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Thread: Check valve selection
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31-08-2010, 08:59 AM #1
Check valve selection
There is interesting problem of check valve selection in parallel working compressors. I select check valve for liquid line (condenser/receiver) for total compressors capacity, but when some compressors not work there are low opening degree and there is a risk of instabillity of working, because the flow of refrigerant is to small to open this valve. Velosity in thise pipe must be no more then 0.5 m/s, if I select more smaller valve then it will open on minimum compressors capasity but on maximum capasity velosity of liquid will be 1.4 m/s. Could you tell me how can I solve this problem?
In some places will have to think ...
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31-08-2010, 09:09 AM #2
Re: Check valve selection
Many check valves start opens at 0,1 bar or less. So in this particular case if you have a column of 1 m » 2 m of liquid (depending of the refrigerant density) between condenser outlet and receiver it will no problem.
To make progress is never good enough, I want to do better and better and better
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31-08-2010, 09:40 AM #3
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31-08-2010, 09:53 AM #4
Re: Check valve selection
Do you mean on the discharge pipe of each compressor?
To make progress is never good enough, I want to do better and better and better
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31-08-2010, 10:13 AM #5
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31-08-2010, 10:52 AM #6
Re: Check valve selection
In that case is more complicated...but depending the number of compressors and/or its capacity stage may have an unique valve that accept as minimum capacity 15-20% without generate high pressure drop ate 100%.
If there is only one rack with one general oil separator I don't see the necessity of install check valve albeit many plants have it.To make progress is never good enough, I want to do better and better and better
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31-08-2010, 11:05 AM #7
Re: Check valve selection
In some places will have to think ...
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31-08-2010, 11:53 AM #8
Re: Check valve selection
The refrigerant can be evaporated by electric heat around the oil tank; or shut off by electric valve the oil return to the oil thank and heating the oil separator or give a time to open the EVR to oil tank after the compressor working about 10 min.
To make progress is never good enough, I want to do better and better and better
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31-08-2010, 12:09 PM #9
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31-08-2010, 02:11 PM #10
Re: Check valve selection
You can buy it separate from the oil separator. It is an electric strap that is put around the oil separator. It is sold on PECOMARK, DISCOLIS, or other suppliers.
Or use a timer as I explain aboveTo make progress is never good enough, I want to do better and better and better
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31-08-2010, 09:13 PM #11
Re: Check valve selection
Have you looked at Danfoss check valves as I know your predicament for selection can be difficult to avoid fluttering.
On industrial we use duo check valves which handle your circumstances but of course you may not want flanges .
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01-09-2010, 01:49 AM #12
Re: Check valve selection
How sensible it is to have one check valve in the discharge line for parellel compressor operation? Won't it hamper the compressor capacity?
regardsBR
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01-09-2010, 05:27 AM #13
Re: Check valve selection
I'd suggest using one check-valve per compressor - correctly sized to suit compressor delivery.
Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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