In all piping systems the flanges, valves and the piping itself have a pressure - temperature relationship. This PxT factor is the result of multiplying the operating pressure times the operating temperature to arrive at a numerical value. This value is not constant and is different at each temperature and pressure combination.
In the table below the PxT factors for carbon steel piping per ANSI B16.34 and saturated steam are shown. The fact that PxT values exists for piping should indicate that such values also exist for gasketing, and just like piping, those values change with differences in the pressure and temperature.