European meeting validates topics under consideration for upcoming HRSG Forum

The fifth annual meeting of the European HRSG Forum (EHF2018), held May 15-18, in Bilbao, Spain, attracted 72 participants from 16 countries. Dr Barry Dooley of Structural Integrity Associates Inc, who chaired the meeting as he had done previously, considered the event “highly successful.”

EHF is supported by the International Assn for the Properties of Water and Steam (IAPWS), and is conducted in association with the Australasian HRSG Forum (AHUG) and the US-based HRSG Forum with Bob Anderson .

The recent European meeting featured 28 presentations, a panel discussion on attemperation, and a workshop on HRSG materials aspects. The highly interactive forum incorporated new information and technologies related to HRSGs, case studies of plant issues and solutions, and open discussions among users (18 owner/operators were represented in Bilbao), equipment suppliers, and industry consultants.

Dooley and Bob Anderson of Florida-based Competitive Power Resources, members of CCJ’s Editorial Advisory Board, both participated in EHF2018 and compiled the following meeting highlights:

    • International updates were provided on HRSG cycle chemistry, instrumentation, and FAC—including a review of recent IAPWS Technical Guidance Documents (TGD) in these areas. One TGD receiving considerable attention was “Application of Film Forming Substances (FFS). . . .”

    • Download this and other TGDs at no cost from the IAPWS website. 

    • Another high-interest area with no geographical boundaries: HRSG thermal transients associated with attemperators and superheater/reheater drain management.

    • A presentation on the impact of gas-turbine hot-gas-path and controls modifications on HRSG performance stressed the need to evaluate these impacts before executing the modifications. Of particular interest was the ability to use the Variable Load Path mod on Frame 9FA engines to eliminate long-standing problems with attemperator performance during startup. Anderson and at least some members of the steering committee for the HRSG Forum believe the VLP mod could benefit some US plants and are weighing its inclusion in next year’s program.

    • Two presentations focused on the value of using historical HRSG operating data to identify areas requiring attention to assure future reliability.

    • How renewable generation in combination with large-scale energy storage may impact gas-fired generation. Of particular interest were the details of high-capacity battery evolution and future possibilities. This is another subject under consideration for the HRSG Forum’s 2019 program.

    • A highly informative technical panel on attemperators with discussion among floor leader Anderson, Emerson/Fisher Valve’s Justin Goodwin, IMI-CCI’s Juan-Luis Dias, and Uniper Technologies’ Dan Blood. Dooley said the subject matter was on-point and discussion was driven by attendee interest areas and questions. Expect this and/or a panel on bypass systems at the 2019 HRSG Forum.

    • The group’s first specialist workshop on HRSG materials focused on the following:

1. The history of development of Grades 23 and 91 and their evolution—including the pros and cons of how ASME has regulated these materials and what can be expected of their performance going forward.

2. Oxide growth and exfoliation associated with ferritic materials in superheaters and reheaters. This information was particularly helpful in determining the degree of overheating in legacy HRSGs and for predicting oxide formation and exfoliation in HRSGs being designed with austenitic materials for higher steam temperatures.

   Informal discussions among attendees indicated some of the leading thinkers on exfoliation of steam-side oxide believe the ASME Code permits the use of T91 and P91 above what might be the safe long-term oxidation temperature. The simple translation is that owner/operators should expect an increase in solid particle erosion and superheater and reheater tube failures in legacy units. Attend the 2019 HRSG Forum to learn more about this critical subject.

3. Metallurgical examination as the first stage in a root cause analysis of HRSG tube failures.

    • The importance of cycle chemistry in combined-cycle plants was covered several presentations, including these:

    1. The latest guidance from IAPWS.

    2. The use of so-called Repeat Cycle Chemistry Situations for identifying future damage/failure.

    3. Examples of good plant-chemistry control practices.

    4. The importance of managing, vetting, and validating cycle-chemistry alarms to assure that the most important alarms are not missed. Anderson considers this an important topic with practical information not generally thought about by O&M personnel. It’s penciled in on the preliminary program for the 2019 HRSG Forum.

    5. The application of film forming substances for combined-cycle plants and how to identify hydrophobicity.

      • Repowering with gas-turbines was discussed by two presenters. One offered experience with dry cooling systems.

      • Case studies reviewed performance of dry-ice blasting and pressure-wave technology in removing external tube deposits.

      • Latest experience with gas tightness and movement of penetration seals.

      • Anderson presented case studies on how to identify and remedy the root cause of premature erosion in HP turbine-bypass pressure control valves. Severe erosion is caused by opening the bypass valve premature during startup. Such erosion also may be caused by wet steam ingested by the valve when depressurizing the HP system via the bypasses during pressurized layup. Discussed too were damaging thermal transients in high-energy steam piping when operating the bypasses during pressurized layup.

      • Extensive discussion and information on the optimal approach for HP-drum-to-downcomer cracking.

      • New technologies, including the latest HRSG designs for the Chinese market and the use of UV for treating boiler makeup.

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