PSM: Rotor repair and lifetime extension solutions

More power? Better heat rate? Faster ramp rate? FSNL in less than 10 mins? Lower load points? More Fuel Flexibility? Longer maintenance intervals? PSM will be presenting a live webinar at the 7FUG 2020 Digital Conference on June 30, entitled “What else do you need from your 7F power plants?” All GT owner/operators are able to join as many solutions are applicable across fleets.

PSM’s presentation, “F6B rotor repair and lifetime extension solutions for improved lifecycle costs,” on the final morning of the Frame 6 Users Group’s 2019 conference, offered an alternative to the OEM’s LTE program described on the previous day.

The presentation began with the requisite “who we are and what we can do for you,” shop locations, international affiliations, numbers of LTE projects completed and the frames involved, availability of seed rotors for swaps to eliminate outage time, rotor-disk manufacturing experience, computer program and analysis capabilities for modeling, materials analysis, NDT capabilities (eddy current, ultrasonic, microstructural review, etc). You can access information of interest on the Frame 6 website. 

What might have been the most interesting segment of this presentation for hands-on users came at the end—recent findings.

Example 1: 7EA compressor-rotor distress was identified in multiple locations—specifically pitting in disc webs and distress in blade slots previously blended and/or cracked. FCD was said to accelerate aft slot cracking; previously blended slots re-cracked during the subsequent interval.

Example 2: Rabbet-fit cracking was attributed to improper interference between disc snaps. The speaker said PSM reviewed critical specifications and ran calculations before shop personnel were allowed to “chase out” the crack. Re-contouring of the OEM’s geometry was said to produce a life benefit.

Example 3: A 6B rotor (more than 5000 factored starts and about 40,000 factored hours) was found to have a flaw in the first turbine wheel, which was attributed to fast starting of the machine. Calculations and modeling conducted based on site data predicted the failure and suggested a material change and design refinements that would improve low-cycle fatigue life.

Example 4: Inspection of a 9E compressor revealed blade-slot cracks that had migrated through the rim. Multiple indications also were found on pumping vanes. Plus, cracking was found in the counterbore of the forward turbine stub shaft. This led engineers to believe in the possibility of component retirement during the upcoming LTE; they suggested the owner/operator develop a contingency plan.

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