As a control component in the fluid conveying system, the valve has the functions of cutoff, regulation, diversion, prevention of countercurrent, pressure regulation, shunt or overflow pressure relief. Valves are classified in a variety of ways, and the following are described in detail from multiple perspectives:
First, classification by function and use
1. Cut-off valve:
– Also known as closed-circuit valve, the main function is to connect or cut off the medium in the pipeline. Cut-off valves include gate valves, globe valves, plug valves, ball valves, butterfly valves and diaphragm valves.
2. Check valve:
– Also known as check valve or check valve, the main function is to prevent the backflow of media in the pipeline. The bottom valve of the water pump suction close also belongs to the class of check valve.
3. Safety valve:
– The main function is to prevent the medium pressure in the pipeline or device from exceeding the specified value, so as to achieve the purpose of safety protection.
4. Regulating valve:
– Including regulating valves, throttle valves and pressure reducing valves, etc., the main role is to adjust the pressure, flow and other parameters of the medium.
5. Diverter valve:
– Including a variety of distribution valves and traps, etc., the main role is to distribute, separate or mix the medium in the pipeline.
Second, classify by pressure
1. Vacuum valve:
– Refers to the operating pressure of the valve below the standard atmospheric pressure.
2. Low pressure valve:
– Refers to the valve with nominal pressure PN ≤1.6Mpa.
3. Medium pressure valve:
– refers to valves with nominal pressure PN of 2.5, 4.0, 6.4Mpa.
4. High pressure valve:
– refers to the nominal pressure PN of 10 ~ 80Mpa valve.
5. Super high pressure valve:
– Refers to the nominal pressure PN≥100Mpa valve.
Third, according to the working temperature of the medium classification
1. Ultra-low temperature valve:
– For medium operating temperature t<-100℃ valve.
2. Low temperature valve:
– For medium operating temperature -100℃≤t≤-40℃ valve.
3. Normal temperature valve:
– For medium operating temperature -40℃≤t≤120℃ valve. It is also said that the medium operating temperature range of the normal temperature valve is -29℃
4. High temperature valve:
– For medium operating temperature t>450℃ valve. It is also said that the medium working temperature of the high temperature valve t≥450 ° C (source: mobile sohu).
Fourth, according to the mode of operation classification
1. Automatic valve:
– No external force is required to drive, relying on the energy of the medium itself to make the valve operate, such as safety valves, pressure reducing valves, traps, check valves, etc.
2. Power drive valve:
– It can be driven by various power sources, including electric valves (driven by electricity), pneumatic valves (driven by compressed air), hydraulic valves (driven by liquid pressure such as oil), etc. In addition, there are a combination of the above several driving methods, such as gas-electric valves.
3. Manual valve:
– Manual control of valve action by hand wheel, handle, lever, sprocket, etc. When the opening and closing torque of the valve is large, the wheel or worm gear reducer can be set between the hand wheel and the valve stem. If necessary, it can also use the universal joint and the drive shaft for remote operation.
Fifth, according to the nominal path classification
1. Small diameter valve:
– Valves with nominal diameter DN≤40mm.
2. Medium diameter valve:
– Valves with nominal diameter DN of 50 ~ 300mm.
3. Big diameter valve:
– Valves with nominal diameter DN of 350 ~ 1200mm.
4. Large diameter valve:
– Valves with nominal diameter DN≥1400mm.
Sixth, classification according to structural characteristics
1. Cut-off valve:
– The opening and closing member (valve disc) is driven by the valve stem along the center line of the seat for lifting movement.
2. Plug valve:
– The opening and closing member (cone plug or ball) rotates around its own center line.
3. Swing valve:
– The opening and closing member (valve disc) rotates around the shaft outside the seat.
4. Slide valve:
– The opening and closing pieces slide in a direction perpendicular to the channel.
In summary, there are various classification methods of valves, and each classification method has its specific application scenarios and selection criteria. In practical applications, the appropriate valve type should be selected according to the specific needs.
