Choking in Refrigeration Plant

Hi guys, we have been having a huge problem in our refrigeration plant.
i am not the engineer so i don't know much about technically but i will writer as much as i know about the problem of this plant.
We have a ***** gas based Refrigeration plant. Compressor pumps the ***** gas and gas runs through copper pipes from condenser then filter and then it goes to the tank which contains salt water and there are copper pipes inside it and gas runs within the copper pipes.
Coming straight to the point.
we are facing a huge problem right now the refrigeration plant it getting choked when it maintains the required temp and after that when we shut down the whole system for about 10 hours or more and restarts it then it works again, then after some time same problem happens again.
Our engineer trying everything in order to fix it but couldn't fix it.
he cleaned the whole plant many times with dry nitrogen gas using menthol liquid in copper pipes there is no leakage in the pipes and the pipes looks clean. there is little carbon which comes out within the copper pipes when we clean them using nitrogen gas. we changed the compressor, filter as well as expansion valve but the problem is still the same.
Can anyone tell us what could be the problem?
Is it happening because of the ***** gas or because of the pipes?
Any help would be greatly appreciated.

Maybe moisture in the refrigerant or worse a small water leak from your tank, you could get a refrigerant sample checked.

.

Are you using the same refrigerant or did
you replace the refrigerant for new each
time you cleaned the system?

Rob

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Quote:

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Originally Posted by Gibbo

Maybe moisture in the refrigerant or worse a small water leak from your tank, you could get a refrigerant sample checked.

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Thanks for reply i appreciate it. While cleaning up the system we can see few little drops of water coming out the refrigerant lines. What could be the reason? And for some times refrigeration system works for 3-4 days without any problem. I think it can't happen if there is water leakage in the tank? what do you think?

Quote:

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Originally Posted by Rob White

.

Are you using the same refrigerant or did
you replace the refrigerant for new each
time you cleaned the system?

Rob

.

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Thank you for the reply i appreciate it. We are using the same refrigerant after cleaning up the system. can you please tell me how we can find that there is moisture in the refrigerant and now it cannot be used in the system?

Expansion valve will shut down with moisture in the system. Check compressor oil for colour change.
Moisture in the refrigerant freezes at Expansion valve outlet when your plant is working.
Install a LARGE capacity liquid line drier and a suction line drier while your at it.
If there is a liquid solenoid valve for pump down, make sure your Low pressure switch is calibrated to turn off compressor above atmospheric pressure.

It should have a HP/LP anyway. What type of gas are you using?

As the others say get a sample analysed of the refrigerant and get an oil analysis.
You may have incorrect oil or contamination causing foaming or poor miscibility.

Quote:

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Originally Posted by mikeref

Expansion valve will shut down with moisture in the system. Check compressor oil for colour change.
Moisture in the refrigerant freezes at Expansion valve outlet when your plant is working.
Install a LARGE capacity liquid line drier and a suction line drier while your at it.
If there is a liquid solenoid valve for pump down, make sure your Low pressure switch is calibrated to turn off compressor above atmospheric pressure.

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Thanks for the reply.
we are using liquid line drier. and in our refrigeration plant we are using R134a gas.
Can you tell me is it necessary to use oil separator. and if there is moisture in the plant do we have to clean the oil separator as well?

Quote:

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Originally Posted by hookster

As the others say get a sample analysed of the refrigerant and get an oil analysis.
You may have incorrect oil or contamination causing foaming or poor miscibility.

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Thanks for the reply.
The sample of the refrigerant is sent for the analysis. Now we are going to change the refrigerant as well as the refrigerant oil.

the Refrigeration Oil that we are using with R134a is ZEROL 200TD.

With out looking at complete plant specification i.e compressors etc.
The alkylbenzene oil would not be my first choice! I would go back to plant manufacturer to confirm why this choice of oil was made.

I would probably have gone for a POE but as stated before a lot more detail on your plant would be required for an informed choice.

does his vac pump work correctly- fit a torr gauge at the furthest point of th vac pump- check for backdrops when vac pump isolated, maybe triple vac- increase surrounding air temp to improve vaccing process

But this ZEROL 200TD alkylbenzene oil is recommended by Plant Manufacturer. What do you suggest for R134a?

Quote:

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Originally Posted by install monkey

does his vac pump work correctly- fit a torr gauge at the furthest point of th vac pump- check for backdrops when vac pump isolated, maybe triple vac- increase surrounding air temp to improve vaccing process

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Thanks for the suggestion we will try that?

I agree with the other posters, I think you have to start afresh.
Remove refrigerant, pressure test and repair any leaks, remove oil from compressor, flush system with a flushing agent, triple evacuation to 250 - 500 microns, new oil, new refrigerant.
I tend to agree with Hookster about the oil, just remember POE oil is very hydroscopic.
Paul

Quote:

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Originally Posted by PaulZ

I agree with the other posters, I think you have to start afresh.
Remove refrigerant, pressure test and repair any leaks, remove oil from compressor, flush system with a flushing agent, triple evacuation to 250 - 500 microns, new oil, new refrigerant.
I tend to agree with Hookster about the oil, just remember POE oil is very hydroscopic.
Paul

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Thanks for the suggestion. Now we are following this procedure. I hope everything will be fine now.

put your system minimum 24 h in vacuum to remove all moisture

Sounds like a busted tube. This is a brine chiller?
R-134a is almost always POE. If you're having this kinda trouble you might need an eddy current test performed.

suggest triple vacuum to drive out the last trace of moisture from system before re-commissioning.

might be moisture of the refrigerant is not sufficient, change it and try

Quote:

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Originally Posted by airtrackinc

might be moisture of the refrigerant is not sufficient, change it and try

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Moisture of the refrigerant???? Hmmm

Just make sure all solenoid valves are open while cleaning & vaccing the system! It's an easy thing to overlook. ;)

From looking at the original post it suggests that the system stops working, then if it is stopped for 10 hours it starts working again. Is this without any intervention on the refrigerant circuit? If so I would suggest checking the Brine concentration. If the concentration is too low (or too high) this can cause partial freezing around the pipes causing low refrigerant pressure which could appear to be blocking of the expansion valve.