Dear All,

We are encountering a problem that I didn't face before with Frame 9E, a power plant reported that Frame 9E unit couldn't achieve Turning Gear Operation
History of Events :
the unit was running on full load and the customer shut down the unit, the unit didn't go to Turning Gear operation the machine goes to 99 RPM speed and the turning gear motor started but it fail to increase the speed to 120 RPM and goes to zero speed in about 2 mins time.
The operation Team Tried again to start the crank motor and put the unit on turning gear in a time of 20 mins but without success.
The operation team found the Rubber coupling of the Turning gear motor damaged and they changed it.
the operation team left the unit for two days until the wheelspace temperature is below 67 Celsius and tried to put the unit again on turning gear but without success ( doors were closed but I'm not 100 % sure that the ventilation fans were stopped and the Lube oil pump was left running )
Hence. it was observed in the last attempt that Bearing Number 3 Temperature is a higher by the other bearings by 20 Celsius ( Temperature sensors on that bearing will be checked )

the Team checked several issues that can be the source of the problem.
1- checked the Lift oil pressure they confirm that the pressure is good 240 Bar, the flow control valves on the generator bearing were cleaned also
2- Torque converter Drain valve 20 TU was checked ( Reference and Feedback ) and was found to be in good condition.
3- performed a megger test on the Turning Gear motor ( 3 phases ) and the Readings are 9.9 G.OHM and 10.1 G.OHM and 11.2 G.OHM respectively
4- dismantle the Acc. shaft cover and Rotate the Rotor using a hydraulic Jack and a Ram and they report that the rotor rotated easily without any rubbing sounds observed.

Today we tried to operate the unit again and put on Turning Gear after more than 10 days the unit is stopped and just the lube oil system was running.
the Turbine Goes into 99 RPM speed and the turning gear motor started but the speed didn't increase and kept going down until 20 RPM and then it goes up and reached 119 rpm, and now the Turning Gear speed is going up and down.
Hence. when the speed of the turning Gear goes down, the temperature of bearing Number 3 is increasing and reach to alarm values, and when the speed increase more than 80 rpm it start to stabilize. ( we will check the probes for sure )

Note : unit was reported to run on high vibration after major inspection Bearing number 3 ( seismic vibration was reading 11 mm/sec ) before unit shut down, the vibration was analyzed before and was confirmed it's because a resonance in Exhaust casing causing the vibration to increase in bearing number 3 area ( bearing 2 and 4 are totally normal readings )

Thank you for your cooperation in advance.

 

Hello

Can you tell us if Control command/system of that Starting/cranking motor have been checked properly and operates acccording to the installed application code/program/software on the Turbine controller/governor

What is installed control system??

With more datas we can be better help and support and this case..

Regards,
James

 

No reply so we can suppose that this thread is closed ...

Shame on you to come here and post a thread then left it without giving answers to menbers of this great Forum ...

 

Hi Ahmed,

This is similar issue with Frame 9E gas turbine which is using Mark VIE Control system. if you are facing turning gear issue can you perform below operation.
1. If turning gear not Connect there are Angle from Torque converter normally before turning its on Max position 68 degree. once RPM of machine coast down first it will initiated command to 88QB pumps to start and maintain Bearing lifting header pressure normally 230 Bar to 250Bar. if pressure is not sufficient at header or pressure switch is active with low then start another pump and keep both pump in operation and try to engage Turning gear.
2- If Turning gear failed with this method Try to bring machine on Crank mode and start Crank to bring machine on force cooling till you fix Lift oil system pressure.
3- Once Machine wheel space is at minimum stop machine and bring machine at Zero RPM this is safer to keep machine on standstill and take remedial action.
4- Check Torque converter angles and there limit switched for feedback on Turning Angle need to be 43 Degree on Frame 9E. If Limit switches are working properly then check Filters for 88QB and Torque converter which might get clogged and can not provide proper pressure.
5- Start both 88QB Pump and install a Lift gauge on Shaft and try to measure is there any lift while Pumps are Running if not then stop both Pumps There are flow control valve Normally Flow control valve has Indication for flow Reverse these Flow control valves position then start both Pump in this step you will have less pressure with Max flow due to diversion of Flow control valves.
Check again with Measurement gauge how much lift you have on Shaft.
6- If you received low pressure alarm for 88QB keep the low pressure switch signal force to keep running both pumps during start up or turning gear Operation. Recently we have faced similar issue with Shaft stucking and turning gear not engage. we have done mentioned operation and temporary we can run the machine without losing production for long time.
7- Regarding High Vibration and low RPM of Shaft during Turning gear as you know Lube oil has Viscosity if lube oil viscosity is High due to Low temperature inside tank Pump can not provide proper pressure at discharge as well for Connected system Till system reach Minimum temp of lube oil 40c RPM will gradually increase and once temp of lube oil is normal RPM does not has any impact. During only cooldown operation keep CCW pump off till increase oil temperature at acceptable range to avoid low rpm issue on shaft.
8- Check both temp sensor on Bearing-03 this could be one of sensor is faulty or if both sensor is reading same values then a corrective action can be taken for Lube oil cooling system and return and supply line can be check for any blocking.

If you need any more information please feel free.