This technical report applies to throttling control valves inclosed loop control applications. The concept has some applicationto open loop control applications. It does not address controlvalves used in on-off control service. The “control valve” in thecontext of this document includes the following components:
Valve: A valve is a device used for the controlof fluid flow. It consists of a fluid containing valve bodyassembly, one or more ports between connection openings and amoveable closure member, which opens, restricts or closes theport(s) (see ANSI/ISA-75.05.01-2000, “Control ValveTerminology”).
Actuator: An actuator is a device that suppliesthe force and causes the movement of the valve closure member.Commonly these are fluid or electrically powered (seeANSI/ISA-75.05.01-2000). Actuators often use air but other typesuse electric, hydraulic and electro-hydraulic power.
Motion conversion mechanism: A mechanisminstalled between the valve and the power unit of the actuator toconvert between linear and rotary motion where required. Theconversion may be from linear actuator action to rotary valveoperation or from rotary actuator action to linear valveoperation.
Accessories: Additional devices used in theoperation 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.
Purpose
This technical report describes the characteristic response of acontrol valve to step input signal changes. It considers thefactors that affect this response, the impact of the response onthe quality of process control, and the appropriate control valvespecifications. In this document, a control valve is the completecontrol valve body, with actuator and any accessories required fornormal operation assembled and ready for use. This documentsupports standard ANSI/ISA-75.25.01-2000 “Test Procedure forControl Valve Response Measurement from Step Inputs”. See thestandard for the test procedures.
Users and manufacturers have developed a better understanding ofthe effects of control valve response characteristics on processcontrol. This document identifies and defines four regions ofcontrol valve response to step input changes of varying sizes.Existing standards do not include the definitions and methods tomeasure certain valve characteristics now understood to beimportant. This technical report provides guidance that can be usedto relate the control valve performance to process control.
- Edition:
- 00
- Published:
- 01/01/2000
- ANSI:
- ANSI Approved
- Number of Pages:
- 44
- File Size:
- 1 file , 290 KB
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