AHOP Problem


Thread Starter


We have Frame V gas turbine and we are facing problem that AHOP doesn't developing pressure beyond 50 Kg/Cm2 and our normal requirement is 90-100 Kg/Cm.

We have carried out the following activities:

1) AHOP Pump overhauling done and installed.

2) Hydraulic oil circuit flushing carried out.

3) Hydraulic manifold components like PRV & Check valve dismantled and cleaned and installed back.

4) Hydraulic manifold cleaning also done.

After above activities still we getting only 50 Kg/cm2.

Pls suggest any idea to solve this problem.
We can start gas turbine with 50 Kg/CM2 hydraulic oil pressure?

Matter most urgent.
You have a Frame <b>5</b> gas turbine (only Speedtronic control systems use Roman numerals for identification; turbines do not).

I presume when you are referring to AHOP that you mean an AC motor-driven Hydraulic Oil Pump--not the Main, Accessory Gear-driven Hydraulic Oil Pump.

One of the many problems is that people believe that the <b>RELIEF</b> valve in the hydraulic system is the <b>PRESSURE REGULATING</b> valve. And it's not. The relieve valve on the manifold with the air bleed/check valve is there to provide a "safety" back-up to the built-in compensator on the hydraulic pump in the event the built-in compensator fails.

One must make sure the relief valve pressure setting is above the desired system pressure. The only way to do this is to adjust the pump's built-in compensator to a pressure higher than the relieve valve setting, then adjust the relieve valve to correspond to the value in the Device Summary, then reduce the built-in pump compensator setting until the relief valve stops relieving and set the compensator to maintain the desired hydraulic system pressure, as defined in the Device Summary (for the pump compensator setting).

Also, if the unit has a hydraulic accumulator, are you sure the accumulator is properly charged and the valves on the accumulator are in their proper positions? Usually, if there is a hydraulic accumulator it serves the Main and Auxiliary Hydraulic pumps, but there can be different configurations with multiple accumulators.

If the unit has a Main Hydraulic Pump (Accessory Gear-driven), then you can probably start and run the unit without the Auxiliary Hydraulic Oil Pump. Even at CRANKing speed speed, the pressure developed by the Main Hyd. Oil Pump should be sufficient to start the unit. The Auxiliary is primarily there in case something happens to the Main when the unit is on-line and running. Many turbines don't have an Auxiliary Hydraulic Oil Pump, only a Main (Accessory Gear-driven) pump and start and run just fine.

Lastly, have you inspected all the tubing and piping for the Aux. Hyd. Oil Pump? Including any tubing to the Accessory Gauge Cabinet, and all valving on the Accessory Gauge Cabinet? Many times the compression fitting have come loose and leak oil, and because most of the tubing and fitting are in the L.O. tank, they are difficult to observe.

Please write back and let us know what you find.
We have also checked all tubing and found ok. Then also our problem not rectified.

Finally we have replaced Auxiliary hydraulic oil pump with new available spare with same motor. Then we got sufficient pressure.
I think the gap between AHOP pump gear increases is the main problem.