We have a frame 6B gas GE gas turbine. recently we have noticed a repeated starting failures due to starting device trip. The starting diesel engine speed is normal 2175rpm but the turbine has tripped at various speeds (35% to 47% tnh).

Sometimes the start attempt has succeeded but the others not. Does this means that the diesel engine is not the cause of trip as it sometimes complete normal sequence and the turbine synchronize? during troubleshooting the problem view2 and viewq functions have been used and they revealed that the jaw clutch limit switch change its signal before the starting device trip.

Does the clutch opens due to loss of torque from diesel engine or from a wrong signal from limit switch?

For a test can we make a logic forcing for the limit switch during start to eliminate the possibility of wrong feedback or its dangerous as there is a possibility of the opening of jaw clutch actually and as the trip signal is forced the jaw clutch would be broken.

Thanks for your quick feedback

 

Pretty well sure it is the clutch limit switch setting. The vibration of starting makes the switch open and trips the diesel engine.
It's so easy to reset the switch setting I wouldn't be bothered thinking about logic forcing

 

It means you need to troubleshoot the alarm by looking at the sequencing or application code that generates the alarm to see what can cause it.

We could make some generalizations, but only the sequencing or application code running in the Speedtronic controlling and protecting the unit and auxiliaries at your site have the specific answers to your questions.

We have no idea how old the unit is at your site. How long has it been since the diesel had any periodic maintenance, like changing fuel filters? Or air filters? Or any maintenance on the diesel fuel control mechanism (most older ones were hydraulically-operated by a hydraulic system on the diesel, controlled by solenoid outputs from the Speedtronic)?

How old is the torque converter? Has it ever been refurbished?

Is the unit accelerating slower on the failed attempts?

Do you have any means to trend shaft speed and diesel speed and compare it to previous good starts?

What other alarms (Process and Diagnostic) are annunciated during the start attempt or when the trip event occurs?

We would need to see a chronological printout of all the alarms for a period of, say, two minutes prior to the trip, and for 30 seconds after the trip, to be able to say exactly what tripped the turbine.

 

We have a similar problem like yours in our site. it was the torque converter on the unit. we change which finally solve the problem.

 

The problem has finished as the jaw clutch has been replaced due to excessive wear on the clutch hub and shaft splines.

Thanks alot to all who have gave advices.

regards

 

Thank you for the follow-up!