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.
In the plot of inherent control valve characteristics shown in the post image, what characteristic does curve C represent?
a) equal percentage
b) leak tight shutoff
d) quick opening
e) none of the above
Click Here to Reveal the Answer
Leak-tight shutoff is not represented on this chart. Curve B represents the linear valve characteristic, where each increment of valve movement provides the same incremental increase in flow. Curve A represents the quick opening valve characteristic, where the flow increases rapidly with valve movement.
The correct answer is A, equal percentage. Curve C represents the equal percentage valve characteristic, where each increment of valve movement provides the same percentage increase in flow.
Reference: Hans D. Baumann, Control Valve Primer: A User’s Guide, Fourth Edition.
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