K
HI all,
We have 2 GE Frame 9E gas turbines at our facility. The design base load is 115 MW & ambient temperature of 28 degree Celsius and a Mark 5 control system. We have a 17 stage axial compressor, 14 canister type combustion chamber & a 3 stage turbine. Design turbine inlet temperature is 1124 degree Celsius. The first 2 stages of turbine buckets has internal air passages for cooling while the third stage does not.
Recently, in one of the gas turbines, both the third stage wheel space temperatures i.e. forward outer & aft outer have been registering differential temperatures of more than 30 degree Celsius 402\434 degrees & 284\310 degrees respectively. The wheelspace differential alarm is already persisting in Mark 5 MMI as one of the second stage forward wheelspace thermocouples in unavailable.
Is this wheelspace temperature differential likely to cause any problem? If so, at what temperature range should we think of a shut down? The manual mentions only absolute wheelspace temperature values as indicative of problems, which are well within limits. Also, no rising trend has been observed for the absolute wheelspace temperature values.
Also, some time ago we had an issue with 3rd stage wheelspace temperature rising for the same gas turbine. On shutting down the unit & on inspection, cracks had been observed in the exhaust diffuser struts. The same had been welded & the unit has been running fine. The newly procured exhaust diffuser from GE has already arrived at site & we are planning to replace the same also soon. My concern is whether these wheelspace differential values are also tell-tale of any problems in the exhaust casing. The wheelspace thermocouples' installation happened way back in 2011 but this phenomenon is a much more recent one [I don't remember when exactly it started].
We have 2 GE Frame 9E gas turbines at our facility. The design base load is 115 MW & ambient temperature of 28 degree Celsius and a Mark 5 control system. We have a 17 stage axial compressor, 14 canister type combustion chamber & a 3 stage turbine. Design turbine inlet temperature is 1124 degree Celsius. The first 2 stages of turbine buckets has internal air passages for cooling while the third stage does not.
Recently, in one of the gas turbines, both the third stage wheel space temperatures i.e. forward outer & aft outer have been registering differential temperatures of more than 30 degree Celsius 402\434 degrees & 284\310 degrees respectively. The wheelspace differential alarm is already persisting in Mark 5 MMI as one of the second stage forward wheelspace thermocouples in unavailable.
Is this wheelspace temperature differential likely to cause any problem? If so, at what temperature range should we think of a shut down? The manual mentions only absolute wheelspace temperature values as indicative of problems, which are well within limits. Also, no rising trend has been observed for the absolute wheelspace temperature values.
Also, some time ago we had an issue with 3rd stage wheelspace temperature rising for the same gas turbine. On shutting down the unit & on inspection, cracks had been observed in the exhaust diffuser struts. The same had been welded & the unit has been running fine. The newly procured exhaust diffuser from GE has already arrived at site & we are planning to replace the same also soon. My concern is whether these wheelspace differential values are also tell-tale of any problems in the exhaust casing. The wheelspace thermocouples' installation happened way back in 2011 but this phenomenon is a much more recent one [I don't remember when exactly it started].