1. Definition of valves:
"Valve" is defined as the device used to control the direction, pressure and flow of fluid in the fluid system. The valve is a device that makes the medium (liquid, gas, powder) in the piping and equipment flow or stop, and can control its flow.
2. According to the different functions of the opening and closing valves, there are many kinds of valve classification methods. Here are the following.
1. Classification by function and purpose
(1) Block valve: block valve also known as closed-circuit valve, its role is to connect or block the medium in the pipeline. Block valves include gate valve, globe valve, plug valve, ball valve, butterfly valve and diaphragm.
(2) Check valve: check valve is also known as one-way valve or check valve. Its function is to prevent backflow of medium in the pipeline. The bottom valve of water pump is also a check valve.
(3) Safety valve: the function of safety valve 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: regulating valve includes regulating valve, throttle valve and pressure reducing valve, whose function is to regulate the pressure, flow and other parameters of medium.
(5) Diverter valve: diverter valves include various distribution valves and drain valves, whose function is to distribute, separate or mix the medium in the pipeline.
2. Classification by nominal pressure
(1) Vacuum valve: refers to the valve whose working pressure is lower than the standard atmospheric pressure.
(2) Low pressure valve: refers to the valve with nominal pressure PN ≤ 1.6Mpa.
(3) Medium pressure valve: refers to the valve with nominal pressure PN of 2.5, 4.0 and 6.4Mpa.
(4) High pressure valve: refers to the valve with a pressure PN of 10-80mpa.
(5) Ultra high pressure valve: refers to the valve with nominal pressure PN ≥ 100MPa.
3. Classification by operating temperature
(1) Ultra low temperature valve: used for the valve with medium working temperature T < - 100 ℃.
(2) Low temperature valve: it is used for the valve with medium working temperature - 100 ℃ ≤ t ≤ - 40 ℃.
(3) Normal temperature valve: used for the valve with medium working temperature - 40 ℃ ≤ t ≤ 120 ℃.
(4) Medium temperature valve: for medium operating temperature 120 ℃
(5) High temperature valve: used for the valve with medium working temperature T > 450 ℃.
4. Classification by driving mode
(1) Automatic valve refers to the valve that does not need external force to drive, but relies on the energy of the medium itself to make the valve act. Such as safety valve, pressure reducing valve, drain valve, check valve, automatic control valve, etc.
(2) Power driven valve: power driven valve can be driven by various power sources.
Electric valve: valve driven by electricity.
Pneumatic valve: valve driven by compressed air.
Hydraulic valve: valve driven by liquid pressure such as oil.
In addition, there are several combinations of the above driving modes, such as gas electric valve, etc.
(3) Hand valve: hand wheel, handle, lever and sprocket are used to operate the hand valve. When the opening and closing torque of the valve is large, this wheel or worm gear reducer can be set between the hand wheel and the valve rod. If necessary, the universal joint and transmission shaft can also be used for remote operation.
5. Classification by nominal diameter
(1) Small diameter valve: valve with nominal diameter DN ≤ 40mm.
(2) Medium diameter valve: valve with nominal diameter DN of 50-300 mm.
(3) Large diameter valve: valve with nominal valve DN of 350-1200mm.
(4) Oversize valve: valve with nominal diameter DN ≥ 1400mm.
6. Classification by structural features
(1) Shut off valve: the opening and closing parts (disc) are driven by the valve stem to move up and down along the center line of the valve seat;
(2) Plug valve: the opening and closing parts (gate valves) are driven by the valve stem to move up and down along the center line perpendicular to the valve seat;
(3) Plug valve: the opening and closing parts (cone plug or ball) rotate around their own center line;
(4) Swing valve: the gate (disc) rotates around the shaft outside the seat;
(5) Butterfly valve: the gate (disc) rotates around the fixed shaft in the valve seat;
(6) Slide valve: the gate slides perpendicular to the channel.
7. Classification by connection method
(1) Threaded valve: the valve body has internal or external thread, which is connected with pipeline thread.
(2) Flange connected valve: the valve body is equipped with flange, which is connected with the pipeline flange.
(3) Welding connection valve: the valve body is provided with welding groove, which is welded to the pipeline.
(4) Clamp connection valve: the valve body is provided with a clamp, which is connected with the pipe clamp.
(5) Ferrule connecting valve: ferrule connecting with pipeline.
(6) Clamp connection valve: the connection form that the valve and two end pipes are directly clamped together by bolts.
8. Classification by valve body material
(1) Metal material valve: the valve body and other parts are made of metal materials. Such as cast iron valve, carbon steel valve, alloy steel valve, copper alloy valve, aluminum alloy valve, lead alloy valve, titanium alloy valve, Monel alloy valve, etc.
(2) Non metallic material valve: the valve body and other parts are made of non-metallic materials. Such as plastic valve, ceramic valve, enamel valve, FRP valve, etc.
(3) Metal body lined valve: the valve body is metal in shape, and the main surfaces in contact with the medium are lined, such as rubber lined valve, plastic lined valve, ceramic lined valve, etc.
9. Valve model arrangement
The valve model shall generally indicate the valve type, driving mode, connection form, structural characteristics, sealing surface material, valve body material, nominal pressure and other elements. The standardization of valve models provides convenience for the design, selection and sale of valves. Nowadays, there are more and more types and materials of valves, and the type designation of valves is more and more complicated. Although there is a unified standard for valve type designation in China, it is increasingly unable to meet the needs of valve industry development. At present, valve manufacturers generally adopt the unified numbering method; where the unified numbering method cannot be adopted, each manufacturer shall formulate the numbering method according to their own needs.