We have TurboCare gas turbine. Since 1 month ago it is failing to start due to an unknown reason.
The starting system is diesel engine connecting with turqe converter type (VOITH Torque Converter EL9 YGTM 4.0-86).
The tubine starts to purge then ignition but when the speed become 1500RPM it is stopped by thermo regulation (temperature increase inside turbine).
We checked pilot and main fuel gas but all were ok.
I think the problem in the turqe converter but (turqe converter not accelerating the turbine to self sustained speed. Maybe variable guide vane not opening. Actualy I dont know if this guide vane will change opening during startup or not, and if yes, how this control will work.
Please help me to solve this problem.
1st you need to check torque converter drain valve for proper operation, i.e. draining/not draining lube oil. if it is working properly then the problem is mostly with your starter (lazy starter).
I have never heard of a TurboCare turbine, but I know of a turbine services company named TurboCare. Can you tell me if the turbine in question was actually manufacturer by TurboCare, or possibly refurbished and/or relocated by TurboCare?
Can you provide any other information about the turbine? How old is it? How many megawatts does it produce? How many combustors does it have? What kind of turbine control system does it have?
Thank you in advance!
Dear CSA & nldgseeker,
Thank you very much for your reply.
Mr. CSA, here is the Data you requested:
1- Turbine is manufactured by FIAT Company
2- commissioning date 1910
3- it has 17 combustors
4- control system is Siemens step 7-400
I checked the torque converter and I fined that variable vans is modified to be in fixed state. so the acceleration will be only by the diesel engine. diesel engine has a speed up to 1800rpm AND CONNECTED to the torque through a gear box.
Again thank you for you help, and I am waiting your advice
Hmmm. Methinks there is something amiss with the data you provided (the commissioning date.?.?.?)
You said the starting means was a diesel engine, and you said that thermal protection was the cause for the aborted start (trip?).
Diesel engines do require maintenance, and the fuel rack can drift over time (it's presumed the fuel is controlled by a mechanical mechanism, sometimes called a "rack"). These are two possibilities; I have seen diesel engines which had had NO maintenance other than oil changes over 20 years that were just worn out and tired (the rings and valves, specifically). During that time as the diesel wore, the I&C technicians kept increasing the fuel control to put more fuel into the turbine to help it accelerate due to the loss of the torque from the diesel engine starting means. This causes the exhaust temperature to increase, and at some point it usually hits the maximum allowable limit which either clamps (limits) the fuel flow to prevent damage from overtemperature (overfiring) or causes a trip due to excessive temperature.
The other possibility is that the torque converter is also worn and needs refurbishment. They, also, experience wear over time--and, again, the I&C technicians are not above continually increasing the fuel flow-rate to compensate for the loss of torque being transmitted to the point the internal temperature hits the maximum allowable limit or trips on overtemperature. The torque converter is simply a hydraulic pump driving a hydraulic motor. And, the high pressures the torque converter operate at can and do cause wear of the internal components of the torque converter.
Some control systems will automatically try to compensate for the drop in torque and increase the fuel without any intervention by the technicians. But, the ultimate effect can be the same.
Hope this helps! While the turbine control system can be manipulated over time to overcome the loss of torque (either due to a worn engine or a worn torque converter) there will come a time when it finally hits a limit, and while it appears it's the control system it's really not.