ISA Certified Control Systems Technician (CCST) program
Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.
In the plot of inherent control valve characteristics shown below, what characteristic does curve C represent?
A. Equal percentage
B. Leak tight shutoff
D. Quick opening
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.
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.
References: Hans D. Baumann; Control Valve Primer: A User's Guide, Fourth Edition, ISA Press, 2009.