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AutoQuiz: What Is the Purpose of a Valve Positioner?

The post AutoQuiz: What Is the Purpose of a Valve Positioner? first appeared on the ISA Interchange blog site.

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.

A valve positioner is usually recommended as an accessory to a control valve for which situation described below?

a) for control valves with bodies over 2 inches (5 cm) in order to overcome actuator spring forces
b) for control valves that are constructed of carbon steel or bronze
c) for control valves that are experiencing a large degree of hysteresis
d) for split-body control valves
e) none of the above

Click Here to Reveal the Answer

Answer A is not correct. The use of positioners is not dependent upon valve size.
Answer B is not correct. Use of a valve positioner is not related to the materials of construction of a valve.
Answer D is not correct. Use of a valve positioner is not related to the valve body type.

The correct answer is C. A positioner adjusts the pneumatic output to a valve actuator so that the requested position of the valve from a controller is achieved. A valve positioner can correct for any valve inaccuracies with regard to the controller demand signal versus the actual valve stem position, regardless of the amount of valve travel change or direction of valve travel.

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, 2nd Edition

About the Editor
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master’s degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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Source: ISA News