Problems with self-acting valves

A so-called “self-acting valve” is a valve that uses the pressure, temperature, and flow force of the medium passing through the valve itself as an energy source to operate it automatically, without the need for any external power supply. I have only come into contact with the self-acting control valves produced by \"Wuzhong Instrument Factory\" and those made by Shanghai Biaobei Valve Factory; they seem okay, but I haven’t used them very often, so I don’t have many opinions to share. When Wu Zhong went to the factory at that time, he saw a self-acting control valve that was over 2 meters tall – much larger than mine. It seemed to be of good quality in terms of manufacturing, but it’s not clear what its performance is like. :)

Why would the landlord choose domestic options rather than foreign ones? The springs produced domestically are not very precise, and their prices aren’t much higher either!

“A “self-acting control valve” gives me the impression of being a safety valve. There is one at the outlet of stage 1 of the nitrogen turbine compressor in my branch office; it activates automatically when the pressure is high. However, it has an advantage over safety valves: it can be adjusted according to the pressure conditions, thereby stabilizing the pressure in the pipeline. But the selection is very important; for example, whether there is atmospheric pressure or pressure behind the valve! This is very important; initially, when the nitrogen turbine in my branch office was started up, there were issues due to insufficient monitoring (the flow meter was located on the outlet pipeline of the second stage), and it was because of valve leakage. After reviewing the original data, it was found that the valve type had been selected incorrectly; a valve with normal pressure on the downstream side should have been used. Instead, a valve with pressure on the downstream side was chosen, resulting in a large pressure difference between the two sides, which caused the valve to open on its own. A full two-stage surge test cannot be carried out. . Later, a new one was installed, and this time there were no leaks. However, the surge curve of the compressor can no longer be used; all the automatic control valves are controlled by the PLC, and their switching speeds are not fast enough to meet the current operating conditions. During testing, the system shut down twice due to high outlet pressure. As a result, the compressor has to be placed back in its original position, and it’s necessary to wait for the manufacturer’s technicians to conduct another surge test and adjust the switching speeds of the return valve and guide vanes. I earnestly ask those who have read this post to keep these lessons in mind! Valve selection is very important! Especially for self-acting valves, it is essential to accurately determine whether backpressure is required!