The post What Does It Mean When the Percentage of Flow Through a Valve Equals the Percentage of Plug Movement? first appeared on the ISA Interchange blog site.
Today’s automation industry quiz question showcases ISA’s new course, Control Valve Mechanics and Operations from Analog to Digital.
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When the percentage of flow through a valve equals the percentage of plug movement, a valve has:
A) Linear flow characteristic
B) Equal percentage flow characteristic
C) Quick opening flow characteristic
D) Curved flow characteristic
E) None of the above
The answer is A, linear flow characteristic. If a valve with a linear flow characteristic is open to 20% of its maximum, then the flow through the valve is 20% of its maximum. As to an equal percentage valve, choice B, if it were open 20%, the flow would be less than 20% of its maximum. It might be only 5%, for instance. Choice C, quick opening flow characteristic, would describe a valve that lets a lot of flow go through the valve just as it is opening. At 20% of full open for instance, the flow might already be 60% of its maximum-ergo the name quick opening. Choice D is not a flow characteristic.
Source: ISA News
