A new gas piping system is to be pressure tested at 10 psig. Take as given the rule that the test gauge must be selected so that the test pressure falls between 20 percent and 80 percent of the gauge's full scale range. Which gauge satisfies that rule?
- A 30 psi gauge
- BA 10 psi gauge, matching the test pressure exactly
- CA 100 psi gauge, giving plenty of margin above the test pressure
- DA 200 psi gauge, so that the needle can never be driven off the scale
Where to look it up
Explicit exercise assumptions; not a universal code requirement.
Why A is correct
Apply the supplied 20–80 percent rule. At 10 psi, a 30 psi full-scale gauge reads 10 / 30 = 33.3 percent of full scale and passes. The other choices read 100 percent, 10 percent and 5 percent, respectively, so each fails a stated boundary. Equivalently, acceptable full-scale values run from 10 / 0.80 = 12.5 psi through 10 / 0.20 = 50 psi. This checks only the given range rule; resolution, accuracy, calibration and applicable test requirements must also be checked.