seal oil leakage on centrifugal compressor

[rotw]

We have a two 2 MW natural gas feed centrifugal compressor barrel type that is still equipped with a seal oil system. Upgrade to dry gas seal is foreseen but not immediately.
We are currently experiencing leakage and seal oil coming out of the vent both on the seal assembly as well as on the vent coming out of the seal oil tank.

It seems the seal oil tank pressure is increasing abnormally but not completely sure.
Any idea of what can be at the root of this? The seal oil system and lube oil system are separate.

Thanks in advance for any orientation.

 

[rotw]

I would like to add that the oil leakage on vent coming out from seal gas assembly happens only on one end of the machine which is on the discharge side.

 

[JJPellin]

I would suspect excessive separation gas to one or both seals. This is typically air but can be nitrogen. I would remove any purge gas from the reservoir. This is typically nitrogen and serves no purpose on most systems. There could be a restriction in the drain line. I would check to make sure the vent off the contaminated seal pots is open. This could go to flare. I would make sure that the buffer gas is not misadjusted. What is the seal configuration?

If there is a flame arrestor on the tank, have it cleaned and inspected.

Johnny Pellin

 

[georgeverghese]

It is common to see seal oil dissolving heavy components in natural gas at high pressure - this may be the cause of the high pressure in the seal oil tank. Lean oil absorption plants for natural gas C3 / C4 extraction run on the same principle.

 

[rotw]

JJPellin & georgeverghese
Thanks for the input, I will revert seal configuration asap.

 

[georgeverghese]

There have been many cases of fires in compression trains due to seal oil tanks with coninuous flammable gas release - all from seal oil based barrier fluid shaft sealing systems in hydrocarbon service compressors / expanders.

As suggested, the current tank vent should be routed to flare or to some safe location with a flame arrestor or similar.

 

[JJPellin]

We are still waiting for some more specific information about the configuration of your seals and the design of our seal oil system. With more details you are likely to get better advice.

Johnny Pellin