Bellows-sealed control valve, pneumatic diaphragm control valve
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Recently, my company needs to purchase a batch of valves, including diaphragm-sealed control valves and pneumatic diaphragm control valves. They seem quite unfamiliar; what are the considerations involved in choosing between these two types of valves? :o
Pneumatic diaphragm bellows control valves offer reliable sealing performance, preventing waste caused by leaks of the medium as well as environmental contamination that could harm the health of operators. Therefore, it is particularly suitable for regulating highly toxic, valuable, volatile, and permeable media, as well as for applications involving pipeline vacuum. The structural principle of pneumatic diaphragm corrugated seal adjustment is a variant of pneumatic diaphragm single- and double-seat control valves. It consists of a gas diaphragm actuator and a bellows-sealed valve. Inside the upper valve cover of the valve section, there is a bellows component that isolates the medium from the outside environment and ensures that the valve stem can move up and down. In addition, there is also a PTFE \"V\"-shaped packing seal at the upper end of the upper valve cover, which serves as a secondary seal in case the bellows component is damaged. A pressure gauge is also installed on the outer wall of the upper valve cover to indicate the pressure outside the bellows; if the bellows are damaged for some reason, the reading on the pressure gauge will change accordingly. Principle: When the actuator chamber receives a pneumatic signal, it causes the diaphragm and membrane spring to compress, which in turn pushes the push rod, valve stem, and valve core, thereby changing the flow area between the valve core and the valve seat and altering the flow rate in order to adjust the process parameters. Pneumatic diaphragm control valves come in many different types depending on their structure and application. For high-pressure oxygen applications, positive-acting, straight-through, single-seat type proportional control valves are commonly used; their standard designation is ZMAP. These valves consist mainly of an air chamber, a diaphragm, a thrust disc, springs, a push rod, and an adjustment nut. It consists of a valve position scale, valve stem, valve disc, valve seat, packing box, valve body, valve cover, the valve itself, and brackets. Working principle: When a signal pressure of 0.02–0.10 MPa is applied to the air chamber, a thrust is generated by the diaphragm, causing the thrust disc to move downward and compressing the spring. This in turn drives the push rod, valve stem, and valve core downward, causing the valve core to move away from the valve seat and thus allowing compressed air to flow through. When the signal pressure remains constant, the valve stays at a certain opening degree.
In petrochemical systems, control valves with bellows seals are generally used for regulating toxic and highly toxic media. To prevent any leaks from occurring. Ordinary control valves may leak through the packing gland. Whether it is a normally sealed or diaphragm-sealed control valve, its actuating mechanism can be a pneumatic diaphragm type.
Could some senior student send me a diagram of the internal structure of a control valve?
I happen to have information on this topic; you can add me! QQ: 928976489
A bellows control valve is a control valve equipped with bellows, primarily used to prevent the leakage of hazardous corrosive media; when selecting such a valve, it is necessary to pay attention to the material used, taking into account the corrosiveness of the medium. A pneumatic diaphragm control valve is one whose actuator is a pneumatic diaphragm type; there is nothing special to note.