Borescope Reduces Time for Gas Turbine Inspections
By Douglas J. Smith, IEng
SIEMENS WESTINGHOUSE has developed a patented high temperature borescope for the inspection of hot parts in gas turbines. The high temperature borescope can visually inspect, measure and photograph a turbine’s hot path at temperatures up to 1,000 F, thus allowing inspection to begin as soon as four hours after turbine shutdown. Older borescopes cannot be used until the turbine has cooled to 150 F. As a result it can take up to 24 hours after shutdown before inspections can start.
Borescope reduces time for gas turbine inspections. Photograph courtesy of Siemens Westinghouse Power Corporation.
The lightweight borescope was designed and developed to reduce outage time and enhance unit availability. A thin-wall aluminum tube allows cool air to be pumped through the tube to a camera positioned at the end of the probe. The telescoping tube can be extended from 41-126 inches. If an inspection finds damage the camera takes digital photographs for immediate analysis and evaluation by the engineers. Access for the borescope to the hot sections is gained through removable pilot nozzles. With the borescope, inspection of different parts of a gas turbine’s hot sections can be performed in as little as 15 minutes. According to Siemens Westinghouse the borescope and its camera can be used worldwide and adapted for a wide variety of gas turbines.
Lakeland Electric Completes Inspection in Two Days
At Lakeland Electric’s McIntosh power plant in Florida, Siemens Westinghouse used the high temperature borescope for scheduled maintenance inspection of the transition between the combustor and the first stage blading of the gas turbine. Inspection of the transition was completed in two days. The unit was removed from service on a Friday and was back online on Sunday.
After a four-hour cool-down period, and a safety check of the unit, the pilot nozzles were removed and the probe inserted. The inspection team performed the inspection at a turbine temperature estimated at 1,000 F. If discrepancies were identified, photographs would have been taken and transmitted to engineering within ten minutes.
According to Tim Bachand, Engineering Manger, Energy Supply, Lakeland Electric, using the hot borescope for inspecting the transition saved the plant approximately twelve hours of outage time. By reducing the outage time, the plant is able to save a minimum of $4,500 an hour from lost generating revenue. On a particularly hot day the savings could triple, says Bachand.