We have manual ratcheting jacking system. For this we have to remove the accessory coupling. Other than removing the coupling, is there any other way to rotate the turbine rotor?
I have seen people remove the load coupling, wrap a LONG nylon strap around the load coupling (overlapping the wraps), attach a chainfall to the free end of the strap and the hook of the chainfall to a piece of structural steel nearby, and use the chainfall to slowly rotate the shaft. It is necessary to re-wrap the strap depending on its length, AND it's necessary to make sure personnel are clear in case the strap slips off the coupling so they don't get hurt.
If you're just borescoping, you should be able to have the Aux. L.O. Pump running, and if there is a bearing lift oil pump/system ("jacking oil") you should also have it running when rotating the shaft.
Hope this helps!
(This isn't really a controls-related issue.... Though if the unit has a ratchet "jog" push-button that could probably be used--just don't know enough about what GE Belfort is/isn't putting on their units these days, and of course, the OP didn't tell us if the unit has one or not. We seem to be getting a LOT of these lately.... This one is relatively simple, but isn't related to controls really at all.)
What a difference a word makes.!.!.!
"I have seen people remove the load coupling COVER, ....
Remove the load coupling cover, at the generator rotor end of the coupling, then wrap a long, wide nylon strap around the coupling and use a chainfall to pull on the end of the strap to slowly rotate the turbine-generator shaft.
I'm proven to be a poor proofreader of my own writing. Apologies for any confusion.