after the GE MarkvI had been on turning gear for 5 days it was shut down for a maintenance job on the oil gauge. After the job, it was to be put back on turning gear. The cooldown mode was selected.

After the speed got to 20rpm, it came down to zero with "Starting means cooldown trouble fault" alarm. On observation, the turning gear coupling had sheared. What can be responsible for this damage?

 

>after the GE MarkvI had been on turning gear for 5 days

First of all, the Mark VI is the turbine control system for a gas turbine--not the gas turbine.

Second, we don't know how the turbine has been operated or for how long it's been in service.

Third, it's highly unlikely that the problem was caused by the Mark VI--unless there were other alarms (Process and Diagnostic) that operators and their supervisors ignored prior to initiating cooldown operation.

Fourth, it was written that an oil gauge was to be repaired. In what part of the "oil system" was the gauge located.?.?.? Is it possible that some manual isolation valve or flange blind was installed that wasn't removed prior to initiating cooldown?

 

what are vibrartion reading? was there any alarm for vibration either H or V or thtust bearing? or , lub or control oil pressure alarms?

this can not be happened without any of alarms I mentioned?

 

ahdash,

The turning gear coupling of the Mark VI was broken.

There usually aren't any vibration sensors or bearing metal temperature sensors on the Mark VI turning gear coupling.

And have you ever seen a "starting means cooldown trouble fault" alarm? I've seen "starting means fault" alarms, and "cooldown trouble" alarms, but never a "starting means cooldown trouble fault" alarm.

I continue to learn new things about the Mark VI every day. I wonder how fast the Mark VI spins on turning gear. And I wonder how all the wires connected to the Mark VI keep from getting all twisted and tangled when the Mark VI is on turning gear. Maybe the wires just got too twisted and the turning gear torque broke the coupling of the Mark VI turning gear. I should have thought of that before.

Oh, and I wonder where they found a new oil gauge for the Mark VI?

Perhaps I'll learn something new about the Mark VI tomorrow. Maybe more than one thing.

 

The Ge design does not have any vibration sensors that are consistent with turning gear speed-be it 6 or 30 rpm(which ever you have) It wouldn't mean anything anyway, as the speed is too low to bother. If the machine was started on TG after an outage(as you imply)and then sheared the TG gears/pin/coupling, I would suspect your lift oil hoses are ruptured. These machines are not very robust, and a little rotor drag due to lift oil not high enough will wreak havoc on the drive gears/clutches.

I don't know offhand the MK XI data points for the lift oil, but you should be able to see the them in the historical data-if the oil pressure was low, there should have been alarms generated to warn the operators prior to TG operation.

The MK XI also has bearing prox probes that can tell you if the lift is shifted one way or the other(from the two lift ports on the bearings)

 

sggoat,

The original poster hasn't said what Frame size machine was involved. I've personally never seen an F-class turbine which ran above 6 or 7 RPM on turning gear--and he said it went to 20 RPM and then coasted back down.

I also don't think the original poster is going to write back, so I think this post should be considered null and void.

And, anyway, it was the Mark VI turning gear coupling that sheared.