OIL SEPARATOR not working properly

Hello,

I have a problem in one installation, I'll like to see if you might help me find the solution. Refrigerant NH3

We have install 2 recip compressors 6 cilinders each. Working by polley, 1060 RPM Each has it's own standard oil separator 20'' diameter.

Working conditions are:
Suction Pressure: 18 - 20 psi
Discharge Pressure: 170 psi
Differential pressure oil: 45 psi
Oil Temperature: 122 F
Oil used: Texaco capella WF 68
Suction Diameter Pipe: 6''
Discharge Diameter Pipe: 2 1/2''

Each equipment are working 24 hrs a day, and are carrying oil a little bit more than 1/2 Gal/Day

The compressor manufacturer inform me that's the correct carry over, but the oils separator is not working properly.

We check and there's no obstruction on the oil return system. We open the float valve and looks, like no oil has pass for it.

Do you have any idea of what's going on??:confused::confused:

Quote:

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Originally Posted by PEPELEBU

Hello,

I have a problem in one installation, I'll like to see if you might help me find the solution. Refrigerant NH3

We have install 2 recip compressors 6 cilinders each. Working by polley, 1060 RPM Each has it's own standard oil separator 20'' diameter.

Working conditions are:
Suction Pressure: 18 - 20 psi
Discharge Pressure: 170 psi
Differential pressure oil: 45 psi
Oil Temperature: 122 F
Oil used: Texaco capella WF 68
Suction Diameter Pipe: 6''
Discharge Diameter Pipe: 2 1/2''

Each equipment are working 24 hrs a day, and are carrying oil a little bit more than 1/2 Gal/Day

The compressor manufacturer inform me that's the correct carry over, but the oils separator is not working properly.

We check and there's no obstruction on the oil return system. We open the float valve and looks, like no oil has pass for it.

Do you have any idea of what's going on??:confused::confused:

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PEPELEU.
Welcome.
Thanks for all the info so far.
Personally I would like to ask what make are the comps and what age are they.
Because 1/2 a Gallon a day of oil being carried over sounds excessive to me.
Normally I would say with that amount of carry over, your comps. need servicing! (depends on the answers to the questions asked in this post)
Also your oil diff. pressure could well be a little high, but that would depend on the make and model of the Compressor.
Another Highly relevant question.
Is to what level are you filling the sump. Basically what is the oil level when running.
If you could post these details I suspect we may be able to help!
Cheers Grizzly

PEPELEBU
You could also check oil return float mechanism.Does it open + shut Sometimes if float seat leaks , high pressure hot gas blows oil out of crankcase giving symptoms you explained.

Grizzly, and RANGER1

Thanks on your comments, we already check the oil return float mechanism and it looks that its working ok. but you don't see like ever any oil pass trough it.

Grizlly, the compresors have 980 hrs, so they are brand new.

Also good question on the oil sump, on the eye sight glass is half. Some times you could see like the oil has some foam. I think this is because it migh be entering some wet gas on the suction side. Do you think this could be the problem?

We check with factory of the compressors and they inform us that for this open compressor 1/2 of Gal, of oil carrying is the usual. (Over this conditions), the problem is that the oils separator is not working at all...... by theory, should hold 50% of the oil carry over so we'll have in our system 1/4 gal per day at the most.

Returning oil can be tricky at times.
I guess the oil you are looking for is in the evaporator.
-Is the evaporator higher than the condensing unit?
-Is the returning oil pipe from the saperator goes to the compressor or the suction line before the liquid saperator?

I dont think that there is something wrong with the oil saperator, try to increase the suction pressure and therefor increase the refrigerant flow to return oil.

Suction line diameter looks too large to me, have it rechecked.

Never heard of 2 1/2 diameter copper pipe. are you sure?

it looks to me that your problem is in the design and not instalation.

Chemi:)

Quote:

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Originally Posted by chemi-cool

Never heard of 2 1/2 diameter copper pipe. are you sure?

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I do not belive he meant copper-since this is a ammonia system:eek:

Quote:

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Originally Posted by PEPELEBU

We open the float valve and looks, like no oil has pass for it.

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Quote:

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Originally Posted by RANGER1

Does it open + shut Sometimes if float seat leaks , high pressure hot gas blows oil out of crankcase giving symptoms you explained.

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If the oil float appears "dry" with no oil, then check the oil drain line from the float valve. If the line is hot then hot gas is flowing through the valve and down into the crankcase of the compressor. This can increase the oil carryover just as RANGER1 explained.

1/2 gallon of oil leaving the compressor every day is excessive and not correct. I doubt the compressor should loose this much oil in a month!

Hi,
had this kind corrections, leak valve, oleata flows on crank and spraies down on cilinder, centrifuge isn't base on much oil. Foam in compressor, warm back pipe - repair replacement valve.

PEPELEBU,
If you are concerned about liquid refrigerant possibly entering sump (as you see foaming ) check underneath cylinder banks between sump cover and head and look for ice formation/sweating that looks unusual. It should be warm to hot to touch.Also measure discharge temp,pressures at same time.
With an oil temp 122 deg f its unlikely.
An 18-20 psi suction on nh3 would be pushing a reciprocating compressors design limits, so tempreture of discharge would be interesting.Most machines would have a maximum of 140 deg c (284 deg f ) to 150deg c(300 deg f) depending on brand and especially if its unloaded .
Is the oil return line cool or hot ?
Does it have liquid injection in suction line ?
Is it water cooled or thermopump cooling ?

After reading again, would also suggest with 1000hr operation oil seperator will still be filling up ,unless you primed it to correct level ?.The seperator is quite large and depending where float level is in relation seperator take off point it may take awile to return oil.If you would like to see a quicker result prime up oil seperator.

Quote:

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Originally Posted by RANGER1

After reading again, would also suggest with 1000hr operation oil seperator will still be filling up ,unless you primed it to correct level ?.The seperator is quite large and depending where float level is in relation seperator take off point it may take awile to return oil.If you would like to see a quicker result prime up oil seperator.

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That's a good point, but after 1000 hours of running time and pumping 1/2 gallon of oil per day I might say the oil separator would be filled up by now.

If the compressor is pumping this much oil and has been doing so for some time there is a lot of oil out in the system. Is this begin drained off in equal quantities as the oil being put into the compressors?

Quote:

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Originally Posted by RANGER1

P
An 18-20 psi suction on nh3 would be pushing a reciprocating compressors design limits

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20PSi Suction is not even close to pushing the limits of a recip on NH3, as long as there is sufficent Horsepower.
We need to know what kind of Compressors and Oil Seperator you have.
(Sorry for the mispellings and such, just had eye surgery and the screen is a blur)

NH3LVR ,
You are right temp would be about 116 deg C.But if its a sabroe if it gets bellow 50 load % it would be close to 150 deg C.After i posted it i thought about it , but then to late

Guys,

thanks for all your comments.
Let me clear to Chemi, this is an NH3 system so NO copper pipes.
RANGER 1, I think that maybe because we have a larger oil separator, and it's so new, It might be filling up.
I'm going to do some new measuring on the oil carry over levels, and also check some of you'r comments.
I hope that for the end of the week I have some new information.

Hello Pepelebu,

I know it's a simple idea but since it is a new system, are all the filters clean ? In return line system oil filters etc.
Maybe during building some dust, dirt etc. jamms up the filters.
Are there also filters in the separator? maybe they are dirty or broken for any reason bcause then the separation also doesn't work.