State of the suction and discharge valves when a reciprocating compressor is shut down
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Our Shenggu compressor model 4M5O shuts down at 0 load. Under load, the intake valve is fully open while the exhaust valve is closed. After shutting down, in order to unload the system, the load is increased to 100%; at this point the exhaust valve opens. But is the intake valve still open? Who can explain this?
Just look at the operating cycle – a set of intake and exhaust valves cannot be opened or closed simultaneously.
After shutting down the machine, close the inlet and outlet valves, open the vent valve, and set the unloader to zero load.
This answer is great! There’s no need to worry about opening and closing the valve anymore! :lol
We return one for one, two for two, three for three, stepping back gradually without releasing pressure, with hydrogen as a backup. By the same logic, during nitrogen displacement at zero load, how can displacement take place with the exhaust valve closed?
To address the original poster’s question: First, based on your description, the press is equipped with a unloading device. If it operates at 100% load when shut down, the situation is the same as when there is no unloading device; the air valve is one-way and relies on pressure differences to allow air intake and exhaust
Pressure difference is key! ! That’s all I can say·
The last edit to this post was made by space ★ Xuan on 2015-11-1 at 15:15. Let me answer why the value should be set to 100% after shutdown. As the original poster said, the adjustment of the compressor is done via the inlet unloader; under normal 100% operation, the suction and discharge valves remain in their natural position, with the differential pressure switch playing a role in this process. A 0% load is achieved by using a unloader to force the inlet valve open; when the machine is shut down and set to 100% load, the suction valve remains in its natural state. If the machine stays at 0% load for an extended period after shutdown, the spring of the inlet valve will be under pressure continuously, which over time affects the elasticity of that spring. It’s simple: when a spring is under pressure for a long time, it gradually loses its elasticity. Therefore, for normal reciprocating compressors that are shut down or in standby mode, the load is set at 100%. This exhaust valve has nothing to do with it; in this situation, the exhaust valve doesn’t have a unloader clutch, so it doesn’t function properly
Don’t exhaust valves open and close based on pressure difference? The exhaust valve shouldn’t have settings like opening under pressure – how does it get opened?