we have 3 gas turbine of GE frame 6 at our site. in one of the gas turbine it fails to breakaway. checks done:

1.ratchet motor able to do ratchet.
2.diesel engine rotating at full speed.

i have doubt on torque converter as a gauge mounted over does not shows any pressure when the machine fail to breakaway. the torque converter is of voith company and has quite a reputation.

kindly guide me through this.

 

This could be a problem with the torque converter itself or a problem with the foot valve in the lube oil tank which feeds oil to the converter. The fact that you have zero pressure on the discharge kind of points to the foot valve.

Do you have any Voith representative near you who could help you to check?

 

rvs_gasturbine,

Recently I have been to two sites with diesel starters where the units either didn't break away from zero speed or had problems during acceleration resulting in very high exhaust temperatures (because the control system was putting in a LOT of fuel trying to help with acceleration resulting in hitting the exhaust temperature limit and the unit stalling for several minutes).

BOTH sites had no records for any refurbishment or maintenance activities of the diesel starter. BOTH sites INSISTED the diesel was running at rated speed, but couldn't prove that with any actionable data (oddly enough, but units did NOT have speed pick-ups on the diesel engine which were connected to the Speedtronic turbine control system).

How do you know the diesel is rotating at rated speed?

One of the sites was found to have a failed foot valve in the suction of the torque converter oil feed line (the foot valve is in the L.O. reservoir). The failed foot valve was blocking oil from getting to the torque converter, and the resulting heat build-up in the torque converter during start attempts meant a person couldn't put their hand on the torque converter casing. The foot valve was temporarily repaired and the unit was able to break away and accelerate nearly normally.

Subsequent to that, the site replaced one of the diesel hydraulic linkage solenoids (the one setting the full speed of the diesel) and then it was unable to break the unit away from zero speed again. It was discovered that the linkage wasn't adjusted correctly after the solenoid was replaced and once adjusted the unit could accelerate normally from zero speed to rated speed.

The other site continues to blame the Mark V for all issues with starting the gas turbine, and has done nothing to check the diesel speed (though they insist it's running at rated speed), and has done nothing to inspect or verify torque converter operation.

Neither of these units have torque converter solenoids, used to control either the rate of filling or draining of the torque converter. Does the unit at your site have a solenoid associated with the torque converter? (Refer to the Starting Means P&ID.) If so, has it been checked?

Some torque converters also have strainers in the suction of the torque converter, with no differential pressure gauge, switch or transmitter. If the torque converter has such a strainer, has it been checked/cleaned recently?

Diesel engines do get tired and need refurbishment from time to time. They also have air filters which, amazingly enough, get quite forgotten in normal gas turbine maintenance activities.

And, torque converters also get worn and need refurbishment. Your reference to reputation is not clear (is it a good reputation, or a poor reputation; is it just the torque converter on this particular gas turbine, or all of these manufacturer's torque converters in particular).

 

rvs_gasturbine,

In case of GTG Lube oil Tank level below the requirement also, Torque convertor fails to function for breakaway initiation during acceleration which is practically experienced and witnessed by me at one of the works, later set-right.