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Hlynur Steinarsson
22-09-2002, 09:37 AM
The right type of compressor is also importent!
I have worked on reciprocating comp. which where on a two stage system with NH3. The compressors where not ment to run at low kapacity and when they did the discharge temp. was around 130-150°C. The result was poor oil return to the compressors because of a poor seporation. Way to much oil went to the system and made some problem there. Nothing could be done exept we change to a better oil which and got a little bit better oilreturn.
So pic the right compressor if you are running on low kapacity f.e. coldroom during the night and using NH3. Otherwise you will have problem with discharge temp.

SteveDixey
29-09-2002, 04:25 PM
We get the same running some Sabroe 16 cylinder reciprocating compressors at reduced capacity on a freezing plant.

The easy answer, if your control system allows it, is to get the control system to load up the compressors for a couple of minutes every ten minutes of part load running to push some gas through and then offload back to part load.

If the compressors run part load for too long we get 150 deg. C head temperatures on a few cylinders which is enough to cause seizing. A change to PetroCanade Reflo 68A oil has also helped to reduce problems here as high temperatures used to thicken up the normal mineral oils after only a few hundred hours of use, meaning high oil carry over and reduced ability to get into the critical areas.

These two changes have meant no problems at all for the last 6 years, where before we almost totally wrecked one compressor and had serious damage on two other incidents before we guessed what might be happening.