Process for the normal shutdown of a compressor
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Taking the speed-regulating type as an example, (1) for a normal shutdown of the compressor, what is the sequence for reducing the speed, fully opening the anti-surge valve, and closing the outlet check valve? (2) Does reducing the speed mean lowering it to the lowest operating speed?
1 Regarding the issue of rotational speed, it is necessary to consider the operating conditions and the characteristics of the compressor before discussing it; for example, when the compressor has a flexible rotor as part of its rotating machinery structure, the critical speed issue must be taken into account； When reducing the speed, the relationship with the system back pressure is taken into account to prevent backflow and similar issues. Therefore, it is necessary to clearly understand the meaning of the minimum operating speed. 3 If only mechanical factors are considered, the power supply (electricity or steam) is simply cut off to stop the machine; the control system automatically activates the drain valve and shuts off the check valve. Lubrication should not be stopped until the rotation speed drops to zero
Basic shutdown sequence for centrifugal pumps: 1. Fully open the anti-surge valves at each stage; 2. Close the inlet and outlet valves； 3. Reduce the speed of the drive turbine to the lowest limit of the speed control range ； 4. Press the stop button
Are the inlet and outlet valves closed at the same time? There is still a sequence
After the anti-surge valve is fully opened, the outlet valve should generally be closed first to prevent gas backflow, as the outlet check valve may experience internal leakage.
For air compressors, the anti-surge valve is used for venting; by closing the inlet valve and then reducing the speed to shut down the compressor, it can no longer draw in air