ducts. Standard dimensions of circular, rectangular and flat oval ducts. Duct sizing methods, including velocity, equalfriction and static regain methods, and pressure loss calculations, with an example calculation. Heat loss from and gain to air in the duct; condensation, noise control and fire. Commissioning and testing. Overseas work. Drawing symbols in current use. L.3 The flow of heavily contaminated air in ducts is not covered in detail in the Notes; nor are the constructional aspects of ductwork, which are dealt with in DW/144. L.4. The Notes were completed by references, a bibliography of over thirty titles and appendices covering properties of air, ductwork support loads, velocity pressure for air flow and conversion to SI units.

Technical Memorandum No. 8 was published by the Chartered Institution of Building Services Engineers, Delta House, 222 Balham High Road, London SW12 9BS (Telephone: 0181 675 5211) and whilst it is no longer available as a publication, it is still available in photo-copy form.

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APPENDIX M - GUIDANCE NOTES FOR INSPECTION, SERVICING AND CLEANING ACCESS OPENINGS

M.1 GENERAL This appendix highlights, in summary form, the access consideration that should be made by the designer in terms of inspection, servicing and cleaning. Having considered the scope and the design of the ductwork system relative to the guidelines outlined below the designer should clearly indicate which levels of access should be incorporated into the manufacture of a new ductwork system (See Table 25 and Note 1 below it). M.2 DESIGN CONSIDERATIONS M.2.1 Inspection and servicing requirements are set out in Section 20 of this specification. M.2.2 Cleaning requirements are set out in the HVCA publication TR17 "Guide to Good Practice, Cleanliness of Ventilation Systems" and the guide states "The precise location, size and type of access would be dependent on the type of ductwork cleaning, inspection and testing methods to be adopted." Care, protection and standards of cleanliness prior to commissioning are set out in the HVCA publication DW/TM2 "Guide to Good Practice, Internal Cleanliness of New Ductwork Installations" and the guide states "Where specific limits of cleanliness are required, ductwork shall be cleaned after installation by a specialist cleaning contractor." It will be in the interests of the designer, both financially and practically, to consider employing a specialist cleaning contractor at the outset of a contract to internally clean newly installed ductwork prior to handover. This approach would realise the following benefits: i) The actual number of cleaning access panels could be determined to suit the method of cleaning to be adopted (This may be less than the maximum requirements listed under Level 3 of Table 25). ii) Clear directions could be given to the ductwork contractor as to the size and location of cleaning access panels that are required to be fitted during the manufacturing process. iii) The specialist cleaning operation prior to commissioning would enable the cleaning contractor to verify the practical access requirements for the future cleaning operations associated with a regular maintenance programme. iv) A specialist cleaning operation prior to commissioning would allow the designer to omit from the specification the DW/TM2 requirements for factory sealing, protection, wipe downs and capping-off. v) Specialist cleaning to the measurable standards defined in TR17 will allow an objective definition of cleanliness to be achieved. Careful consideration must be given by the designer to the practical problems associated with the manufacture and fitting of suitably sized access panels on small cross section ducts and the circular faces of round and flat oval ducts in particular. M.2.3 Special consideration must be given by the designer to the practical problems associated with gaining personnel access to heavily congested ceiling areas and multi-layered ductwork systems. This approach would avoid the possibility of access panels being incorporated into a ductwork system at the manufacturing stage that were later found in practice to be inaccessible for either servicing or cleaning activities. M.3 ACCESS TO IN-LINE EQUIPMENT This appendix only covers access/inspection through the ductwork body adjacent to an item of in-line equipment and not openings in the equipment itself.

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APPENDIX N - BIBLIOGRAPHY

Included in this Bibliography are technical publications which may be of interest to ductwork designers. fabricators and erectors, and to those in the heating, ventilating, air conditioning industries generally. Enquiries should be made of the relevant organisation, at the address quoted. Since its publication other addresses contained within DW/144 may have changed, and some publications may have been superseded. Research Reports RR01/95: Ventilation system hygiene - A review of published information on the occurrence and effects of contamination RR02/95: Air-to-air heat recovery RR03/95: Influence of HVAC on smoke detectors

HEATING AND VENTILATING CONTRACTORS' ASSOCIATION 34 Palace Court, London W2 4JG Telephone: 0171-229 2488; Fax: 0171-727 9268. Orders to HVCA Publications, Old Mansion House, Eamont Bridge, Penrith. Cumbria CA10 2BX (Telephone: 01768 864771 Fax: 01768 867138) Email: [email protected]

DW/144 DW/143 DW/151 DW/171 DW/191 DW/TM2 DW/TM3 Specification for sheet metal ductwork (low-, mediumand high-pressure) (1998) A practical guide to ductwork leakage testing (1983) Specification for plastics ductwork Guide to good Practice for kitchen ventilation systems Guide to good practice glass fibre ductwork DWITM1 Acceptance scheme for new products -Rectangular cross joint classification Guide to good practice - Internal cleanliness of new ductwork installations Guide to good practice for the design for the Installation of fire and smoke dampers

NATIONAL ENGINEERING SPECIFICATION LIMITED Southgate Chambers, 37/39 Southgate Street, Winchester S023 9EH (Telephone: 01962 842058; Fax: 01962 868982) BUILDING SERVICES RESEARCH AND INFORMATION ASSOCIATION Old Bracknell Lane West, Bracknell, Berkshire RG12 4AH (Telephone: Bracknell (01344) 426511; Fax: 01344 487575)

Application Guides AG.1/74 Designing Variable Volume Systems for Room Air Movement AG.I/91 Commissioning of VAV Systems in Buildings. TN.6/94 Fire Dampers LB.65/94 Ventilation of Kitchens AG.3/89 The Commissioning of Air Systems in Buildings AH.2/92 Commissioning of Bems - A Code of Practice TN.24/71 Fire Dampers in Ventilating Ducts.

Other publications JSI H&V safety guide 5th edition JS2 Tool box talks JS5 Welding Safety booklet JS19 Safety facts booklet. Fact sheets 1-24 2nd edition JS21 COSHH manual volume I Advice on compliance with the regulations JS 21A COSHH manual volume 2 Assessment sheets JS23 Risk management manual TR/3 Brazing and bronze welding of copper pipework and sheet(1976) TR5 Welding of carbon steel pipework (1980) TR6 Guide to Good Practice for Site Pressure Testing of Pipework (1980) TR17 Guide to good practice cleanliness of ventilation systems.

HEATING, VENTILATING AND AIR CONDITIONING MANUFACTURERS ASSOCIATION (HEVAC) Sterling House, 6 Furlong Road, Bourne End, Bucks SL8 5DG (Telephone: 01628 531186 Fax: 01628 810423 Email: [email protected])

Publications Air Diffusion Guide Guide to Air Handling Unit Leakage Testing Guide to Good Practice: Air Handling Units Real Room Acoustic Test Procedure Specification for the Certification of Air Filters Method of Test for Water Rejection Performance of Louvres Subjected to Simulated Rainfall Test Procedure for Acoustic Louvres Specification for Floor Grilles - Types, Performance and Method of Test Specification for the Determination of the Collection Efficiency of Sand Trap Louvres Domestic Mechanical Ventilation Systems with Heat Recovery Fan Application Guide Fan and Ductwork Installation Guide Guide to Fan Noise and Vibration Specification of Requirements for Natural Smoke and Heat Exhaust Ventilators Specification for Powered Smoke and Heat Exhaust Ventilators Specification of Requirements for Smoke Curtains Design Guide of Smoke Ventilation for Single Storey Industrial Buildings Including those with Mezzanine Floors and High Racked Storage Warehouses - Issue 3 Guidance for the Design of Smoke Ventilation Systems for Covered and Underground Car Parks - Issue 1 Application of Smoke Control Equipment and Systems: Guide to Good Practice - Issue 1

CHARTERED INSTITUTION OF BUILDING SERVICES ENGINEERS Delta House, 222 Balham High Road; London SW12 9BS (Telephone: 0181-675 5211 Fax: 0181-675 5449)

CIBSE Guide Volume A Design Data Volume B Installation and Equipment Data Volume C Reference Data Commissioning Codes These Codes cover the preliminary checks, setting to work and regulation of various categories of plant. The Codes give a guide to design implications. Series A Air Distribution Systems Series B Boiler Plant Series C Automatic Control Systems Series R Refrigerating Systems Series W Water Distribution Systems Technical Memoranda TM 4 Design Notes for the Middle East TM 8 Design Notes for Ductwork TM 13 Minimising the Risk of Legionnaires Disease

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BRITISH STANDARDS INSTITUTION Sales Department, 101 Pentonville Road, London N1 9ND (Telephone: 0171-837 8801)

BS 381 C: 1996 CP 413: 1973 BS 476: Part 4: 1984 Part 6: 1989 Part 7: 1993 Part 20:1987 Part 21:1987 Part 22:1987 Part 23:1987 Part 24:1987 BS 5588 Part 9:1980 BS 729: 1971 BS 1449: Part 1:1991 Part 2:1983 and BS.EN 10149-2: 1996 BS.EN 10149-3: 1996 BS.EN 10131: 1992 BS.EN485 Parts 1-4 BS.EN515 1993 BS.EN573 Parts 1-4 BS 1474:1972 and BS.EN755 Parts 3-6 BS.EN22063: 1994 Sprayed metal coatings Protection of iron and steel by aluminium and zinc against atmospheric corrosion Protection of iron and steel against corrosion and oxidation at elevated temperatures Continuously hot-dip zinc coated mild steel strip and sheet for cold forming - technical delivery conditions Continuously hot-dip zinc coated and ironzinc alloy coated steel sheet and strip tolerances on dimensions and shade Glossary of terms relating to thermal insulation Self-tapping screws and metallic drive screws Wrought aluminium and aluminium alloys bars, tubes and sections Wrought aluminium and aluminium alloys for general engineering purposes - plate, sheet and strip. Fire Precautions in the design and construction of buildings Hot dip galvanized coatings for iron and steel articles Steel plate, sheet and strip Carbon steel plate, sheet and strip Stainless steel plate, sheet and strip. Colours (of ready-mixed paints) for specific purposes Ducts for building services Fire tests on building materials and structures Non-combustibility test for materials Fire propagation test for materials Surface spread of flame tests for materials Fire resistance of elements of construction Fire resistance of loadbearing elements of construction Fire resistance of non-loadbearing elements of construction Contribution of components resistance of a structure Fire resistance of ventilation ducts to the fire

SHEET METAL AND AIR CONDITIONING CONTRACTORS' NATIONAL ASSOCIATION INC. (SMACNA) Headquarters: 4201 Lafayette Center Drive Chantilly Virginia 20151-1209 Mailing Address P.O. Box 221230 Chantilly Virginia 20153-1230 Telephone (703) 803-2980 Fax (703) 803-3732

Accepted Industry Practice for Industrial Duct Construction (1975) Architectural Sheet Metal Manual (1993) Contractors Guide for Modification to Construction Contracts (1993) Ducted Electric Heat Guide for Air Handling Systems (1994) Energy Conservation Guidelines (1984) Energy Recovery Equipment & Systems (1991) Fibrous Glass Duct Construction Standards (1992) Fire, Smoke & Radiation Damper Install. Guide for HVAC Systems (1992) Guide to Steel Stack (1995) HVAC Air Duct Leakage Test Manual (1985) HVAC Commissioning Manual (1994) HVAC Duct Construction Standards-Metal & Flexible (1995) Addendum No. I (Nov 1997) HVAC Duct Systems Inspection Guide (1989) HVAC Systems-Application (1986) HVAC Systems-Duct Design (1990) HVAC Systems-Testing, Adjusting & Balancing (1993) Indoor Air Quality Manual (1993) Kitchen Equipment Fabrication Guidelines (1990) Managers' Guide for Welding (1993) Rectangular Industrial Duct Construction Standards (1980) Round Industrial Duct Construction Standards (1977) Seismic Restraint Manual (1991) (w/ Appendix E, 1993) SMACNA Master Index of Technical Publications (1995) Thermoplastic Duct (PVC) Construction Manual (1994)

BS.EN10142: 1991 BS.EN10143: 1991 BS 3533: 1981 BS.EN.ISO: 1479 BS.EN.ISO: 7049: 1994 BS 4800:1989 BS 4848: Part4: 1972 BS 5422:1990 BS 5720: 1979 BS 5970: 1992

DEPARTMENT OF THE ENVIRONMENT (Publications Centre) H.M. Stationery Office, 51 Nine Elms Lane, London SW8 5DR

M & E No.1 1972 M & E No.3 1988 M & E No.4 1970 Electrical installations in buildings (New Edition) Heating, hot and cold water, steam and gas installations for buildings Central heating and hot and cold water installations for dwellings

M & E No.1001971 Mechanical ventilation for buildings

Paint colours for building purposes Hot rolled structural steel sections Equal and unequal angles Specification for the use of thermal insulating materials Code of practice for mechanical ventilating and air conditioning in buildings Code of practice for thermal insulation of pipework

BRITISH STEEL PLC Market Communications Dept British Steel PLC Strip Products P.O. Box 10 Newport South Wales NP9 OXN (Telephone 01633 290022) (Fax 01633 464087)

Publication: Edge protection by zinc

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ASSOCIATION FOR SPECIALIST FIRE PROTECTION Association House 235 Ash Road Aldershot Hampshire GU 12 4DD Telephone 01252 21322 Fax 01252 333901 Publications. Fire Rated and Smoke Outlet Ductwork: An Industry Guide to Design and Installation.

HEALTH AND SAFETY EXECUTIVE Rose Court 2 Southwark Bridge London SE1 9HS Telephone 0171-717 6000

APPENDIX P - CONVERSION TABLES Sheet thicknesses

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98

NOTES

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NOTES

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101

Information

Specification for Sheet Metal Ductwork

102 pages

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