The issue of compressor reversal
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What are the characteristics of reverse rotation in a compressor during shutdown, and what are its hazards?
I’m not too sure about the other aspects, but screw compressors sometimes reverse rotation when stopped, mainly due to backflow of air flow. The engine speed **increases**, resulting in loud airflow noises; this can easily cause damage to the machine, as it exceeds the operating requirements for seals, bearings, and other components as designed for the machine.
The reverse rotation of the compressor after it stops operating is caused by a fault in the compressor’s outlet check valve; this results in high-pressure gas from the outlet flowing back, causing the compressor to rotate in the opposite direction. Such reverse rotation can damage the mechanical seal or the bearing shells. Motor drive may also cause damage to the motor.
Ours is a centrifugal compressor, driven by a steam turbine. There is no check valve at the outlet; solenoid valves and an outlet shut-off valve are located on the outlet pipeline. The cut-off valve is at the front, and the solenoid valve is at the back. I mainly want to ask what signs can indicate that a reversal has occurred? Thank you! ! !
In the case of motor-driven systems, the motor shaft bearings can get damaged
It’s mainly due to pressure imbalance; when pressure is released, some of it is released while some remains, which makes reversal easy to occur.
The final cause of the inspection was that the shut-off valve at the exit was not closed in time when parking. Reversal caused by the backflow of gas.
If the compressor is lubricated by a shaft head pump, the main risk of reversing its operation is the destruction of the shaft bearings.
The hazard of reversal is that it can easily damage the oil film, leading to damage to the bearings or the rotor journals; furthermore, it can also cause damage to the mechanical seal!
When the compressor’s speed drops to zero and then suddenly shows that it is moving again, it is very likely that the rotation direction has reversed. If a reversal occurs, the sealing system will definitely be destroyed!