Dear All,

We recently overhauled one of our 25MW GE Frame 5 MS5001PA Gas turbines with Sentinel C control system. It's been a little over six months since the unit has been running. For the past one month, we have been experiencing a high bearing drain temperature on Bearing No2 with LTB2D reading getting as high as 108-110 degrees Celcius at <16MW.

The following are the oil parameters;
Lube oil header pressure: 1.75bar
Main Lube oil pump discharge pressure: 2.6bar
Main Lube oil header temperature: 63 degrees Celcius at an ambient of >30degrees with 3 lube oil cooler fans running

We have pressure washed the off base lube oil coolers, to improve the cooling but no positive effect. when compared to the other units of same capacity but with MK V control system, the temperature a relative okay, with the highest value of 98 degrees Celcius.

Please what could be the cause of the high bearing no2 drain temperature?

 

First you have to compare the inplace monitoring with an independent even if temporary measurement.

 

Dear All,

We recently overhauled one of our 25MW GE Frame 5 MS5001PA Gas turbines with Sentinel C control system. It's been a little over six months since the unit has been running. For the past one month, we have been experiencing a high bearing drain temperature on Bearing No2 with LTB2D reading getting as high as 108-110 degrees Celcius at <16MW.

The following are the oil parameters;
Lube oil header pressure: 1.75bar
Main Lube oil pump discharge pressure: 2.6bar
Main Lube oil header temperature: 63 degrees Celcius at an ambient of >30degrees with 3 lube oil cooler fans running

We have pressure washed the off base lube oil coolers, to improve the cooling but no positive effect. when compared to the other units of same capacity but with MK V control system, the temperature a relative okay, with the highest value of 98 degrees Celcius.

Please what could be the cause of the high bearing no2 drain temperature?

 

Firstly,I assume the other bearings are experiencing normal temperature rise so your cooler is fine. Did anyone work on the bearing or instrumentation coinciding with the time you saw the temperature rise.I had a case once where a tech replaced a defective t/c with the wring type... ( type K with type T) I assume you are using thermocouples for your temperature measurement, so you need to compare the bearing temperature of all bearings with the machine at shutdown and cool down after a prolonged shutdown...this will eliminate the possibility of cold junction compensation errors. with the machine started up and online, trend the affected temperatures against the other bearings and header...do they all start from ambient temperature and see the affected one trend high? Did you do an oil analysis for babbitt material in the oil? Is the load gearbox oil tank vent pipe pulling a slight vaccuum with exhaust airflow when machine is online , if not this will cause the bearing to flood and cause this problem... If temperatures continue to rise, you can trim the oil supply orifice to get a little more oil flow and lower temperature....ensure your bearing temperature alarms and trip and functional.