Good Evening,

We are facing an issue with Hydraulic pressure low problem in Hydraulic system which is used for GT Servo valves operation. When we operated the AC hydraulic pump the pressure is not developing more than 10Bar. We have inspected the Hydraulic module and suction line, tried to regulating valve and inspected check valve, but no luck. Then tried to adjust pump pressure relief valve, no changes in the pressure.

Prior to issue, the team removed the lube oil from tank to attend the internal inspection, then fill it back to tank and oil purification carried out. After completing the oil purification, AC lube oil pump started and kept in-service for an hour and venting done accordingly. Then team started the Aux Hydraulic pump and hydraulic filters vent ports kept open for few minutes to release the traps, during this operation Observed that there was no pressure developing in the system.

Hence, The pressure not changing even adjust the pressure compensator, I am suspecting Pump having an issue to develop pressure.

Pls review the above case advise on root cause analysis.

 

jagadeesh_73680,

Use the P&IDs to go through the Hydraulic System systematically. That's always the thing to do in cases like this. At the hydraulic "block" where the relief valves and air-bleed check valves are located if the relief valves are relieving there is usually a very large flow of oil--with only one Aux. Hyd. Pump running the flow is usually enough to cause the current drawn by the AC motor to exceed the TOL (Thermal OverLoad) relay setting and annunciate a Process Alarm. AND, that flow should be visible to the naked eye. There should NEVER be flow coming out of of the pressure relief valve(s)--they are there to protect the pumps. The pump pressure is to be set using the pressure compensator on the pump. (I presume GE Belfort, or BHEL, is using the same pumps GE has used without trouble for decades--OH, sorry, that would be too smart of GE Belfort to do; they ALWAYS have a better idea and change things simply for the sake of change because they know better than GE USA (even though they haven't been building GE-design heavy duty gas turbines as long as GE USA...!).)

But, I digress. Check all of the hydraulic filters, the transfer fill valves, and the drain valves, to be sure they aren't open. ALSO, check all of the gauge and pressure switch bleed (drain) valves to be sure none of them were left open (they should have been opened for flushing).

If the Aux. Hyd. Pumps are also used for bearing lift oil pressure, be sure the pressure regulator valves are properly set and the solenoids are working properly (again--refer to the system P&IDs). If there are flushing blocks where the servo-valves usually are then flow will be very high (again, check the current drawn by the AC motors!) and that will usually prevent reaching normal hydraulic system pressure (with the flushing blocks installed--and flushing blocks should have been used if the intent was to clean all piping and devices which use L.O., which usually includes the Hydraulic system.)

That's about all I can offer at this point. USE THE P&IDs--always. Systematically. Always.

Please write back to let us know what you find!!!