ANSI/ISA TR75.25.02-2000 (R2010)

This technical report applies to throttling control valves in closed loop control applications. The concepthas some application to open loop control applications. It does not address control valves used in on-offcontrol service. The control valve in the context of this document includes the following components:Valve: A valve is a device used for the control of fluid flow. It consists of a fluid containing valve bodyassembly, one or more ports between connection openings and a moveable closure member, whichopens, restricts or closes the port(s) (see ANSI/ISA-75.05.01-2000, Control Valve Terminology).Actuator: An actuator is a device that supplies the force and causes the movement of the valve closuremember. Commonly these are fluid or electrically powered (see ANSI/ISA-75.05.01-2000). Actuators oftenuse air but other types use electric, hydraulic and electro-hydraulic power.Motion conversion mechanism: A mechanism installed between the valve and the power unit of theactuator to convert between linear and rotary motion where required. The conversion may be from linearactuator action to rotary valve operation or from rotary actuator action to linear valve operation.Accessories: Additional devices used in the operation of the control valve. As described inANSI/ISA-75.05.01-2000, typical examples include a positioner, transducer, signal booster relay, air set,snubber, etc.