November/December 2011

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.

CCST question

A flow metering device comprised of a body, flow straightener, hub, bearing, rotor, and pickup is called a:

A.  Vortex shedding flowmeter

B.  Magnetic flowmeter

C.  Parshall flume

D.  Turbine flowmeter

Answer (A) is not correct, since a major component of a vortex shedding flowmeter is a bluff body, and vortex flowmeters do not have hubs, bearings, or rotors.

Answer (B) is not correct, since a major component of a magnetic flowmeter is an iron core, and these flowmeters do not have hubs, bearings, or rotors.

Answer (C) is not correct, since Parshall flumes do not have any moving parts and require a measurement of fluid level above the convergence section and above the throat section.

The correct answer is (D).  The problem statement describes the major parts of a turbine flowmeter. The rotor is supported by the hubs and bearings inside of a flowmeter body, and as the rotor spins, the number of revolutions is determined with a magnetic pickup.  The rotational speed of the rotor and the frequency of pulses are proportional to the volumetric flow rate through the meter.

Reference: Spitzer, David W., Flow Measurement, 2nd Edition