7F Users Group dives deeper into engine issues

The 7F Users Group steering committee has realigned the program for its annual meeting to focus exclusively on the world’s most popular frame gas turbine. For several years prior to the 2016 conference at Orlando’s Rosen Shingle Creek hotel, May 9-13, the agenda had expanded to include robust sessions on heat-recovery steam generators (HRSGs), steam turbines, and generators.

Coverage of other equipment associated with F-class combined-cycle plants has been moved to the Power Users Group’s summer program (this year August 22-25 at San Antonio’s La Cantera Resort; register now!), which features concurrent meetings of the Combined Cycle, Steam Turbine, and Generator Users Groups. Those three organizations, plus the 7F Users, are managed and conducted under the Power Users umbrella.

One casualty of the program change was the loss of the traditional Monday morning HRSG workshop conducted by HRST Inc. In its place this year was a seminar on the repair of F-class hot-section components conducted by TEServices Inc. HRSG topics, including presentations by HRST engineers Lester Stanley and Bryan Craig, are integrated into the August CCUG program. Important to note is that the Power Users website features an HRSG Forum among its online offerings; sign up today at no cost.

TEServices’ Hans van Esch and Shaheen Hayatghaibi divided their four-hour program into two parts: The first concentrated on inspection and repair of hot-section components; the second on rotor inspection, a hot topic today given the rapidly accumulating starts and operating hours of 7F engines.

Van Esch organized his presentation on component repairs into six parts—an arrangement that is easy to follow and has proved successful over the years as the foundation for the company’s semi-annual three-day training program on the metallurgical aspects of industrial gas-turbine component refurbishment.

He began by explaining to attendees how his six-steps philosophy is conducive to assuring quality repairs, reducing costs, and improving the safety of 7FA operations. Implementation of the recommended program, the speaker surmised, would facilitate communication with the OEM regarding price, delivery time, explanation of findings, etc. In addition, owner/operators will be better informed to qualify less-expensive alternative vendors, which also may offer benefits in delivery time and quality of repairs and coatings.

The speaker next offered an overview of the six steps to success regarding HGP parts inspection and repair; details are available here. Steps 1, 2, and 3 provide the methodology to do the following:

      • Review component degradation onsite.

      • Create a checklist for each HGP component in your engine.

      • Compile repair and coating criteria and specifications for each component.

      • Focus on degradation in the past and expected in the future.

      • Select and audit a repair facility for each group of components.

      • Make use of contacts at other end-user organizations and consultancies.

Steps 4 (A and B), 5, and 6 suggest follow-up to ensure your decisions are meeting expectations. Example: Verification of component degradation assists in making better decisions on optimal intervals between inspections, as well as better selection of repair and coating technologies and of vendors providing those services. Van Esch gave special attention to advanced assessments and life-extension programs for extending inspection intervals and/or longer parts life.

The presenters emphasized that verification of repairs (Steps 4-6) is required for the OEM as well as alternative services providers. They believe the OEM shops are no better than others, and even with an LTSA in place, the end user takes the lion’s share of the risk if a repair is not performed well.

Hayatghaibi and van Esch also discussed TEServices’ recommended approach to component life extension. Access the details (“Extending 7FA parts life beyond the OEM recommendation”) in the CTOTF Presentations Library by scrolling back to material from the fall 2013 meeting. In that presentation the two speakers said owner/operators have three options:

      • Accept OEM recommendations as gospel and follow its guidelines. This is the lowest-risk alternative and also the most costly.

      • Ignore all recommendations and proceed with business as usual. This is the lowest-cost alternative and also the most risky.

      • Decide on an acceptable level of risk, then define which damage mechanisms can cause failure and address only those issues in formulating a life-management program. This is TEServices’ recommended course of action.

Wrapping up, here’s what attendees seemed most interested in:

      • TEServices’ 7FA bid/repair specs and how to use these without removing the repair facility’s responsibility/warranty.

      • Evaluation of quality programs at OEM repair shops, as well as those in place at third-party shops.

      • How to extend inspection intervals and component lifetimes.

      • Limitations of braze repairs.

      • Bucket cutter-teeth configurations, benefitsof aluminum oxide coating, and pre-grooving of shroud honeycomb.

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