Compressor seal oil setting

[zayed eid]

I have some thing I would like some one to explain to me. we have a centrifugal compressor with suction pressure 150 PSI and the discharge is 560 PSI. The setting for the seal oil PDCV is 35 PSI above the suction pressure. Why the setting for the PDCV is connected with the suction pressure ? the discharge pressure is higher then the suction pressure. Why it is not connected to the discharge pressure?!

 

[JJPellin]

One of the seals is directly adjacent to the suction eye of the first stage impeller. It is impossible for this seal to experience pressure any higher than suction pressure. The seal on the opposite end is on the other side of the balance piston. There is a balance line from this end that runs directly back to the compressor suction. This seal could only see a pressure significantly higher than suction pressure if the balance piston fails or the balance line becomes blocked. If this occurs, the thrust bearing will fail, so the pressure to the seal is really not your biggest problem.

Review the cross-sectional drawing of your compressor and this should be evident. The reference to the seal oil differential pressure controller should connect to the balance chamber. This may be slightly higher than suction pressure.


Johnny Pellin

 

[georgeverghese]

The seal oil feed pressure, in addition to being somewhat higher than max normal suction pressure, it must also be somewhat higher than the max normal shutdown - settleout pressure of the blocked in compression train.