O&M, Major Equipment: Tenaska Lindsay Hill Generating Station
Borescoping steam-turbine stop/control valves
Tenaska Lindsay Hill Generating Sttion
Tenaska Alabama Partners LP
845-MW, gas-fired, 3 × 1 combined cycle located in Billingsley, Ala
Plant manager: Robert Threlkeld
Key project participants: Mark McKenzie, operations manager; Vince Crabtree, maintenance manager; Claude Couvillion, O&M support manager
Challenge.
During cold starts and minimum load operation, the steam-turbine stop/control valves are required to operate at the lower end of their control band. When the valves are operated at less than 20% open, the velocity of the steam that passes through them is greatly increased and has the potential to cause erosion of the valve components. A regular inspection is the only method to determine if any erosion has occurred. Disassembly of the valves is costly and requires a lengthy plant outage.
Solution.
The plant installed inspection ports using the existing after-seat drain piping on the stop/control valves. A piping tee was installed in the existing 2-in. drain line for borescope inspection. The valve stem and body can now be inspected by removing the inspection cap from the tee. At the completion of the inspection the cap is welded back into place.
Results.
The borescope ports have reduced the cost to perform the inspection of the steam-turbine stop/control valves by about 90% and reduced the outage time by several days.
