I hope an expert can explain the function of the air circuit and accessories of this valve

I can explain point 3 in Figure 3: After passing through the filter-pressure reducing valve, the air supply splits into two paths; one of these paths leads to the valve positioner. This path involves a regular control valve, and its regulation is likely carried out via the DCS system. The other path leads to the solenoid valve; this valve is supposed to be able to be shut off or opened via the SIS in emergency situations. Figure 1 is not very clear; it is presumed to be a pneumatic relay used to accelerate the opening or closing of a valve (the exact technical name is unknown). In Figure 2, only the pipeline entering the cylinder is visible; it’s not clear where the pipeline from the other side comes from

1. 377 can achieve interlocked shutdown, startup, and hold functions through different air circuit configurations; details are provided in the attachment； 2, 2 is a needle valve used to connect the upper and lower air chambers of the cylinder; it opens only when operated using the handwheel and closes during control ； 3. The 3 is an overpressure protection device that prevents the gas source from reaching excessive pressure levels ； The above valves achieve control via solenoid valves, 377, and double-acting positioners, as well as maintaining a safe position during interlock conditions ； There may also be a instrument air storage tank on the gas line. It is recommended that the poster understand the principle of valve operation and find the pneumatic circuit diagram of the valve, as this will facilitate analysis.

The gas-phase refrigerant to the compressor should be the FO anti-surge valve.

I drew a pneumatic circuit diagram based on it; there is no air storage tank on site

Could you, expert, take another look at the air circuit diagram I drew? Thank you

Expert, it’s obvious that the refrigerant flows toward the compressor; please take a look at the circuit diagram I’ve drawn. Thank you

It is a double-acting cylinder; the solenoid valve is used to control its opening or closing in emergency situations, while OUT1 and OUT2 control the upward and downward movement of the cylinder. Personal opinion.

1. According to the diagram you provided, when air is supplied to port 377 via the solenoid valve, ports AB and DE become connected; the output of the double-acting positioner is connected to the upper and lower ports of the cylinder, and the positioner controls the opening degree of the valve properly； When interlocking occurs, the solenoid valve releases air, and BC and EF become conductive; if there is a plug in C\F, the valve maintains its position ； In the absence of a plug, if there is a spring inside the cylinder, the fault position is its extended state ； For details, see the attachment in my previous reply; it contains information on the 377D fault shutdown ； 377L fault lockout ； 377U failure offers three specific gas path connection methods ； 2. According to the on-site markings, it should be a valve for returning the gas-phase refrigerant to the compressor; it should be an FO valve ； The common practice is to use a gas tank, with the gas pipeline connected in a 377U configuration ； 3. If there are still differences between the above analysis and the typical configuration requirements, refer to the valve specification sheet and the pneumatic circuit diagrams in the handover documents, as well as the descriptions of the valve failure locations in the PID diagrams.

Thank you so much; your guidance was really helpful. Thank you for your hard work; wish you a happy life.