Screw Compressor shared oil skids ? good / bad concept 1

[jamesbanda]

Dear all,

I am working on a project using screw compressors. I have been recommended for 2 or 3 compressors to use only one oil skid.

I think this is a really bad idea due to reliability - lose one skid and all compressors shutdown.. but i want to validate my perspective v industry best practice.

In my experience i've never seen this but what are others..
our unit size is too big to have one compressor..and we are reusing older ones as well in our configuration..

 

[JJPellin]

I work in a large oil refinery. We have some compressors that share a common oil system and have not been a problem. Our preference would be for individual systems. But, if that is impractical or too expensive, we would set requirements for the common system as follows: Two oil pumps with auto-start on the auxiliary pump. Two oil coolers with a good switch valve to switch on the run. Two oil filters with DP monitoring, vent connections, pressure equalization line between filter banks. Accumulators sized to smooth out any pressure transients when switching coolers or filters. DCS trending of oil pressure, pump run status and common trouble. The oil system needs to pass a stability test when it is built. We have a particular test that requires simulating all common single component failures. The unit has to pass the test with no trip conditions met for the compressors. You have to be able to switch filters or coolers, trip off pumps, falsely auto-start pumps, etc. and not reach any trip conditions for the compressors.

I assume you are referring to a common lube oil system rather than a flood oil system on flooded screw machines. We have some flooded screws with common flood oil and there are some other particular issues with those systems that I am probably not qualified to address.

Johnny Pellin

 

[zdas04]

What is on the oil skid? I would envision maybe an oil pump and a coalescing filter and possibly some storage? This looks like a false economy to me. If you just want to run one machine you'll have to run the oil pump which would be 3 times as large as required for the single machine.

The oil is hydrophillic and managing its temperature is critical to successful operations (oil contaminated with water has a different coalescing diameter, different lubricity, and different viscosity, you have to cook the water out of the oil for long-term, trouble-free operation). This seems to be more difficult with longer piping to the filter.

I wouldn't do it on a bet.

David

 

[sterl]

A single separator with a secondary low pressure return vessel or section is not so uncommon, and lends economy to certain other approaches including heat recovery from the oil and single point charge management, even a "slave" purifier arrangement when the compressed fluid is "dirty".

But using a single oil pump/single filtration/single pressure management arrangement for multiple machines is much riskier as both parties indicate.

What are you compressing and what does your duty cycle look like?

 

[zdas04]

My assumption was the oposite of Johnny's, please let us know if you are talking about lubrication oil or flood oil. It really matters.

David

 

[jamesbanda]

We are actually considering using a shared oil lubrication system on screw compressors.

(Personnaly i think it is a bad idea) but i professional need to evaluate it fairly. Therefore has anyone used a shared oil lubircation system on screw compressors to save money.