Diagnosis of abnormal noises in screw refrigerators
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Machino of Maekawa: refrigerant is R404A, rotation speed is 4200 r/min, inlet pressure is around 0.4 bar, outlet pressure is around 12 bar, suction temperature is around -32°C, and exhaust temperature is around 45°C. The machine does not run continuously; it starts and stops automatically based on set conditions – presumably once every hour. During operation, there are occasional harsh screeching noises, which usually last for short periods; these noises occur almost every time the machine starts, but they happen intermittently during operation as well. The noises also occur intermittently before the machine shuts down. What could be the possible causes of this? The oil and refrigerant were replaced just half a month ago :(
As a supplementary note, the machine was manufactured in April 2019, and its total operating time is 2700 hours+
Does it start under load every time you turn it on, and where does that screeching sound come from?
It is likely that the lubrication effect during operation is poor, causing the male and female screws to engage directly without any lubricant; the dry friction between the metals generates a screeching sound.
There might be an issue with the fuel supply; check it out.
Mm-hmm, okay, thank you. I’m about to check the oil circuit
It’s pretty harsh to hear, and it’s hard to tell from where the sound is coming from; however, it’s almost certain that it’s coming from the compressor itself, not the motor
1. There may be a problem with the check valve at the inlet and outlet. 2. Is there liquid present at the inlet when the compressor starts up?
Is it the sound of liquid slugging? I’m using a screw compressor with ordinary refrigerant, and it makes a rather sharp noise when it’s turned on; there’s no such noise at other times