Session chair and discussion leader for the LM2500 breakout sessions is John Baker, O&M manager for Calpine Corp’s Bethpage Energy Center, Hicksville, NY. Focus of the day’s presentations was the depot findings, which included the following:
Compressor front frame
(1) Stationary air seal issue. Old material is a composite and not repairable when cracked or damaged. New product is aluminum, providing increased resistance to cracking.
(2) Oil droplets and accumulation noticed by operators. Oil was not leaking from a seal; rather it was coming from the area between the sump cavity and No. 4 supply strut. A frame replacement is required; there is no authorized repair. The leak is not preventable.
HP compressor rotor
(1) Wear of a spline adapter was traced to deposits of red sludge found blocking the component’s oil galleries. Preventive measures include regular monitoring of oil pressure and A-sump scavenge oil temperature, plus visual checks of filter. Note that use of HTS oil is not recommended by the OEM.
(2) Airfoil erosion on the leading edge of IGVs and Stage 1 blades; mechanical erosion ultimately led to crack with major consequences downstream. Some affected turbines inspected by depots were operating in dusty or sandy environments, which may (or may not) be significant. Look for rough airfoil surfaces and inspect frequently if identified. Replace worn or suspect parts.
(3) Stage 1 one-off blade event. Engine in close proximity to a marine environment experienced a steady increase in vibration, which eventually triggered an alarm and manual shutdown. Blade separation caused heavy downstream compressor damage and light damage to “hot-section” modules. Power turbine not affected. Inspection revealed airfoil erosion and pitting in early stages. FOD not suspected. More frequent inspection for airfoil pitting and corrosion recommended.
(4) Stage 7 blade event on unit also located in a marine environment. Only 2000 operating hours; damage thought initiated from the suction side. Full-stage borescope inspection recommended together with regular maintenance of air inlet filters.
(5) Fogging ineffectiveness an issue with a majority of users. Heat rate actually can go up in some cases. One user got a 2-MW enhancement but he was in the minority.
(6) Offline water wash. Some users recommend monthly frequency but that depends on the unit’s duty cycle. No hours-based standard has been established. There was general agreement that heating wash water increases cleaning effectiveness.
- Insurance. Several users expressed dissatisfaction with insurance companies that want shorter inspection intervals than the standard, forcing adjustment of maintenance schedules.