Hello

At one of my customer system we have two hermetic ammonia recirculation pumps install on a horizontal expansion receiver. One is the backup of the other. The system is operating since three months, the first pump is always calvitating compare to the other is never calvitating. I am wondering why.

The pump could calvitate more than 6 times in a hour at least once every two weeks. During a day we occasionnaly see the pump calvitating. My refrigeration capacity is mainly stable, because it is a holding freezer at -12dF.

When we operate with the other pump it is never calvitating, same system, same receiver, only opposite connection.

The pump were design at a 3ft NSPH and we always have a 4ft NSPH, the amps of the motor 3Hp is 1amps below the motor maximun design. My piping design are the same. But one maintain a better pressure rise than the other one. They are both new pumps. A pump guardian is install on each pump.

We opened the pump which is always calvitating and iis seems ok.

My operating system is at 2inHg succion pressure
and at 160psig high pressure.

kathleen, P. eng

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