I am hoping that someone can provide me with some information regarding crank cooling. My plant consists of 4 GE 7FA.04 GT's, and 2 LCI's. There are some senior employees who believe that crank cooling is not a good practice, but if it is necessary you should crank for 15 minutes, and then coast down for 15 minutes before cranking again. You would do this until wheelspace temps are below 150F.

In the research I've done it seems most facilities have their own procedures for accomplishing cooling via cranking, and there is not a set standard. Has anyone ever come across a GE technical standard regarding crank cooling? Even if you've never seen GE documentation, I'd still appreciate your input.

If you guys need anymore info about our plants set-up I'd be happy to elaborate.

 

I got a GE specification/docuemntation saying that the unit should be on cooling mode for 24 hours (minimun after shutdown)

Also GE recommand the unit turning /crank cooling continue for 48 hours to ensure uniform rotor cooling .

Will have a closer look on that subject on teh documentation that i got..and come back here ...

By the way where the plant is located ?

 

GER-3620n has this bit in it:
Prior to an inspection, a common practice is to force cool the unit to speed the cool-down process and shorten outage time. Force cooling involves turning the unit at crank speed for an extended period of time to continue flowing ambient air through the machine. This is permitted, although a natural cool-down cycle on turning gear or ratchet is preferred for normal shutdowns when no outage is pending. Forced cooling should be limited since it imposes additional thermal stresses on the unit that may result in a reduction of parts life. Opening the compartment doors during any cool-down operation is prohibited unless an emergency situation requires immediate compartment inspection. Cool-down times should not be accelerated by opening the compartment doors or lagging panels, since uneven cooling of the outer casings may result in excessive case distortion and heavy blade rubs. Cool-down is considered complete when all wheelspace temperatures are below 150°F when measured at turning gear/ratchet speed.

We let our 7FA's sit on turning gear for four hours after shutdown then crank cool continuously until the wheelspace temps are below 150F. I'll look back and try to see where we came up with the procedure.

 

A couple considerations we follow when doing so on site:

-This is considered an abnormal operating mode, only done if time constraints dictate
-Do not attempt when ambient temps are below -15*C
-Leave machine on ratchet for 2hr minimum before starting cranking motor
-IGVs to remain at min (34*)- this should be the case unless water wash has been selected on the HMI
-Do not open any compartment doors during forced cooling
-Cranking is stopped and cool down considered complete when all 6 wheelspace thermocouples read less than 65*C

Cheers