if Gas turbine on standby more than 24 hours, then switch off the Turning Gear and Axu. lube oil pump. What will happen for DC lube oil pump?

note:
the Gas turbine we have is frame 7 E.
please any body can help me regarding to this matter.

 

Ayed,

Your posts are very difficult to understand.

We don't know what kind of "turning gear" your turbine has for cooldown operation. Many people refer to cooldown operation as "turning gear" even though the shaft is being ratcheted periodically, or on older machines the shaft speed was maintained at approximately 30-50 RPM using Aux. L.O. Pump discharge pressure ported through the torque converter. So, we don't know what kind of cooldown mechanism is in use at your site.

Next, when you say the turning gear and Aux. L.O. Pump are "switch off" do you mean that the operator has physically selected COOLDOWN OFF from the operator interface? Or do you mean that someone has manually shut down the turning gear motor (presuming the unit has a turning gear) and then manually shut down the Aux. L.O. Pump motor?

I would have to guess (without being able to see the sequencing or application code in the turbine control system at your site) that if the operator ended cooldown operation from the operator interface that the control system would wait for the shaft to reach zero speed after shutting down the "turning gear" and then shortly afterward would shut down the Aux. L.O. Pump. That would be a typical sequence, and the D.C. (Emer.) L.O. Pump would not start at all.

But, if the "turning gear" and Aux. L.O. Pump were manually shut down (or forced off from the operator interface) then I would suspect the D.C. L.O. Pump would come on for some time, and possibly even continue to operate, cycling periodically, until the cooldown operation was terminated by the operator.

Again, the post is not clear.

 

What CSA has said is correct. We have a 3 minutes on and 16 minutes off DC LOP cycle if the lube oil pressure goes low ( 63ql pressure switch) if the cooldown timer T62CD is not completed. This is to cool the bearings, assuming the required cooldown period is not over. But if this happens immediately after a trip / shutdown, then the DC lube oil pump will run for 30 minutes continuously and then the said 3 min-16 min ON-OFF cycle (here it takes the failed feedback of the aux LOP 88QA also).

 

thanks for your reply and interest.

i meant the turning gear and L.O Aux were forced shut down from CRT BRK after 24 hours.

actually we want to know how our system works in such a case.
note that our turning gear is operated by motor connected to a pulley then a gear box.

 

If you shut down your ALOP manually, what happen to seal oil? Seal oil will come on by itself on LOW seal differential pressure. I think we should start seal oil first if we manually going to shut down the LO system. Please correct me if I am wrong.

Thanks

 

Sardar9,

Late in the 1980s, GE and their packagers developed and started supplying air-cooled generators for use with Frame 7E/EA and Frame 9E heavy-duty gas turbines instead of hydrogen-cooled generators. The air-cooled generators are physically larger than their hydrogen-cooled counterparts, but, they have the advantage of not requiring hydrogen for cooling, nor CO2 for purging, nor hydrogen purity monitoring equipment, nor Seal Oil for maintaining hydrogen pressure/integrity inside the generator casing.

The issue here seems to be: Why was the turning gear motor and Aux. L.O. Pump motor shut down by opening their motor starter circuit breakers instead of an operator selecting COOLDOWN OFF from the operator interface to terminate the cooldown operation normally?

The answer to the original question (regardless of how/why the motors were shut down) has been provided. Even if the unit has a hydrogen-cooled generator, the D.C. Emer. L.O. Pump would react as previously described. If there was a Seal Oil Pump, it would be started in an attempt to try to maintain Seal Oil pressure.