Regarding the operating mechanism of the inlet and outlet valves of the air compressor

This is correct. Firstly, it applies to piston compressors: the inlet can withstand vacuum conditions, but the outlet cannot handle extremely high pressures. In the event of an issue with the instrument air supply while the compressor is still running, if the inlet is closed and the outlet is opened, there is no risk of damaging the equipment. Do you understand? If not, feel free to ask for further clarification

Hello, thank you for your guidance. May I ask if the rich gas compressor in our catalytic unit is a centrifugal compressor, and whether the inlet butterfly valve operates in the wind-on or wind-off mode? Are the outlet gate valves operated by air or by pressure? Why?

Hello, regarding centrifugal compressors, there is a check valve in front of the outlet gate valve; this valve is a air-shut valve. What is the function of each, namely the inlet butterfly valve and the outlet gate valve? Which configuration is safer?

In centrifugal systems, the outlet valve is typically operated by air pressure; a certain backpressure is required to allow air to flow through it. The inlet valve is also usually operated by air pressure, while the reflux valve is operated by air pressure in the opposite direction. In the event of a failure in the instrument air supply, both the inlet and outlet valves close, while the reflux valve opens. Some designs take into account the surge flow rate of the centrifuge when determining the opening degree of the reflux valve.

No, the compressor does not stop when the purification air flow is halted. The outlet gate valve should be opened to allow air to pass, the inlet butterfly valve should be closed, the check valve should also be closed, and the inlet valves for the large and small flares should be closed as well. This ensures the safe operation of the unit. If the inlet butterfly valve is left open, negative pressure will be applied to the inlet of the centrifugal compressor, which can damage the unit. That’s how I understand it； I’m not sure if it’s correct; I would appreciate your guidance!

No, the compressor does not stop when the purification air flow is halted. The outlet gate valve should be opened to allow air to pass, the inlet butterfly valve should be closed, the check valve should also be closed, and the inlet valves for the large and small flares should be closed as well. This ensures the safe operation of the unit. If the inlet butterfly valve is left open, negative pressure will be applied to the inlet of the centrifugal compressor, which can damage the unit. That’s how I understand it； I’m not sure if it’s correct; I would appreciate your guidance!

There is a common concept: in non-varying-frequency centrifugal fan and pump systems, the flow rate is adjusted by controlling the opening degree of the outlet valve. At startup, open the outlet valve fully; open it after normal startup. When shutting down, close the outlet valve first, then the inlet valve. (There are many old posts on the forum that explain it in detail.) I didn’t quite understand the meaning of this post; it should be discussing the control method for the pneumatic valves at the inlet and outlet of the centrifugal compressor, right? With these basic concepts, my understanding is that the inlet control valve of the fan operates in air-shut mode (it opens when the instrument air supply is cut off), while the outlet control valve operates in air-open mode (it closes when the instrument air supply is cut off). (In the gas transmission system, it is prohibited to close the inlet valve of the compressor during operation, in order to prevent negative pressure from drawing in air.) . . ）