Could someone with expertise please explain these types of valves? Thank you!

Based on your description and pictures, it can be inferred that the valve is a pneumatic on/off valve with a handwheel. It falls under the jurisdiction of instruments. Two points: 1. Given that it is an emergency pressure relief valve as described by you, whether a handwheel should be installed is something that needs to be discussed. According to the HG_T20507-2014 Standard for the Selection and Design of Automation Instruments issued by the Ministry of Chemical Industry, safety interlocks used for process production purposes, which are intended for emergency shutdown of valves, should not be equipped with handwheels. ”The selection guidelines provided by the design institute also state the following: “Handwheel mechanisms are suitable for use in the following situations: a) Control valves or shut-off valves that do not have shut-off valves or bypass valves installed.” However, handwheel mechanisms shall not be provided for emergency shut-off valves used for safety interlocks or control valves installed in hazardous areas where access is prohibited. Unless the PID indicates that its operability is higher than its safety ； ”2. Since this valve already has a handwheel and is used for emergency pressure relief, it is recommended to set it to automatic mode and lock it in place; if possible, remove the handwheel as well. Avoid misoperations. How to switch between manual and automatic mode varies by product; please refer to the instructions.

These valves are pneumatic valves; the lower part constitutes the valve itself, while the upper part is connected to a pneumatic actuator, which is activated by electrical signals. When manual operation is required, it can be controlled using an on-site handwheel. Just check the instructions – it needs to be implemented according to the actual setup requirements on site; it can also be operated via a switch (quick-cut valve), or through digital control.

There was once a situation where, due to the extremely cold weather, the automatic emergency pressure release mechanism did not activate; therefore, an manual emergency release was used. It seems that the handwheel is indeed quite useful!

There was once a situation where, due to the extremely cold weather, the automatic emergency pressure release mechanism did not activate; therefore, an manual emergency release was used. It seems that the handwheel is indeed quite useful!

This is a pneumatic valve, which consists of a valve body, a cylinder, and a solenoid valve. The principle behind its operation is that the solenoid valve injects gas into the cylinder, causing the piston inside the cylinder to move; this movement in turn drives the valve body to open or close

It should be a hydraulic valve with a manual switch