Dear all,

Can any one advise me how to run the turning gear when related controller unit need to be shutdown for maintenance/troubleshooting, because if we follow the procedure and wait for cooling of machine it takes 3-4 days and then we stop turning gear and perform activity and again need to run the turning gear for 6-hours and then startup...too much loss of production.

while during turning gear
auxiliary pump ON
Turning/Lifting pump ON
Turning solenoid valve energized
engaging solenoid valve energized

Please share your experience how to minimize down time

Cheers
Ashique Ali

 

You should be able to run the pumps in HAND or MANUAL.

You will need to find a suitable source of voltage/current for the two solenoids outside of the control panel. You would do well to make a small "panel" consisting of a couple of fuses (POSITIVE leg or HOT leg for each solenoid, at a minimum) and possibly some suitably sized switches (one per solenoid). Connect the power source to the "input" side of the switch/fuse assemblies, and temporarily disconnect the wiring from the output terminals of the control system and connect it to the "output" side of the fuse/switch assemblies.

Since this would be handy in the future, if you make it portable and kept in reserve, you could use it in the future if ever needed.

 

Dear CSA

thanks for your advise..basically i want power off the PCU when machine is on turning gear and turning should be ON for 3 hours then i power up the PCU and turning gear should be now back to normal. one thing i want to add that power supply to solenoid valves will be available but only the process control unit (PCU)of DCS system that gives contact to energize/de-energize them will be down. if we manually ON the auxiliary pump and turning gear lifting pump then how to keep the two solenoids energize where one is for engaging and other for turning.

Manually run the turning gear with this machine is very hard. this machine has manual mechanical pump that is only beneficial for emergency engaging/turning from HMI but continuous turning of this machine manually for 2 or 3 hours is hard and risk of ceasing is also available.

 

In other words, you need to find a way to energize the solenoids when the control system is shut down. And to be able to run the pumps, also.

And, it's suggested that you make this method a kind of permanent emergency fallback method by putting together something that can be quickly and relatively easily connected and disconnected.

 

well the turning/jarring gear runs the shaft at 3-8 rpm. you have mentioned that you need to run the following things

auxiliary pump ON
Turning/Lifting pump ON
Turning solenoid valve energized
engaging solenoid valve energized

for the auxiliary lube oil pump and Turning/lifting pump

find the MCC (motor control center) form which the power is given to the motors. Most of the control system i have seen does not allow manual start / stop of the motors without any controller interlock. check the electrical wiring diagram , you will find a similar looking circuit as i am uploading here.

http://www.2shared.com/photo/TtjLY2yS/sample_mcc.html

you need to bypass the PLC interlock so as to start from the local panel/module. find the interlock terminal and short it. now turn on the two motors. you will be able to stop the motors in a similar manner. usually only one interlock is given both for starting and stopping. find out how it is given and bypass the controller interlock for both. and yes don't forget to take it off once the job is done.

as for the energization of the solenoids CSA has given a good description of how it is to be done.

good luck and write to us how you fared in using the turning system without the controller.

note* - in your turbine, there will be a manual turning device. in case of a small turbine a small s rod type device given which can be directly connected to the shaft of the machine through a rotary gear and clutch. in case of larger machines, you will have a turning motor and there will be a mechanism for attaching the rod to the rotor of the turning motor. thus in case of any motor failure you can rotate the turning motor's rotor in hand thus in turn turning the turbine shaft.

 

Your original description read (and I'm quoting):

while during turning gear
auxiliary pump ON
Turning/Lifting pump ON
Turning solenoid valve energized
engaging solenoid valve energized

From that description it can be determined that the operation of the turning gear requires the energization of *BOTH* the Turning solenoid valve and the engaging solenoid valve.

Now you seem to be saying that there is some kind cycling or periodic energization of one or both solenoids during turning gear operation. If you only need to energize the engaging solenoid momentarily to start the turning gear operation, it would seem that two people with radios ("walkie-talkies") could perform that easily enough. A switch (momentary, spring-loaded push-button) could be used for the engaging solenoid circuit.

If it's more involved that that, then you might need to use a small PLC to accomplish this, if possible. I have seen some steam turbines that actually "speed up" (increase speed slightly) when vacuum is maintained or being brought up on the condenser, and in those cases the turning gear becomes disengaged, the shaft begins to slow and the control system has to re-engage the turning gear mechanism. But, that system requires speed pick-ups to sense speed and limit switches and is very complicated. A PLC could be designed to accomplish this, but it wouldn't be a simple or inexpensive.

So, I'm afraid you are on your own. If the information you originally provided is not the entire sequence that needs to occur then we can't be of much help. Have you tried contacting the turbine manufacturer/supplier for help?

When one is talking about "bypassing" some kind of control system, there is inherent risk involved with that. Either the risk is understood and mitigated to the extent possible, or the operation is deemed too risky and abandoned.

Best of luck in your endeavour.