Valve Definition

A valve is a control device for fluid pipelines. Its basic function is to connect or cut off the flow of medium in the pipeline, change the direction of the medium's flow, regulate the pressure and flow of the medium, and protect the normal operation of pipeline equipment. Valves are usually composed of valve body, valve cover, valve seat, actuating element (valve disc, gate, butterfly plate, diaphragm, etc.), driving mechanism (valve stem and the driving device that moves it), sealing element (packing, gasket, etc.) and fastening parts, etc.

Valve Classification

Valves have a wide range of uses and numerous types, and there are also many classification methods.

1.1 By driving method

Automatic valves: Valves that operate by the ability of the medium (liquid, gas, etc.) itself. Such as check valves, safety valves, regulating valves, steam traps, pressure reducing valves, etc.

Drive valves: Valves that are operated by manual, electric, hydraulic, or pneumatic means. Such as gate valves, globe valves, butterfly valves, ball valves, plug valves, etc.

(1) Manual valves: Valves that are operated by handwheel, handle, lever or chain wheel, etc., by human power. When a large torque needs to be transmitted, a worm gear, gear, etc. can be used as a speed reduction device.

(2) Electric valves: Valves that are operated by an electric motor, electromagnet or other electrical device.

(3) Hydraulic: Driven by (water, oil).

(4) Pneumatic: Driven by compressed air.

1.2 By pressure

Low pressure: Valves with nominal pressure less than 1.6 MPa.

Medium pressure valves: Valves with nominal pressure ranging from 2.5 to 6.4 MPa.

High pressure valves: Valves with nominal pressure ranging from 10 to 80 MPa.

Ultra-high pressure valves: Valves with nominal pressure greater than 100 MPa.

1.3 By temperature

High temperature valves: Valves with temperature greater than 450℃.

Medium temperature valves: Valves with temperature ranging from 120℃ to 450℃.

Normal temperature valves: Valves with temperature ranging from -29℃ to 120℃.

Low temperature valves: Valves with temperature ranging from -100℃ to -29℃.

Ultra-low temperature valves: Valves with temperature less than -100℃.

1.4 By nominal size classification

Small-diameter valves: Valves with nominal size of DN ≤ 40mm.

Medium-diameter valves: Valves with nominal size ranging from DN 50 to 300mm.

Large-diameter valves: Valves with nominal size ranging from DN 350 to 1200mm.

Extra-large-diameter valves: Valves with nominal size of DN ≥ 1400mm.

1.5 By installation method with pipelines

Flange connection valves: Valves with a flange on the valve body, connected to the pipeline by flange.

Threaded connection valves: Valves with internal or external threads on the valve body, connected to the pipeline by thread.

Welding connection valves: Valves with weld seams on the valve body, connected to the pipeline by welding.

Clamping connection valves: Valves with clamping holes on the valve body, connected to the pipeline by clamping.

Socket connection valves: Valves connected by socket.

1.6 By purpose

Cut-off valves: Mainly used to connect or cut off the medium in the pipeline, such as gate valves, globe valves, ball valves, butterfly valves, etc.

Check valves: Used to prevent the reverse flow of the medium, such as check valves.

Regulating valves: Mainly used to regulate the pressure and flow of the medium in the pipeline, such as flow regulating valves, regulating valves, pressure reducing valves.

Diversion valves: Used to change the flow direction of the medium in the pipeline, serving the purpose of distributing and diverting the medium, such as three-way valves, distribution valves, slide valves, etc.

Safety valves: Used to discharge excess medium when the medium pressure exceeds the specified value, ensuring the safety of the pipeline system and equipment, such as safety valves, emergency valves. Other special dedicated valves: such as steam trap valves, vent valves, and discharge valves, etc.