Dear all.
In our frame 5 units ,when the unit reach FSNL and during the electrical AC pump goes out the trip( control ) oil pressure decrease and the unit trip.but when we put the AC pump in manual mode and start DC pump then release AC pump and then release DC pump the unit continue in operation and reach FSNL. PLEASE ANY ONE CAN KNOW WHATS THE PROBLEM.
REGARDS

 

@enigmad,

Use the L.O. System AND Control Oil System Piping Schematic drawings (P&IDs) to see what kind of problem with either relief valves or check valves might be causing your problems. Usually the Trip Oil system uses a gravity-operated swing check valve and they have been know to "stick" in the wrong position from time to time, especially on older machines with poorly maintained L.O. The drawing isn't going to tell you exactly what's wrong--but you should be able to follow the lines to see where check valves are located in the piping/tubing and then find the valves, remove them, and test them for proper operation.

The Trip Oil relief and check valves ARE NOT connected to or controlled by the turbine control system. Rather, they are gravity-operated or spring-operated and the control system relies on them to work properly because it has no way of knowing the physical condition or state of the valves.

Whenever you encounter a problem like this--almost ALWAYS a mechanical problem, NOT a control problem--use the Piping Schematic drawing(s) to find the devices on the drawing which might be causing the problem and then go out to the machine and find the devices and remove/test/clean them to verify proper operation, reinstall, and test for verification.

Finally, you mentioned VPR-1 and VPR-2. They ARE NOT connected to or controlled by the turbine control system; again, the turbine control system relies on them to work properly. The only way the control system "knows" if they are working properly is by the feedback from the pressure switches in the system(s)--which could also be a part of the problem. Either the manual block and bleed valves of the pressure switches are in the wrong positions, or the switches are failing intermittently. But, again, this would technically be a mechanical problem (probably under the purview of the Instrumentation Department)--but not technically a control system problem.

Please write back to let us know how you resolved the problem!

 

Dear all.
In our frame 5 units ,when the unit reach FSNL and during the electrical AC pump goes out the trip( control ) oil pressure decrease and the unit trip.but when we put the AC pump in manual mode and start DC pump then release AC pump and then release DC pump the unit continue in operation and reach FSNL. PLEASE ANY ONE CAN KNOW WHATS THE PROBLEM.
REGARDS

It seems the issue is only in AUTO operation. When the AC pump trips, control oil pressure drops and the unit trips, but in manual operation with AC and DC pumps the pressure is maintained and the unit runs up to FSNL. This points more to a problem in the AC pump auto control, a weak check valve, or a pressure switch/sensor issue rather than the pumps themselves.

 

@enigmad,

Use the L.O. System AND Control Oil System Piping Schematic drawings (P&IDs) to see what kind of problem with either relief valves or check valves might be causing your problems. Usually the Trip Oil system uses a gravity-operated swing check valve and they have been know to "stick" in the wrong position from time to time, especially on older machines with poorly maintained L.O. The drawing isn't going to tell you exactly what's wrong--but you should be able to follow the lines to see where check valves are located in the piping/tubing and then find the valves, remove them, and test them for proper operation.

The Trip Oil relief and check valves ARE NOT connected to or controlled by the turbine control system. Rather, they are gravity-operated or spring-operated and the control system relies on them to work properly because it has no way of knowing the physical condition or state of the valves.

Whenever you encounter a problem like this--almost ALWAYS a mechanical problem, NOT a control problem--use the Piping Schematic drawing(s) to find the devices on the drawing which might be causing the problem and then go out to the machine and find the devices and remove/test/clean them to verify proper operation, reinstall, and test for verification.

Finally, you mentioned VPR-1 and VPR-2. They ARE NOT connected to or controlled by the turbine control system; again, the turbine control system relies on them to work properly. The only way the control system "knows" if they are working properly is by the feedback from the pressure switches in the system(s)--which could also be a part of the problem. Either the manual block and bleed valves of the pressure switches are in the wrong positions, or the switches are failing intermittently. But, again, this would technically be a mechanical problem (probably under the purview of the Instrumentation Department)--but not technically a control system problem.

Please write back to let us know how you resolved the problem!

Dear

@enigmad,

Use the L.O. System AND Control Oil System Piping Schematic drawings (P&IDs) to see what kind of problem with either relief valves or check valves might be causing your problems. Usually the Trip Oil system uses a gravity-operated swing check valve and they have been know to "stick" in the wrong position from time to time, especially on older machines with poorly maintained L.O. The drawing isn't going to tell you exactly what's wrong--but you should be able to follow the lines to see where check valves are located in the piping/tubing and then find the valves, remove them, and test them for proper operation.

The Trip Oil relief and check valves ARE NOT connected to or controlled by the turbine control system. Rather, they are gravity-operated or spring-operated and the control system relies on them to work properly because it has no way of knowing the physical condition or state of the valves.

Whenever you encounter a problem like this--almost ALWAYS a mechanical problem, NOT a control problem--use the Piping Schematic drawing(s) to find the devices on the drawing which might be causing the problem and then go out to the machine and find the devices and remove/test/clean them to verify proper operation, reinstall, and test for verification.

Finally, you mentioned VPR-1 and VPR-2. They ARE NOT connected to or controlled by the turbine control system; again, the turbine control system relies on them to work properly. The only way the control system "knows" if they are working properly is by the feedback from the pressure switches in the system(s)--which could also be a part of the problem. Either the manual block and bleed valves of the pressure switches are in the wrong positions, or the switches are failing intermittently. But, again, this would technically be a mechanical problem (probably under the purview of the Instrumentation Department)--but not technically a control system problem.

Please write back to let us know how you resolved the problem!

Dear WTF?
We cheked the check valves it is gravity type and seems ok. Also pressure switched are in good condition and we saw the pressure decreasing in the gauges also , i mean the pressure droop was real .

 

It seems the issue is only in AUTO operation. When the AC pump trips, control oil pressure drops and the unit trips, but in manual operation with AC and DC pumps the pressure is maintained and the unit runs up to FSNL. This points more to a problem in the AC pump auto control, a weak check valve, or a pressure switch/sensor issue rather than the pumps themselves.

Dear Beab.

We cheched the ckeck valves and pressure droping was real and we saw it in the gauges . Do you think VPR1 cause this problem ?