Gas Fitter Practice Test

A pressure reading of 14.7 psia is equivalent to:

1. 0 psig

2. 2.31 in W.C.

3. 24.7 psig

4. 27.78 in W.C.

The correct answer is: 0 psig

A pressure reading of 14.7 psia represents atmospheric pressure at sea level, where psia stands for pounds per square inch absolute. In the context of pressure measurement, "psig" (pounds per square inch gauge) measures pressure relative to atmospheric pressure. Since psig is a gauge measurement, it reads zero at atmospheric pressure. Therefore, if the absolute pressure is 14.7 psia, this equates to 0 psig, as there is no additional pressure above atmospheric. This relationship illustrates that the gauge pressure is zero when measured at atmosphere, making it vital for understanding how absolute and gauge pressures relate to each other. In practical terms, whenever a system shows a reading of 14.7 psia, it signifies that there is neither additional pressure nor vacuum present above the standard atmospheric conditions.