Print this article

Comment

1 September 2002

Test your knowledge with CCST . . .

The following sample questions (not actual exam questions) appear in the Certified Control System Technician (CCST) study guide published by ISA.

CCST questions

The content area for these questions is Domain 3—troubleshooting.

1) One of the most important considerations of the installation of an electromagnetic flowmeter is:

A. the Reynolds Number of the fluid

B. the use of a straightening vane

C. bonding the flowmeter to the piping

D. observing the correct polarity

2) Control valves that have a plug positioned by a stem, which slides through a packing gland, are often referred to as _____.

A. rotary motion control valves

B. linear stem motion control valves

C. ball control valves

D. motorized control valves

3) Butterfly valves are _____.

A. rotary motion control valves

B. linear stem motion control valves

C. ball control valves

D. motorized control valves

CCST answers

1) The answer is C. The principle behind magnetic flowmeters is Faraday's Law. When a conductor (the fluid in the pipe) moves at right angles to a magnetic field, a voltage difference is induced in the conductor that is proportional to the conductor's velocity. Bonding is the electrical connection of the piping system, which includes the flowmeter electronics, to keep them at their designed potential. If proper bonding does not happen, stray voltage in the fluid can affect and alter the measurement by causing a current to take an incorrect path to ground or elsewhere. Bonding helps prevent this.

Wafer-style flowmeters establish a magnetic field across the entire cross-section of a pipe from outside the pipe. This design allows the magnetic field to be evenly exposed to flow conditions at all points in the pipe cross section.

Insertion-style flowmeters, use sensors inserted into the pipe to generate the magnetic field. Electrodes in the sensors detect the voltage across the liquid which is used to determine the flowrate.

2) The correct answer is B.

3) The correct answer is A.

—Nicholas Sheble at nsheble@isa.org