Operating Gas Turbines under Adverse Load Demands

From left to right: Typical blades damage (Foreign object damage) of gas turbine | Gas turbine blades, (100 MW ABB) Connaught Bridge Power Station

Gas turbine blades represent the highest cause of failures, and on this basis manufacturers (OEM) recommend very specific operational hours upon which an inspection (overhaul) is required. In reality Power Station Operators often cannot remove an apparently healthy machine for such inspections when there are high load demands imposed onto the Station (and nation’s electricity grid) especially when the Station also has other turbines down (non‐availability).

We were involved in assisting the Station in vibration severity assessment of a gas turbine which could not be removed for a scheduled inspection. We undertook gas turbine blades integrity assessment based on vibration measurements and analysis which were bench marked against statistical deviations of good conditions (blades passing frequencies and wavelet analysis). Risks of blade failures and financial risks of failures versus forced outage were evaluated‐ upon which the turbine was operated beyond OEM’s recommendations. The unit subsequently operated safely by an additional 16,000 hours before it could be brought into scheduled maintenance.

Our involvement and technical assistance to the Station was acknowledged in a published paper at the Power Plants’ Users Conference in Thailand.

“The combined savings to CBPS was about RM48 million”

Ir Ng Boon Hee
(Rtd) Station Manger, Connaught Bridge Power Station (CBPS), Tenaga Nasional

Wavelet analysis (in additional to Blades Passing Frequency sidebands) used in blades vibration severity and faults detection.