Oil Pot Plugged?

[NH3-Iceman]

Greeting I am New Refrigeration Manager at a food processing plant I have inherited an oil pot issue in our freezer our accumulator oil pot has been clogged for the past few years the last manager never did any with it his solution was to drain oil from the evaporators in the freezer when our temps start to rise has anyone else ran to an issue with a plugged oil pot and how did you fix the issue

[MrFreez717]

I installed a new oil pot for a customer several years ago and heard back that he could not get any oil out of it. Went to investigate and confirmed that, with inlet and vent valves open, he could open the outlet isolation and deadman valves and nothing would come out. System was under about 30 psi positive pressure. Turned out the brand new outlet isolation valve (3/4" Danfoss angle valve) was jammed shut, regardless of stem position. Appeared to be a manufacturing flaw. Replaced that valve and all was well.

If your troublesome oil pot is actually inside the freezer, it is possible that a combination of low pressure and very thick oil is making it impossible to drain. Do you have any way to warm up the oil pot before the draining process?

MrFreeze717

[NH3-Iceman]

I installed a new oil pot for a customer several years ago and heard back that he could not get any oil out of it. Went to investigate and confirmed that, with inlet and vent valves open, he could open the outlet isolation and deadman valves and nothing would come out. System was under about 30 psi positive pressure. Turned out the brand new outlet isolation valve (3/4" Danfoss angle valve) was jammed shut, regardless of stem position. Appeared to be a manufacturing flaw. Replaced that valve and all was well.

If your troublesome oil pot is actually inside the freezer, it is possible that a combination of low pressure and very thick oil is making it impossible to drain. Do you have any way to warm up the oil pot before the draining process?

MrFreeze717
Yes we run between 1 psi and 1 inch of vacuum and we have a heater plumbed into the oil pot and have changed the heating element we run -20 freezer the eq line on the oil pot doesn’t have an isolation valve we do have an oil still and pump out system nice thing to have my last job we hand to fill up 5 gal bucket of ammonia oil and run hoses for pump-outs

[RANGER1]

In some cases pressuring oil pot with nitrogen to push up lines can clear.
obviously do not over pressurise components.
otherwise pump out & investigation to find blockage & clear.

[MrFreez717]

If you have no isolation valve in the equalizing line, and you run your system around 0 psi, then there is no way to increase pressure in the oil pot above atmospheric pressure and you will always struggle to get anything to drain out of it. Since the atmosphere is also at 0 psi(g), the only driving force you have is gravity, and that may not be enough in a small oil pot. It also means you cannot externally pressurize the oil pot with nitrogen.

MrFreez717

[NH3-Iceman]

If you have no isolation valve in the equalizing line, and you run your system around 0 psi, then there is no way to increase pressure in the oil pot above atmospheric pressure and you will always struggle to get anything to drain out of it. Since the atmosphere is also at 0 psi(g), the only driving force you have is gravity, and that may not be enough in a small oil pot. It also means you cannot externally pressurize the oil pot with nitrogen.

MrFreez717

The old timers say that they used to just get a small amount of oil out then one day it stopped. There was some suggestions thrown around that we pull it down and cut into the line to add a valve so we can build pressure in the oil pot and so we can actually drain oil from the pot. but i am not sure how i feel about that because there has to be a fare amount of oil setting in the bottom of the vessel and in the eq line but there isnt another option is there?

[MrFreez717]

I would advise pumping out the LPR and adding an isolation valve to to the equalizing line, plus a provision to heat the oil pot (electric heater or hot gas connection). Then you will at least be able to drain from it.

You may already know this, but per IIAR2 and ASHRAE 15 pressure vessels must be located in machinery room spaces with ventilation, fire-rated construction, etc. So the REAL solution would be to demo the LPR in the freezer and put it in a more appropriate location. But that's a big pill to swallow...

MrFreez717