Basic Parts:

A valve is a mechanical device which controls the flow of fluid and pressure inside a system or procedure. A valve controls system or procedure fluid flow and pressure through performing any of the subsequent functions:

1. Stopping and starting fluid flow

2. Varying (throttling) the amount of fluid flow

3. Controlling the direction of fluid flow

4. Regulating downstream system or process pressure

5. Relieving component or piping over pressure

There are several valve designs and categories which satisfy one or more of the functions recognized above. A multitude of valve categorized and designs safely accommodate a huge variety of industrial applications.

Regardless of categories, all valves have the subsequent basic elements: the body, trim (internal elements), bonnet, actuator, and packing. A basic element of a valve is described in Figure.