ASP Associate Safety Professional Practice Exam

Pounds per square inch gage (Psig) and pounds per square inch absolute (PSIA) are two different measurements of pressure that are often used in various fields such as engineering, manufacturing, and safety. The relationship between them is crucial to understand when dealing with pressure measurements.

Psig measures pressure relative to atmospheric pressure, meaning it indicates how much pressure is above atmospheric pressure. On the other hand, PSIA measures the total pressure, including atmospheric pressure, so it reflects the pressure relative to a vacuum.

To convert between the two measurements, one must remember that standard atmospheric pressure is approximately 14.7 psi at sea level. Therefore, to obtain PSIA from Psig, you need to add this atmospheric pressure to the Psig value, which yields the total absolute pressure.

By stating that Psig is equal to PSIA minus one standard atmosphere, we acknowledge that PSIA accounts for the atmospheric pressure in addition to the gauge pressure. This relationship is fundamental in fields where pressure calculations are critical, as it allows for accurate measurement and assessment of systems operating under various pressure conditions. Understanding this difference ensures proper safety measures and operational integrity in equipment that relies on pressure measurements.