Valve Basic

A valve is a control device for a fluid line. Its basic function is to connect or cut off the circulation of the pipeline ring, change the flow direction of the medium, adjust the pressure and flow of the medium, and protect the normal operation of the pipeline and equipment.

一．Classification of valves

According to the use and function can be divided into:

1. Shut-off valve: cut off or connect the pipeline medium. Such as: gate valve, globe valve, ball valve, butterfly valve, diaphragm valve, plug valve.

2. Check valve: prevent the medium in the pipeline from flowing backward.

3. Distribution valve: change the flow direction of the medium, distribute, separate or mix the medium. Such as distribution valves, steam traps, and three-way ball valves.

4. Regulating valve: adjust the pressure and flow of the medium. Such as pressure reducing valve, regulating valve, throttle valve.

5. Safety valve: prevent the medium pressure in the device from exceeding the specified value, and provide overpressure safety protection.

二. Basic parameters of the valve

1. The nominal diameter of the valve (DN).

2. The nominal pressure of the valve (PN).

3. Pressure and temperature rating of the valve: When the working temperature of the valve exceeds the reference temperature of the nominal pressure, its maximum working pressure must be reduced accordingly.

4. Valve pressure unit conversion:

5. The applicable medium of the valve:

Industrial valves are used in petroleum, chemical industry, metallurgy, electric power, nuclear energy and other industries. The media passed through include gases (air, steam, ammonia, coal gas, petroleum gas, natural gas, etc.); liquids (water, liquid ammonia, oil, acids, alkalis, etc.). Some of them are as corrosive as machine guns, and others are highly radioactive.