Appendix E: Valve Glossary

There are a variety of terms used in the valve industry and the purpose of this appendix is to assist the reader. This valve glossary is a list of definitions, describing the types of valves, their functions, individual components, their materials of construction, and their design characteristics.

A-B

Accessory

A device attached to the actuator which provides an additional function, for example manual operation, positioner, etc.

Actual pressure drop

The difference between the inlet pressure and the outlet pressure of a valve.

Actuator

A device used to open/close or control the valve. Key types include electrical, hydraulic, and pneumatic. Movement may be quarter-turn or multi-turn. Actuators may be used when

• valves are remotely located (e.g., on pipelines)

• valves are located in hazardous areas

• manual operation would be time-consuming (e.g., with larger valves)

Actuator stem

A rod used in linear designed valves connecting the actuator with the stem of the valve.

Actuator stem force

The amount of force that is required to move the actuator stem to either open or close the valve.

Air filter

An accessory added to an actuator to prevent oil, dirt, or water in the air supply from entering the pneumatic actuator.

Air valve

Valve that is used to control the flow of air. Flows are normally small, so solenoid valves are suited.

Angle valve

A valve body where the inlet and outlet ports are at 90 to each other.

Arithmetic average roughness height

The measurement of the smoothness of a surface. In...