Valve is a device used to control the direction, pressure and flow of fluid in the fluid system. It can make the medium (liquid, gas, powder) in piping and equipment flow or stop and control its flow.

Valve is the control part of pipeline fluid delivery system. It is used to change the channel section and the direction of medium flow. It has the functions of diversion, cut-off, throttling, check, diversion or overflow pressure relief. Valves for fluid control range from the simplest cut-off valves to various valves used in extremely complex automatic control systems. The nominal diameter of valves ranges from very small instrument valves to industrial pipeline valves with a diameter of 10 m. It can be used to control the flow of water, steam, oil, gas, mud, corrosive media, liquid metal and radioactive fluids. The working pressure of the valve can be from 0.0013 MPa to 1000 MPa, and the working temperature can be from - 270 C to 1430 C.

Valve control can adopt a variety of transmission modes, such as manual, electric, hydraulic, pneumatic, turbine, electromagnetic, electro-hydraulic, electro-hydraulic, pneumatic, spur gear, bevel gear drive, etc. Under the action of pressure, temperature or other forms of sensing signals, the valve can operate according to the predetermined requirements or independent of sensing signals. For simple opening or closing, the valve relies on driving or automatic mechanism to make the opening and closing parts move up and down, slip, swing or turn, thus changing the size of its runner area to achieve its control function.

Cleaning steps

Valve components must undergo the following processes before assembly:

1. According to the processing requirements, some parts need to be polished, and there can be no burrs on the surface.

2. Degreasing of all parts and components;

3. After degreasing, pickling and passivation are carried out, and the detergent does not contain phosphorus.

4. Rinse with pure water after pickling and purification, and there can be no residue of chemicals. This step is omitted for carbon steel parts.

5. Dry the parts one by one with non-woven fabrics. Do not keep the surface of the parts such as wired wool, or use clean nitrogen to dry them.

6. Use non-woven cloth or precision filter paper to analyze pure alcohol to wipe each part until there is no dirty color.

Assembly requirements

Clean parts must be sealed for installation. The requirements for the installation process are as follows:

1. Installation workshop must ensure cleanliness, or build temporary clean areas, such as using newly purchased coloured strip cloth or plastic film, to prevent dust from entering during installation.

2. The assembly workers must wear clean cotton overalls, cotton caps on their heads, no hair leakage, clean shoes on their feet, plastic gloves on their hands and degreasing.

3. Tools for assembly must be degreased and cleaned before assembly to ensure cleanliness.