High Level alarm / low level alarm for Low Pr. receiver

Recently we have done a ref system with low pr receiver. It is also having Ammonia Pumps etc. Incidently durign commissioning stage we came across a situation wherein Liquid was coming back to compressors. It had do with High level cutout being faulty in the low pr. receiver. We were wondering on more safety for this particular issue. I came across very good suggestion in Industrial Refrigeration handbook by Wilbert Stoecker. I though I must share this point with the forum. Ofourse many may be using this extra safety though.

Getting liquid back into compressors is serious. How did it happen?

Since you did not mention what the suggestion was from the book, I am assuming you mean the use a mechanical float switch to shut down the compressors.

Capacitance probes are nice, but I always prefer to have a mechanical float switch for protecting the compressors. The floats rarely fail so I think this is a good protective measure.

Hi, smpsmp45 :)

Quote:

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Originally Posted by US Iceman

Capacitance probes are nice, but I always prefer to have a mechanical float switch for protecting the compressors. The floats rarely fail so I think this is a good protective measure

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agree with this....:D

...but you can have a problem with suction headers (wrong slope, wrong connections...etc..and you can collect a lot of liquid within and suddenly return to compressor causing a big headache...

...sorry, but I have to ask, is this plant one of Allana cold stores in Mumbai...

....before 25 years I had this situation (2times:eek: before we discover what and why/but that is another long story), with emergency stop of the chemical process plant with cost of about 120000DEM (60000 Euro today) each emergency stop:o....the good luck was because we (ex Yugoslavia) in that time were socialist country with "collective responsibility;)" I do not want to imagine court processes and compensation today...

coming back to your problem....within new compressors control cabinet there is always suction temp probe where you monitor suction superheat (SSH) and stop compressor/s automatically if become to low and before liquid return....

Best regards, Josip :)

The good old days Josip ;)

i look at this problem in a very much different perspective.

my opinion:
1] liquid floodback or floodstart happens may be the cause of insufficient evaporation velocity for the refrigerant in the low receiver.

2] possibly, the normal liquid level is arealdy high (referring earlier point) & when fluctuations in liquid return volume, new level is beyond tolerable level and carry back via suction pressure.

3] construction of lo receiver is also very important. there are few important features which are intentionally fabricated inside the receiver to handle such issues.

....