Oil pressure problem

[Anil.y]

Hello every body...

I had change the compressor oil in a compressor. After that it started to trips in oil pressure. In the part of oil changing i change the liquid line filter also. Charged the oil up to 50% of crank case.
Any body can please help me in this problem..?
Compressor Details:

Name: Copland
Type: Reciprocating
Stage: 2-stage
Refrigerant: R404a

[frank]

Is 50% of crank case measured in the sump sight glass?

Did you leave the compressor with the crankcase heater on for 6 hours before you started up?

What level of oil can you see in the sump sight glass when if fails on oil pressure?

[install monkey]

worn oil pump, dirty oil sump filter- faulty oil press diff switch?

[monkey spanners]

Its the oil the right grade? If its too thin it may cause tripping.
Have you checked the oil switch to see if it is working ok?

[passandscore]

What are your operating pressures? (Discharge, Suction & Oil)

What make & model of oil pressure switch do you have? Do you know how to check it for proper operation?

[Anil.y]

55% of oil when charged.
Leave the compressor heater switch on up to 8 hrs before start it.
Regular using oil with suitable grade.
No problem with the Pressure switch.
"HP 12 bar, OP 1.5 bar, MP 1 bar, LP -0.6 bar and Oil level is 10%" these are the readings before the compressor going to trip.
Oil coming from the separator very minor quantity.

[monkey spanners]

Did you put the same amount of oil back in that you took out?

[install monkey]

oil pressure switch diff setting weak, wind it down a turn so it trips below 1.3 bar oil press- as long as the oil isnt foaming

[PaulZ]

Hi Anil
Why did you change the oil in the first place?
I would only change the oil in a R404 system if there was an problem with filters / strainers blocking, dirty oil, acid in the oil or other contaminates.
Paul

[passandscore]

I agree with install monkey. Differential is a little weak.

Perhaps this literature will help. You forgot to mention the make and model of your oil failure control.

Copeland Sentronic:

1) http://www.emersonclimate.com/europe/ProductDocuments/CopelandLiterature/EN_TI_D070801_OilPressureSafety_0.pdf

2)http://www.hvacrinfo.com/cope_ae_bulletins/TAE1275.PDF


Johnson Control:

http://cgproducts.johnsoncontrols.com/MET_PDF/121400.PDF

[cadwaladr]

Sounds like the wrong oil to me or bad quality,why was it not tripping prior to oil change or was it?.

[Anil.y]

I done this as per my customer request.
Yes I add the same amount of oil(10trs) back to the compressor.
If it is a problem with pressure switch and its setting, Why it didn't happen before!!?
The customer using that same quality oil from the beginning of the plant.

I tried a lot upon this. I feel some thing else that which i can't guess behind this. May be it is simple or hard thing!!! Still i'm chasing this problem.

[monkey spanners]

Something else to think about, if the system trips on another control which then resets such as low pressure etc, depending on how the control circuit is wired the oil switch will trip once the compressor has been of for approximately 2 minutes.

[PaulZ]

Hi Anil
To get an answer to this problem we need some more information on the system.
When you changed the oil did you do anything else?
What is this compressor operating on, storage freezer, blast freezer or is something much colder?
You say you have a LP of -0.6 bar this is a suction temperature of -64 oC, is this correct for the system?
The difference between LP and MP is ok, if this is air cooled then the discharge pressure of 12 bar is a bit low.
The more information you provide the better.
Paul

[Anil.y]

Hi Anil
To get an answer to this problem we need some more information on the system.
When you changed the oil did you do anything else?
What is this compressor operating on, storage freezer, blast freezer or is something much colder?
You say you have a LP of -0.6 bar this is a suction temperature of -64 oC, is this correct for the system?
The difference between LP and MP is ok, if this is air cooled then the discharge pressure of 12 bar is a bit low.
The more information you provide the better.
Paul



You are absolutely right.
the working temperatures between -65 oC to -70 oC
Compressor working on a vapor absorbing condenser.
The performance of the compressor is good but after running 4 to 5 hours it's starting triping.
At that time OP gradually decreasing and becoming equals to MP.
working with TEV, water cooled condenser, Gas level seems to be OK(17kg).
I changed the liquid line filter which is looks like chocked.

[GHAZ]

hi put some pantene in it, it will stop the oil from thickning at those low temperatures and will give you a good oil return and delivery through oil pump