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Heat Recovery Steam Generator (HRSG) Technology

One-Day Training

Workshop (10 November 2003)

&

Two-Day Conference (11 - 12 November 2003)

Venue: Woburn House*, London, UK

(Central London)

Dates: 10 - 12 November 2003

Expanded PROGRAMME & Abstracts + Registration Form

Organiser

European Technology Development (ETD) Sponsors

SES

Stress Engineering Services (Europe) Ltd * Venue: Woburn House, 20 Tavistock Square. London WC1H 9HQ.

Location of Woburn House can be found at: http://www.universitiesuk.ac.uk/facilities/ Nearest train stations: Euston / Kings Cross Nearest Underground train stations: Euston, Euston Square, Kings Cross, Russell Square.

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INTRODUCTION This first Training Workshop and International Conference on HRSG Technology will comprehensively review recent advances in the design, operation, maintenance, and construction of steam systems in combined cycle gas turbine (CCGT) plant. The need for such a forum comes from the shift to higher temperatures and pressures in HRSG units, which gives opportunities and challenges in terms of innovative designs, choice of materials (e.g. P22 or P91), control systems and water treatment. The complexity of design and operating decisions has been intensified by the need for HRSG units to load cycle and two-shift. Furthermore, although new HRSG systems are being designed with plant cycling in mind, there are many older units that can benefit from improved operating techniques. With these older units, life assessment procedures are needed to assess long term damage from cyclic operation and for optimised selection of maintenance practices. The two-day Conference, following the Training Workshop, consists of presentations from manufacturing and design organisations, plant operators and companies which supply ancillary equipment and services. Since the provisional programme was announced earlier this year (2003), a number of additional papers have been offered to include design and operational aspects of HRSG systems and this has led to the expansion of the original programme, hence the issue of this revised programme. In addition short abstracts for the individual papers are attached to the programme. The schedule for the Training Workshop remains as before. The Conference is being preceded by an optional one-day Training Workshop which comprises lectures and discussions on HRSG design and thermodynamics, HRSG heat transfer, materials of construction, operating considerations, failure mechanisms etc. The Workshop will, therefore, be an excellent introduction to the formal reviews of innovations in HRSG construction, materials technology and operation, to be presented, over the following two days, at the Conference itself. ABOUT THE ORGANISER European Technology Development Ltd. (ETD) is a UK based engineering advisory, consulting and R&D company specialising in life assessment/extension, maintenance, materials and engineering issues in all type of power generating plant. The company has a particular interest and expertise in the growing areas of CCGTs and HRSGs. The company has in the recent past organised various international conferences and training workshops / courses in the UK and other countries (Germany, France, Portugal, Hong Kong, Malaysia etc.) mainly on the issues such as: high temperature materials, welds, component safety and durability, weld repairs, power plant cycling and RBM (Risk Based Management). The company provides specialist services in Asset Integrity (stress analysis, defect assessment, remaining life assessment etc.), Risk Based Management / Maintenance, Advisory Services in Materials Selection / Welding Repair, and Training Courses in Plant Integrity and Life Assessment. ETD is also involved in leading edge large multimillion euro `technology development' projects in the above and related areas. This high tech knowledge base gives ETD a specialist advantage in providing services and training to plant manufacturers / designers and operators. More information about the company, its projects and activities can be visited at: www.etd1.co.uk

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TRAINING WORKSHOP

Monday 10 Nov. 2003

The Training Workshop comprises lectures and discussions on the basics of the design, operation, maintenance and construction of steam raising plant in CCGT systems and the background to more recent innovations and developments. The Workshop should be of particular interest to plant operators, service providers, researchers, plant manufacturers and designers. The Workshop will be useful as a stand-alone event but will also provide an excellent foundation for further discussion of these issues during the Conference. Experts in key technical areas will lecture and lead discussions. Each lecture will be of one hour duration followed by 15 minutes of discussion. =============== The Workshop Programme is as follows:

Registration ­ 0830 ­ 0900 Hours

Lecture 1: CCGT Thermodynamics and Implications for Heat Transfer (F Starr, European Technology Development, UK) Optimisation of pressure ratio and temperature for gas turbines. The pinch point concept. Implications for reheating and feedheating. Excess air ratios. In-duct burning. Stack gas and feedwater temperatures. (0900 ­ 1015 hrs)

Break ­ 1015 ­ 1030 hours

Lecture 2: Typical CCGT Plant Layouts and Implications for HRSG Design and Operation (P Fontaine, Cockerill Mechanical Industries, Belgium) HRSG/Gas Turbine combinations. Horizontal and vertical duct systems. Natural versus forced circulation. Drum boiler and once-through systems. Ductwork, support and expansion arrangements. Silencing and NOx control. Control systems. (1030 - 1145 hrs)

LUNCH

1145 ­ 1300 Hours

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Lecture 3: HRSG Heat Transfer Basics (G Sorbie, Scottish & Southern Energy, UK) Flue gas side heat transfer. Water and steam side heat transfer. Two phase flow. Design implications for heat transfer and condensate removal. (1300 ­ 1415 hrs)

Break ­ 1415 ­ 1430 hours

Lecture 4: HRSG pressure parts construction and CCGT unit operation during startups and shutdowns (M Pearson, J Michael Pearson & Associates Co. Ltd., Ontario, Canada) Alternative HRSG tube and header arrangements and their suitability for two-shifting. Implications on life of header/manifold thickness. Causes of localized high stresses in pressure parts during start ups and shut downs. Influence of combustion turbine exhaust gas characteristics during CCGT start up and shut downs on HRSG life. Influence of design and operation of key HRSG and BOP auxiliaries on HRSG damage. Potential tube/header failure mechanisms including thermal-fatigue, creep fatigue, corrosion fatigue, overheating. (1430 ­ 1545 hrs)

Break - 1545 ­ 1615 hours

Lecture 5: HRSG Materials, Fabrication Processes, Corrosion Mechanisms and Chemistry (A Fleming, European Technology Development, UK) Typical materials of construction, metallurgical background, welding and recent developments. Manufacture of finned tubes. Pre-operational cleaning. Water/steam side and gas side corrosion mechanisms and causes. Alternative water chemistry treatment methods. HRSG lay-up procedures. (1615 ­ 1730 hrs)

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CONFERENCE

11 - 12 Nov. 2003

This two-day International Conference will provide a forum for constructors and fabricators to review the latest innovations and insights into HRSG boiler and superheater design. It will also give an opportunity for operators, maintenance and inspection organisations to identify key issues with respect to operability and reliability. In short, the intention is to highlight improvements in HRSG mainstream and supporting technologies, and to single out areas where improved operating procedures are both necessary and practical. As noted earlier, because of the wide range of subjects covered, the Conference will be preceded with a one-day Training Workshop on HRSG Technology, which although not mandatory, delegates are encouraged to attend, especially those new to recent developments in HRSG systems technology.

Tuesday 11th November 2003

REGISTRATION AND COFFEE Introduction and Welcome Ahmed Shibli, European Technology Development Ltd., UK (0830 ­ 0935 hours)

(0935 ­ 0940)

Session 1: HRSG DESIGN, CONSTRUCTION AND FUTURE PROSPECTS (0940 ­ 1200 Hours) Chairperson: Fred Starr, ETD Keynote Paper: HRSG Dependability B Dooley, EPRI; S Paterson, Aptech, USA; M. Pearson, Pearson Associates, Canada (0940 ­ 1020 h) Latest trend in Improving the Constructability of HRSGs Glenn Selby, Alstom Power, Winsor, CT, USA (1020 ­ 1045 h) Status of HRSG Design, Construction and Future Prospects T Van Manen, NEM, The Netherlands

(1045 ­ 1110 h)

Comparison of Various Tube to Header Attachment Details Under Cyclic Service Lewis Douglas, Nooter Eriksen Inc, USA (1110 ­ 1135 h) Cycling Tolerance - Natural Circulation Vertical HRSGs P Fontaine, Cockerill Mechanical Industries, Belgium LUNCH BREAK -------------------

(1135 ­ 1200 h)

1200 ­ 1300 Hours

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Session 2: DESIGN AND EXPERIENCE WITH CYCLIC OPERATION (1300 ­ 1430 Hours)

Keynote Paper: Understanding the Design and Operational Parameters that Lead to Long Life of HRSGs in Cycling Duty Thomas Mastronarde, Chief Engineer, Ian Perrin, Technology Manager, Alstom Power, Winsor CT, USA (1300 ­ 1340 h) Influence of HRSG and CCGT Plant Design and Operation on the Durability of Two-Shifted HRSGs Michael Pearson, J Michael Pearson & Associates Co. Ltd, Ontario, Canada Robert Anderson, Founder/Chairman of USA HRSG User Group; Combined Cycle Systems Manager, Progress Energy, USA (1340 ­ 1405 h) The Safety, Economic and Technical Considerations for Multiple Shift Operation of HRSG Plants (1405 ­ 1430 h) C Dometakis, ERA Technology, UK

COFFEE BREAK

-------

1430 ­ 1450 Hours

SESSION 3: PRACTICAL MAINTENANCE AND REPAIR

EXPERIENCE WITH OPERATION, (1450 ­ 1615Hours )

Keynote Paper Managing HRSG Integrity and Reliability in Today's Power Market D Spalding, Business Development Manager - Utility and Industrial Improvements, Mitsui Babcock Technology Centre, Mitsui Babcock Energy, Renfrew, UK (1450 ­ 1525 h) Maintenance Free HRSGs ­ A User's View T Itay, E. Rindenau and D Laredo, Israel Electricity Company, Israel (1525 ­ 1550 h) Tracing an HRSG Vibration Problem Back to Source John M Brear and Paul Jarvis, Stress Engineering Services (Europe), UK (1550 ­ 1615 h)

COFFEE BREAK

-------

1615 ­ 1630 Hours

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SESSION 4: WELDING AND WELD REPAIRS OF HRSG EQUIPMENT (1630 ­1800 Hours)

Keynote Paper: Use of P91 in HRSG Construction and Weld Repair Issues A Fleming, I A Shibli, European Technology Development, Surrey, UK (1630 ­ 1710 h) Field Welding of P91 J F.Henry and T J Bary, Alstom Power, Winsor CT, USA (1710 ­ 1735 h)

The use of Induction Heating in the Welding of HRSG Components Gary Lewis, Miller Welding USA (1735 ­ 1800)

Conference Dinner & Boat Trip on River Thames

1930 ­ 2230 Hours

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Wednesday 12th November 2003

SESSION 5: WATER TREATMENT AND CORROSION ISSUES (0900 ­ 1055 Hours)

Keynote Paper Operational Chemistry Experience for the Control of Corrosion Risks in Heat Recovery Steam Generators Geoff Bignold, Innogy, Windmill Hill Business Park, Swindon, UK (0900 ­ 0940 h) GESM Water Treatment for HRSGs Steve Hughes, Alan Promfret, G E Water Technologies, N. Ireland, UK (0940 ­ 1005 h) Flow Assisted Corrosion in HRSGs Frank Gabrielli, Technical Fellow, Corrosion and Chemical Technology, Alstom Power, Winsor CT, USA (1005 ­ 1030 h)

Experience with Failure Mechanisms in the Water Steam System of HRSG Units A G L Zeijsseink, E. Mueller, R. Heijboer, KEMA, The Netherlands (1030 ­ 1055 h)

COFFEE BREAK -------

1055 ­ 1115

SESSION 6: BURNER AND HEAT TRANSFER ISSUES (1115 ­ 1245 Hours) Remedial Activities Carried Out on the Fawley Co-Generation Plant HRSG to Overcome Evaporator Dryout and Forced Draft Air Distribution Problems Roger Allan, Corporate Engineer, Boiler Performance: Innogy Plc, Swindon, UK (1115 ­ 1155 h) Fin Design, Fabrication and Heat Transfer Enhancement in HRSG Boilers P.Boone, Rosink Apprate-und Anlagenbau GmbH, Nordhorn, Germany (1155 ­ 1220 h) Operating Experience in High Supplementary Fired HRSGs for Co-Generation Plant G Viswanathan, T Balakrishnan, S Sundaresan, Baharat Heavy Electrical Ltd., India (1220 - 1245 h) LUNCH BREAK ------------------1245 ­ 1345 Hours

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SESSION 7: INSPECTION, MONITORING AND LIFE MANAGEMENT (1345 ­ 1500 Hours) New Italian Legislation for Pressure Equipment Design and HRSG Experience A Tonti, C Dell Site, ISPESL, Italy (1345 ­ 1410 h) Practical Approach to HRSG Life Management A Jones, Powergen, UK

(1410 ­ 1435 h)

CCGT Modelling as a Tool for Condition Monitoring T al-Shemmeri, Staffordshire University; S. Pace, Connah's Quay CCGT Plant, UK (1435 ­ 1500 h)

PANEL DISCUSSION ON CCGT DESIGN AND OPERATION ISSUES (1500 ­ 1530 Hours)

===========================================================

Technical enquiries to: Mr F Starr, Conference Chairman European Technology Development Ltd., 2 Warwick Gardens, Ashtead, Surrey KT21 2HR, UK. Tel: +44 (0) 208 764 7837 (direct) or +44 (0) 1372 802 555 Fax: +44 1372 229 164 E.mail: [email protected] or [email protected]

Publication: Copies of the Presentations and Papers will be provided at the Seminar.

EXHIBITION:

contact:

For exhibition of your products please

[email protected] Tel: + 44 (0) 1372 802 555 Fax: + 44 1372 229 164

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Registration Form

Please copy and post / fax / e-mail completed Form to the Registration Address shown at the bottom. Training Workshop + International Conference on Heat Recovery Steam Generator (HRSG) Technology, 10 - 12 November 2003, Woburn House, London, UK Registration Fee For the events held in the UK, overseas delegates also need to pay UK applicable `value added tax' (VAT) @ 17.5%. All figures are in UK pounds.

Until 6th October 03 Amount payable (Fee + VAT) £ 353 £ 647 £ 588 £ 882 After 6th October 03 Fee Amount payable ** (Fee + VAT) 350 £ 412 600 £ 705 500 £ 588 800 £940

Fee Workshop Conf. Workshop + Conf. Delegate Author All 300 550 500 750

**

** Please put a cross in the appropriate box. Registration Fee covers Conference Proceedings, coffee, lunches and Conference Dinner. Payment: Fee to be paid into the UK pound sterling bank account: A/c Name: European Technology Development Ltd., Bank: Nat West Bank, A/C No: 26096625, Sort Code: 60-12-36. Please quote reference: `HRSG Technology' Credit Card Payment Payment can also be made using Visa, Mastercard, Switch, JCB etc. (except American Express and Diners Club). Please provide, by fax / post credit card number, expiry date and name of the account holder. ------------------------------------------------------------------------------------------------------Information on hotel reservation will be provided on registration.

---------------------------------------------------------------------------------------------------------------Information below is required for your badge:

Your title and name: Company: Position: Address: Phone: Fax: E-mail:

Please state how and when the Registration Fee was paid or will be paid: ............... ....................................................................................................... Registration Section, ETD Ltd., 2 Warwick Gardens, Ashtead, Surrey KT21 2HR, UK Tel: + 44 (0)1372 802 555, or + 44(0)1372 229 162 Fax: +44(0)1372 229 164 E.mail: [email protected]

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ABSTRACTS

Tuesday 11th November 2003

HRSG Dependability: B Dooley, EPRI; S Paterson, Aptech, USA; M. Pearson, Pearson Associates, Canada Heat Recovery Steam Generator (HRSG) dependability relates strongly to the original design, thermal transients experienced, and the cycle chemistry regimes chosen. Main types of HRSG tube failures are: corrosion fatigue in economizers and evaporators, thermal fatigue in economizers, superheaters and reheaters, flowaccelerated corrosion (FAC) in low pressure evaporators, and under-deposit corrosion (hydrogen damage, acid phosphate corrosion, and caustic gouging) in high pressure evaporators. The paper will review some of the most important HTF mechanisms, the optimum approach to choosing the chemistry for each pressure cycle, and the key thermal transient issues and solutions. Latest trend in Improving the Constructability of HRSGs: Glenn Selby, Alstom Power USA and Carlo Accornero Alstom Power Italy This paper will describe the latest trends in methods to improve the constructablity of HRSGs and provide some of the design limitations of designing an HRSG so that field labour hours are minimized. Status of HRSG Design, Construction and Future Prospects: T Van Manen, NEM, The Netherlands The paper assesses the issues in determining which is best for cycling operation, the vertical or the horizontal design of HRSG? In theory, the vertical HRSG is more suitable to operate as a cycling unit. However, the horizontal HRSG can be designed to be just as effective for cycling operation. A considered view is that when the two types are critically reviewed the final conclusion must be that both types of HRSGs will face the same operationally derived problems during cyclic operation. Other differences between the two types will be discussed as well Comparison of Various Tube to Header Attachment Details Under Cyclic Service: Lewis Douglas, Nooter Eriksen Inc, USA The stresses in three different tube-to-header HRSG connections are analysed for cold warm and hot start cycles, using three dimensional finite element analysis. The types of weld geometries were (a) full penetration set-on detail (b) partial penetration stick-through detail and (c) full penetration butt weld to extruded opening. The results indicate that the highest stresses are found away from the tube to header welded area. For the individual start up schedules equations are given for estimates of the number of cycles to failure are given. Cycling Tolerance - Natural Circulation Vertical HRSGs: P Fontaine, Cockerill Mechanical Industries, Belgium Deregulation in the USA is having a serious impact on the design of HRSGs. Plants sizes are much bigger and many of them are now needing to cycle. This type of daily operation with big plants has been common in some parts of Europe for more than two decades. This paper looks at the design details of modern vertical HRSGs, including serpentine tube arrangement, tube diameter, finning and partial versus full

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penetration welding. Modern designs are also able to dispense with forced circulation, which was previously considered mandatory for vertical type HRSGs. Understanding the Design and Operational Parameters that Lead to Long Life of HRSGs in Cycling Duty: Thomas Mastronarde, Chief Engineer, Ian Perrin, Technology Manager, Alstom Power, Winsor CT, USA HRSGs are increasingly required to endure significant cyclic operation. To quantify the significance of some of the postulated failure scenarios, Alstom Power instituted a program of monitoring transient and steady state process conditions and metal temperatures to support finite element modelling to evaluate the life of critical components. Components instrumented include the tubes and headers of highpressure superheaters, superheater and reheater manifolds, economizer tubes, and headers and connecting links and support hangers. Detailed finite element models have been constructed for components shown to experience the most severe temperature transients. Monitoring data has been used to derive realistic thermal boundary conditions. Suitable material models and life assessment methods have been selected to compute the cyclic life. The analyses demonstrate that the cyclic durability of components is controlled both by the nature of the transients to which they are subjected and by component design, which encompasses both local geometric details and global flexibility of entire assemblies. Influence of HRSG and CCGT Plant Design and Operation on the Durability of Two-Shifted HRSGs: Michael Pearson, J Michael Pearson & Associates Co. Ltd, Ontario, Canada Robert Anderson, Founder/Chairman of USA HRSG User Group; Combined Cycle Systems Manager, Progress Energy, USA The durability of HRSGs in two-shifted cyclic service is significantly influenced by a few key HRSG design, combustion turbine control, balance-of-plant design and combined cycle unit operation choices. The main focus of the paper is the effect of changes in the operation of a Frame 7FA gas turbine on the life of critical sections of an HRSG such as the toe of the weld in tube to header connections. Significant reductions in fatigue damage can be achieved in existing plants by altering combustion turbine control characteristics and combined cycle unit operating procedures. The Safety, Economic and Technical Considerations for Multiple Shift Operation of HRSG Plants: C Dometakis and R. Cotgrove ERA Technology, UK Experience on base load plant has shown that their reliability and availability is already threatened by the vulnerability of some HRSG designs to unplanned thermal fatigue cycles caused by higher than anticipated trip rates. Although a change to multiple shift operation may be essential for the immediate economic survival of the power producer, it is necessary to assess the safety and economic risks that arise over the lifetime of the plant and what actions are necessary to ensure safe and viable operation. Managing HRSG Integrity and Reliability in Today's Power Market: D. Spalding Mitsui Babcock UK It is widely recognised that the UK power generation industry is facing significant challenges since the introduction of NETA and the reduction in wholesale prices for electricity. The profitability of generating plants is being severely squeezed and to

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meet variable demand, plants are being forced to operate outside the envelope for which they were originally designed. As a result there is an increase in plant defects and failures. Mitsui Babcock, as a supplier of engineering upgrade, repair and maintenance services has seen the impact of reduced expenditure and the consequences of operators not investing sufficiently in plant improvements to facilitate cyclic operation. This paper summarises the problems that have been predicted and more importantly those, which have emerged, and indicates the relatively inexpensive means by which these could be avoided. Maintenance Free HRSGs ­ A User's View :T Itay, E. Rindenau and D Laredo, Israel Electricity Company, Israel Weld defects, that are very rare in boilers in general, can be very detrimental to the compact maintenance free designed HRSG. The access to the failed welds is, in general, extremely difficult. This disadvantage leads to extended repair periods and to the unnecessary cutting of sound tubes, which prevent access. This paper deals with an uncertainty situation: Are there likely to be weld defects in HRSG components and how many are there and where? Issues of this type could occur during on-site construction of the HRSG where quality control was not appropriately conducted or supervised and the inspection techniques not clearly specified The paper deals with the "Maintainability Concept" which appears to be the most effective approach to prevent embedded human error risks. Tracing an HRSG Vibration Problem Back to Source: John M Brear and Paul Jarvis, Stress Engineering Services (Europe), UK Problems were encountered during the commissioning of a single-shaft, combined cycle unit in that significant erratic movements were observed on certain HRSG manifolds as the power was increased. These movements were sufficient to prevent continuous operation at full power without fear of impending failure or danger and had therefore delayed commissioning and handover. This paper describes the investigation of the problem and the solution reached. Use of P91 in HRSG Construction and Weld Repair Issues A Fleming, I A Shibli, European Technology Development, Surrey, UK The 9Cr martensitic steel series have been in use, in a number of conventional pf plants, since the late eighties / early nineties and there have been a few instances of P91 failures. P91 is now being specified in CCGT plant in the HRSG sections. The paper reviews the main problems with P91 use in thick section (headers) and thin section (heat transfer tubing) components and the likely impact on HRSG plant. It identifies repair problems, such as the high PWHT temperatures required, and reviews the state of the art in the development of weld repair techniques for P91. Field Welding of P91: J F. Henry and T J Bary, Alstom Power, Winsor CT, USA Compared to steels like P22, P91 has a much lower tolerance for deviations and it is important to carefully follow established procedures for post weld heat treatment (PWHT). While shop conditions can be closely monitored and controlled, field conditions present unique challenges. This paper will explain the importance of, and make recommendations for, the monitoring and controlling of welding electrode chemistry; preheat, interpass and PWHT of the weldment, as well as provide recommendations for minimizing the introduction of excessive mechanical stresses into the weldments.

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Wednesday 12th November 2003

Operational Chemistry Experience for the Control of Corrosion Risks in Heat Recovery Steam Generators: Geoff Bignold, Innogy, Swindon, UK Many CCGT plants that were set up for base load operation are now operating much more flexibly and this gives rise to additional concerns for the plant chemist. Control of dissolved oxygen and other potentially corrosive contaminants becomes more challenging. Risks of corrosion damage arising from deviations in hydrodynamic conditions have potentially serious implications for plant life. Chemical conditions that would have been acceptable in the absence of hydrodynamic irregularities can become unacceptably corrosive in their presence. However, appropriate choice of materials and selection of chemistry options can reduce the risks. Case histories are reviewed and options for prevention of future corrosion damage are discussed. GESM Water Treatment for HRSGs: Steve Hughes, Alan Promfret, G E Water Technologies, N. Ireland, UK This paper covers all aspects of water treatment of HRSG systems including procedures to be adopted during boiler commissioning as well as normal operations. In particular it summarises the merits of the different types of boiler water conditioning systems for both once through and drum type systems. Flow Assisted Corrosion in HRSGs: Frank Gabrielli, Technical Fellow, Corrosion and

Chemical Technology, Alstom Power, Winsor CT, USA

The causes of FAC are discussed and its specific relationship to the water chemistry in combined cycles. It will identify those areas of the HRSG where fluid temperatures and turbulent conditions provide a local environment, which is inherently susceptible to FAC under adverse water chemistry conditions. Field experiences and cases of FAC damage will be reviewed. FAC can be prevented by appropriate feedwater and boiler water chemistry. Alternative solutions such as the use of low chromium alloys in strategic areas as well as inspection issues are also discussed. Experience with Failure Mechanisms in the Water Steam System of HRSG Units: A G L Zeijsseink, E. Mueller, R. Heijboer, KEMA, The Netherlands Combined cycle units in the Netherlands vary a lot in size and design; from "simple" single pressure units less than 100 MW to "big" 350 MW units with multi-pressure stage designs. Yearly operational hours vary from peak load units to base load. The availability and efficiency are usually high. In this paper the chemical water treatments commonly used in the Netherlands will be described and some case studies of failure mechanisms in the water steam cycle will be discussed. Boiler and Burner Modifications to a Cogen HRSG Unit: Roger Allan, Corporate Engineer, Boiler Performance: Innogy Plc, Swindon, UK There have been a large number of tube failures in the main evaporator in the heat recovery steam generator at Innogy's 135 MWe cogeneration plant sited at Esso Fawley within the first 18 months of operation. An investigation indicated that the original natural circulation design suffered from dry out resulting in steam side corrosion. The design has been successfully converted to forced circulation with two pumps within the constraints of the evaporator envelope. The heat recovery steam generator can be operated in gas turbine exhaust mode as well as in forced draught

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mode with all the boiler heat supplied by its duct burners. It was observed that, in forced draught mode, the flames from the outlet duct burners were impinging on the furnace walls and causing considerable damage. A solution of changing the inlet aerofoils was checked using CFD modelling and has now been implemented reducing the temperature mal distribution to an acceptable level. Fin Design, Fabrication and Heat Transfer Enhancement in HRSG Boilers: P.Boone, Rosink GmbH, Germany A novel method of fabricating fins for HRSG tubes is described based on the "U" fin principle. This new technique offers greater fin density and heat transfer rates combined with acceptable pressure drops. A stronger bond between the fin and the tube is created preventing fin unwinding Operating Experience in High Supplementary Fired HRSGs for Co-Generation Plant: G Viswanathan, T Balakrishnan, S Sundaresan, BHEL, India In CCGT plant used for power generation, the HRSG design philosophy is to maximise heat recovery and steam generation. However even in base load plant there have been problems with the integration of the HRSG with the gas turbine, For example one problem is the wide variation in exhaust velocity at the entrance to the HRSG. In addition Captive / Cogeneration plants expect the HRSGs to meet requirements like increased steam output through high supplementary firing, maintaining rated steam temperature over a wide operating range despite changes in electrical output. New Italian Legislation for Pressure Equipment Design and HRSG Experience A Tonti, C Dell Site, ISPESL, Italy Since 1989 ISPESL has emanated dispositions for pressure equipment designed in the creep range according to time dependent mechanical properties. During the past years, on the base of the results of in-field examinations, the original procedure has been improved and sharpened through a series of new provisions. During the last two years ISPESL has proceeded to revise and update the emanated regulations. The procedure is now widely applied in Italian HRSG plants. Practical Approach to HRSG Life Management: A Jones, Powergen, UK During the mid to late 1990's a vast range of HRSGs were built across the UK, Europe and North America. These HRSGs were designed to operate under different design conditions, constructed to various design codes and often operated in ways that are not always consistent with the original design intent. Nevertheless, a number of similarities are inherent in the HRSG designs. During the presentation the following topics will be discussed. These include HRSG designs, failure locations and mechanisms, non-pressure part issues, creep life assessment, valve casting and header inspections, high temperature pipe work and flexible operation Providing a structured approach to creep life management of header, manifolds and pipework, in line with the GOM101 procedures, allows a selected programme of work to be completed at statutory outages. CCGT Modelling as tool for condition monitoring T al-Shemmeri, Staffordshire University; S. Pace, Connah's Quay CCGT Plant, UK This paper shows how thermodynamic modelling, using temperature pressures, fuel and air flows can in principle be used to identify incipient failures in both gas and steam turbine components as well as HRSG plant.

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