Definition of valve foundation
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I don’t understand the definitions of control valves, quick-acting valves, and emergency cut-off valves; I also don’t know what the relationship between them is, or which one includes the others. Please ask that expert to give some guidance.
A control valve is one that comes with a positioner; an input of 4-20mA corresponds to a valve opening degree of 0-100. The card used in the DCS system for this purpose is an AO analog output card. A shut-off valve, on the other hand, has an electromagnetic valve built into it, and the opening and closing of the valve are controlled by whether power is supplied or not – the opening degree is either 0 or 100. The card used in the DCS system for this type of valve is a DO digital output card, which is usually connected to a relay for normal-open operation. Well, that’s generally how it works; feel free to add any further details…
Broadly speaking, cut-off valves can also be called control valves.
Control valves are a type of valve; quick-cut valves and emergency shut-off valves also belong to this category. Control valves are used to regulate flow, while quick-cut valves, emergency shut-off valves, and shut-off valves can only be in either an open or closed state
The cut-off valve has only two positions: open and closed
All three fall under the category of control valves. The quick-cut valve and the quick-break valve have only 2 feedback options, allowing them to operate in either fully open or fully closed state, with rapid response. Although control valves can also operate in fully open or fully closed positions, they take longer to respond, and their sealing performance is inferior to that of the first two types of valves.
Previously, on the drawings from the design institute, cut-off valves were classified under control valves. But regarding your comment above now. . . . .