Hello every body

i'm very happy to join your awesome community which in-riches my little acknowledge about gas turbines.

i'm working on GE MS9001E and the torque converter is transmitting motion to the crank motor and turning gear during normal operation despite it shouldn't do.
Is anybody having an idea about this?

 

sherif elzoghby,

When did this problem start? After a Maintenance Outage? Or was it just recently noticed/reported to operations/maintenance?

It IS very normal for the output shaft of a Voith torque converter to rotate when the turbine is running and the starting/cranking motor is not running. It is NOT, however, normal for the input shaft (which is coupled to the starting/cranking motor) to also be turning.

There should be at least one (1) solenoid-operated valve on the output of the torque converter, 20TU-1, and some older units also have a second solenoid-operated valve, 20TU-2. I would suggest you check to ensure that both solenoids (if two are present on your machine) are de-energized, and more importantly, that neither solenoid-operated valve is sticking in the energized condition when the unit is running and the starting/cranking motor is not running.

The torque converter is really a hydraulic pump (driven by the starting/cranking motor) and a hydraulic motor (which turns/accelerates the turbine-generator shaft). It's very difficult to imagine how the hydraulic motor (driven by the turbine-generator shaft) could become a pump and push hydraulic fluid "backwards" towards the hydraulic pump and, hence, converting the pump into a motor turning the starting/cranking motor shaft under normal circumstances. When either or both of the torque converter solenoid-operated valves are de-energized there should be no oil (except that used for lubrication) between the hydraulic components of the torque converter.

So, it would seem that something is not allowing the oil between the hydraulic components to drain to the L.O. Tank. I believe some units have a manual isolation valve on the discharge of the torque converter, and if this valve were not in the fully open position then the condition you are reporting might occur.

Lastly, review the Starting Means P&ID to ensure all components (electrically-operated and manually-operated) are working correctly. Again, it's not enough for a solenoid-operated valve to ensure that it is de-energized when it should be de-energized as the internal components can bind or stick causing them not to return to the de-energized state.

Please write back to let us know what you find. "Feedback is the most important contribution!"(c) here at control.com and it's what makes this forum so different and useful. If someone, anyone, can take a few minutes to ask a question or for some information, they can spend a couple of minutes to let others know if the information was useful or not and how they managed to resolve their problem.

 

Dear CSA

Sometimes using in some gas turbine an orifice in drain and remove 20TU.
Effect the efficiency of the torque converter?
Can it create problems?

Thank you

 

mohamad noruzi,

No. The use of orifices and/or solenoids have all been considered in the longevity of the equipment during the design of the systems.

Torque converters, are by their nature, devices with "slip", and they do wear out. It all really depends on the usage they receive. I've been to sites that have all manner of "problems" establishing flame and accelerating to FSNL that contribute to higher than "normal" usage of the starting means, both the starting/cranking motor and the torque converter. Other sites seem to crank excessively, either for off-line water washes or for accelerated cooling to be able to take the unit off COOLDOWN earlier than would normally be possible for whatever purpose (sometimes it's completely unwarranted; it's just that "they've always done it that way" without understanding why or what the adverse affects were). In these cases, the torque converters seem to fail at a faster rate than other sites which don't have a lot of "continuous" start attempts and/or don't perform an excessive amount of accelerated ("forced") cooling.

Dirty oil is also not good for many of the torque converters used on smaller Frame units (such as Frame 5s and Frame 6Bs, usually made by TwinDisc). As with bearings and hydraulic systems, oil quality and condition can adversely affect torque converter operation and longevity.

But, the design of the systems was done with the longevity of the equipment in mind. Remember: GE heavy duty gas turbines are designed and controlled and protected with one thing in mind: Reliability. And that means that all systems have to be designed with optimal parts life to make them as reliable as possible.

 

thank you very much for your help CSA and Mohamed.

about your inquiries CSA this problem was noticed since the commissioning procedure, specially the crank motor meggering when it was decoupled with the main shaft.

there isn't any isolation valves at discharge lines and there is one solenoid 20TU-1 which controls the hydraulic solenoid 33TC-1.