Reciprocating compressor issues
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When shutting down a reciprocating compressor, should the inlet and outlet valves be closed first after the load is removed, or should the motor be stopped first before closing the valves? It is hoped that there will be sufficient reasons and criteria to support the answer.
Of course, stop the motor first before closing the valve! The operation manual provided by the compressor manufacturer is the reason and standard. The reason is easy to understand: as long as the motor keeps running, the compressor continues to work. If the outlet valve is closed, it doesn’t have much impact on the unit if the relief valve (or another name for it) remains open. But if the inlet valve is also closed, then the compressor loses its source of gas supply, and it will definitely start drawing negative pressure! Therefore, interlocks are usually installed as soon as pressure is applied. Under normal conditions, if the motor stops, the inlet valve unit will definitely shut down via interlock; if the interlock fails, it can lead to serious damage or even loss of life! ! :L
I strongly agree with what was said above; in any case, for all the compressors I have operated, I always stop them first and then close the valves.
First, shut down the motor; wait until the compressor has completely stopped running, then close the inlet and outlet valves! This isn’t a problem – anyone who has driven a vehicle knows this. It is important to be careful to prevent backflow when stopping. Close the outlet valve. However, check valves are usually available.
I disagree with the opinion above; in fact, a reciprocating compressor does not produce any gas flow when it is under unloading conditions, meaning it is operating at no load. Closing the outlet valve does not increase the pressure, and closing the inlet valve does not cause the inlet to become under vacuum. Of course, in the case of loading and unloading the compressor using circuit control, the principle is the same as that of a unloading valve; even when there is no load, it is possible to turn off the motor power by closing the inlet and outlet valves.
I’m sorry; it should be the opinion from the 4th floor. I disagree with what was said on the 2nd floor, as the view from the 4th floor makes some sense.
The opinion from above makes some sense, but in actual production various factors need to be taken into consideration. If there is a problem with a unloader, even though the unloading switch has released the load, the unloader may still be under load; in such a case it would be dangerous to close the outlet valve first. Of course, a functioning safety valve will provide protection in such situations. Therefore, from the perspective of safe production, the machine should be shut down first before the valve is closed
I agree with what was said on floor 7: if there is a problem with the load carrier, even though the load switch is turned off, the load regulator may not have activated. Closing the outlet valve can then lead to overpressure at the outlet. For safety reasons, it is necessary to take into account the possibility of problems with the load carrier switch. From the perspective of safe production, it is advisable to shut down the machine first before closing the valves. However, when shutting down the machine, it is important to pay attention to the opening degree of each circuit; these should be closed completely to prevent backflow of gas and pressure surges
Compressor manufacturers provide instructions, so take a look at those first. Most reciprocating compressors have bypass circuits, though some do not. Even when such circuits are present, the bypass valves may not be easy to control. Therefore, it is very dangerous to close the valves first before shutting down the compressor. Normally, one should shut down the compressor first, then close the inlet and outlet valves, and finally release pressure by venting the air.
First, open the outlet vent valve, stop the motor, close the inlet valve, close the outlet valve, and then close the outlet vent valve. This is a procedure that must be followed. When driving, the exhaust valve must also be opened first.