What is a valve?

A valve is a type of piping accessory used to change the flow path and direction of the medium, controlling the flow of the transported substance. Specifically, valves serve several purposes:

1. Opening or closing the flow of the medium in a pipeline – such as gate valves, globe valves, ball valves, plug valves, diaphragm valves, and butterfly valves.
2. Regulating and controlling the flow rate and pressure of the medium in a pipeline – such as throttling valves, control valves, pressure relief valves, and safety valves.
3. Changing the direction of flow – such as diverter valves, three-way plug valves, and three-way or four-way ball valves.
4. Preventing backflow in the pipeline – including various types of check valves, foot valves, etc.
5. Separation of media – such as steam trap valves, air trap valves, and others.
6. Indicating and controlling the liquid level – including liquid level indicators and level controllers.
7. Other specialized applications – such as temperature control valves and emergency shutoff valves for overcurrent protection.

Among all types of general-purpose valves, those used for opening and closing the flow of medium in a pipeline make up approximately 80% of the total number of valves.