Regarding the startup process
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“Before starting, close the inlet and outlet, open the return valve; there is no pressure in the pipeline and no load. Start the motor – no abnormalities occur after startup. Then open the inlet to begin pumping. Once the pressure at the primary inlet reaches equilibrium with that of the system, open the outlet and close the return valve, after which a load is applied. ”Starting of reciprocating compressors – Taken from the forum: https://bbs.hcbbs.com/thread-1292536-2-1.html Question: I would like to ask whether this process is applicable to centrifugal or axial flow compressors as well? Also, in the case of an air compressor without a return pipe, if the inlet valve is closed completely, won’t the compressor create a vacuum?
This is a reply to another post: “Turning on the inlet and outlet valves when starting the fan, and then gradually opening the outlet valve, is done to protect the fan; if the motor has a very high power rating, it also helps to maintain stable operation of the power grid.” So, how are the opening and closing of the inlet and outlet valves defined before starting?
Neither screw nor centrifugal air compressors will cause vacuum formation (in the absence of a return pipe); even with all valves closed, 10% of air intake is ensured to prevent vacuum formation in the unit, as this has been taken into account by the manufacturers during design
If it is a motor-driven compressor with adjustable speed, does the inlet valve also need to be closed before starting? The project I’m currently working on involves a 3-stage centrifugal air compressor driven by an engine; it has only one exhaust valve. The idea is to keep the inlet valve fully open, the outlet valve closed, and the exhaust valve fully open. Once the compressor reaches its rated speed, the exhaust valve is closed. When the outlet pressure exceeds the pressure in the pipeline system, the outlet valve is opened. After the exhaust valve is fully closed, the speed of the compressor is increased again. Is there anything wrong with this procedure? I work in control systems; it’s my first time shutting down a compressor, and I’m not very familiar with the process
Whether it is steam-driven or electrically driven, the control system remains unchanged; with steam-driven systems, there is simply a critical speed, which can generally be avoided
Learned: handshake. Thank you
Even if the pressure on the system’s official website is higher than the pressure at the compressor outlet, the relief valve will not close immediately; instead, both the inlet valve and the relief valve operate together to prevent waste of compressed air. The change in speed will not be significant, as too large a change could cause surging in the centrifugal air compressor or nitrogen compressor
Don’t units with adjustable speed regulate the air supply pressure through speed? Moreover, in the information I’ve gathered, the start-up of centrifugal air compressors with adjustable speed always involves the inlet valve being fully open. One more question: when you mention the inlet valve, do you mean the inlet guide vane or the valve located at the front of the unit? In air compressors with generally adjustable speed, the inlet is directly connected to the air filter, without any valves. .
By IGV, I mean the inlet guide vanes. Centrifugal air compressors have only inlet guide vanes, and outside these vanes is the air filter. Centrifugal air compressors are inherently speed-type machines; however, under normal operating conditions, the speed cannot change rapidly, otherwise surge will occur.