A valve is a pipeline accessory. It is a device used to change the cross section of a pipeline and the direction of medium flow, and to control the pressure, flow, and temperature of the conveying medium. Specifically, it has the following purposes:
1. Connect or cut off the medium in each section of the pipeline, such as: gate valve, globe valve, butterfly valve, ball valve, cock, etc.
2. Adjust the flow and pressure of the pipeline, such as: regulating valve, throttle valve, pressure reducing valve, butterfly valve, ball valve, etc.
3. Change the medium flow direction, such as: distribution valve, three-way cock, three-way ball valve, etc.
4. Used for overpressure protection, such as: safety valve, overflow valve.
5. Prevent backflow of medium in the pipeline, such as: check valve
6. Indicate and adjust the liquid level, such as: liquid level indicator, liquid level regulator, etc.
7. Separation of gas and water in the pipeline, such as steam trap and air trap.
8. Temperature regulation in the pipeline, such as: temperature regulating valve, temperature and pressure reducing device.
The classification of valves is mainly divided according to the purpose and structural characteristics. But in general, we use the general classification method, which is divided according to principle, function and structure. This method is the most common classification method at home and abroad. Here, according to the material of the valve body, the valve can be divided into:
(1) Metal material valve: its valve body and other parts are made of metal material. Such as cast iron valves, carbon steel valves, alloy steel valves, copper alloy valves, aluminum alloy valves, lead alloy valves, titanium alloy valves, Monel alloy valves, etc.
(2) Non-metallic valve: its valve body and other parts are made of non-metallic material. Such as plastic valves, pottery valves, boring valves, fiberglass valves, etc.
(3) Metal valve body lined valve: The valve body is made of metal, and all the main surfaces in contact with the medium inside are lined, such as rubber lined valves, plastic lined valves, ceramic lined valves, etc.
The main body materials are: C carbon steel, I 1Cr5Mo chromium molybdenum steel, H Cr13 series stainless steel, K malleable cast iron, L aluminum alloy, P 0Cr18Ni9 series stainless steel, PL 00Cr19Ni10 series stainless steel, Q ductile iron, R 0Cr12Ni12Mo2 series stainless steel, RL 00Cr17Ni14Mo2 series Stainless steel, S plastic, T copper and copper alloy, Ti titanium and titanium alloy, V chrome molybdenum vanadium steel, Z gray cast iron.