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View Full Version : Help needen! Temperature changes as the second compressor starts!







Oscar1977
29-05-2013, 10:45 AM
We have Linker Cooling system with Vilter XL compressors in our beverage filling plant.
The problem the we face is that, we have two Vilter ammonium compressors, during the winter time, one is enough to provide necessary cooling it provide constant cooling, but during summer time we operate both but what happens is that during the normal operation production temperature suddenly increases and decreases in the beverage tank which is cooled by the refrigerant, we are sure that this is occurring when the second compressor is also loading. Do you have any idea about this problem. Attached you can find the drawing of the cooling system. Your suggestions will be very much appreciated. Thanks a lot.

RANGER1
29-05-2013, 09:35 PM
Oscar, Its all about knowing what compressors need to run for the product you are producing. Knowing that & say you need 2 compressors running, then you have to design control system to suit. Basically if 2 need to run, then they have to load/unload equally to keep them both running all the time. If example they are 2 X 454XL Vilters compressors then it would be start first compressor load to 50%, then start second compressor & it would load to 50 %. After that both would load /unload together. Note normally in this type of plant the compressors should be able to unload to 0% while running, so unloaders on all cylinders if possible, for any plant production hiccups etc. They normally can run unloaded for maximum of 10 minutes each before you shut it/them down to prevent overheating. Also these type of plants have installed a "false load" valve which is a downstream pressure regulator connected from top of liquid receiver to compressor suction line. This is set slightly lower than compressor unloaders, so to maintain some work for compressors to do when production stops ie hiccup, flavour change etc. Also recommend high discharge temperature/ oil temperature safety protection, compressor oil cooler & limit start timer to protect compressor motor set start to start of 10-15 minutes.

Oscar1977
30-05-2013, 12:17 PM
Hi, Ranger would you please provide your email address, so I can send you images of the pressure controls, I wonder if it is possible to work 50% with this settings. Thank you very much.

Oscar1977
30-05-2013, 01:21 PM
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Oscar1977
30-05-2013, 01:22 PM
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Oscar1977
30-05-2013, 01:23 PM
I have uploaded them all. Would please make your comments. Many thanks

RANGER1
01-06-2013, 08:08 AM
Oskar, probably need a bit more information. The Vilter compressors, how many cylinders are they? Also are they oil or gas operated? Are they energized to load compressor or unload? There is a pressure switch on carbo-cooler set at cut out 45psi 0 deg C cut in 65 psi 7 deg C, is this to close suction line pressure regulator? Normally suction pressure is controlled in carbo-cooler with suction pressure regulator set at -1 to1 deg C to get maximum cooling without freeze up on plates. This valve is not a turn on/off valve(normally). On standby it would have another pressure regulator set at a much higher pressure setting to prevent refrigeration if more than one carbo-cooler on system. The -1 to +1 pilot regulator on main carbo-cooler suction regulating valve could have a solenoid in series with it to turn carbo cooler off, then higher pressure set pilot set a maximum, say 100psi 18 deg C. System would work best if both compressors run together & ideally load share by loading/unloading. Best solution is PLC control with suction pressure transducer. Note also pressure switches scale is only a guide, best to set them exactly with air or dry nitrogen. Pressure switches should be set in correct order controlling approx between -5 to -20 deg C (39 to13 psi). By the way I cannot for some crazy reason space or put things on separate lines when writing a post, very frustrating