A Hot Gas Path Inspection (HGPI) of GE Co-Generation train revealed an extensive failure of the turbine blades and vanes in the first, second, third stages and combustion chamber cross firing tubes. Subsequent investigation effort indicated that commissioning activities of associated compressor water wash system allowed large volumes of water to penetrate the compressor and combustion chamber due to improper instrumentation interlock configuration of MOV-20TW-1 (Offline compressor water wash motor operated valve) and MOV-20TW-3 (Online compressor water wash motor operated valve). The field wiring for the valves was incorrectly interchanged causing the offline water wash valves to be operated while commanding the online water wash valves to operate and vice-versa. Compressor water wash system is typically used to remove fouling deposits from compressor components to maintain the equipment efficiency, power output and reduce corrosion rate. Vendor recommends daily online water wash while the offline water wash shall be performed whenever the equipment is not working. As a result, cross firing tubes were exposed to sudden quenching during the water wash activities causing tube fragmentation, which found its way through the exhaust stream to the turbine chamber — colliding with associated buckets and nozzles — eventually resulting in the reported damage. Water seeped into the air extraction line and settled in the dryer skid system, resulting in desiccant contamination. Following turbine shutdown for correcting the instrumentation loop configurations of subject MOVs, the contaminated desiccant flowed to the combustion chamber, blocking the extraction line and the drain lines. After successful configuration of compressor water wash system MOVs, the turbine was put back in operation mode. The contaminated desiccant blocked the air passage of the combustion chamber, which consequently melted the cross firing tubes and contributed to the overheating of first stage buckets. Investigation concluded that the inadequate pre-commissioning procedure — for the Co-Generation train compressor water wash interlock system — were the root cause behind the subject incident. The immediate cause was determined to be water penetration to the compressors and combustion chamber internals during machine operation.

This content is only available via PDF.
You do not currently have access to this content.