Inlet gauge pressure at which a pressure-relief device is set to open under service conditions.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Gauge pressure at the device inlet at which the relief device is set to start opening under service conditions.
Source: API STD 2000, Venting Atmospheric and Low-pressure Storage Tanks, Sixth Edition, November 2009. GlobalStandards