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1 August 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 1—calibration.

1) If a cubic foot of water weighs 62.4 pounds, it exerts a pressure of how many pounds per square inch (psi)?

A. 0.036

B. 2.308

C. 0.433

D. 14.7

2) Head is another way of expressing:

A. gallons

B. pressure

C. length

D. mass

3) Approximately what is the pressure, in psi, at the bottom of a 20-foot tank filled with a fluid that has a specific gravity of 1.5?

A. 8.7

B. 12.99

C. 5

D. 35

CCST answers

1) Imagine a cubic foot of water. It's 12 inches wide, 12 inches back, and 12 inches high. Because the base of this cube of water is 12 by 12, we know that the base is 144 square inches. The question asks how many pounds per square inch does the box exert. Put 62.4 pounds in the numerator and 144 square inches in the denominator, divide, and you get 0.433 psi—answer C.

2) The correct answer is B.

3) Specific gravity (SG) is the density (mass/volume) of a substance with reference to the density of water. Thus, the SG of water is 1.0. A substance, which has an SG of 1.5, as in this problem, has 1.5 times the mass of water. So if we take the calcula tion from question No. 1 above, which asked for the psi of a 1-foot-high column of water, and multiply it by 20, we get the psi of the 20-foot-high column for this problem. Now we multiply that by 1.5 because the substance in this problem has 1.5 times the mass of water (0.433 x 20 x 1.5 = 12.99), and we get the answer, B.