Gasket must have proper strength (tensile and crushing) to
resist being torn apart blown out of the joint. Blowout
resistance of a given gasket material is measured by
clamping a test gasket between a pair of flanges and then
subjecting it to higher pressure and temperature. Typically
gasket and flange assembly is heated to certain level of
temperature then the contained pressure is increased until
blowout occurs. Every material is found to withstand a
certain level of service temperature and pressure. After
several such tests, a (P x T) rating is assigned to the
gasket.