Bolting should be of sufficient strength to achieve proper compression of the gasket, to not only seal the joint, but to maintain the seal without exceeding the yield strength of the bolts being used. The torque values in our torque tables are based on using ASTM A193 Grade B7 studs and 2H heavy hex nuts lubricated with never seize.
Since sheet gasket materials have micropores, they must be sufficiently compressed to reduce porosity. Without adequate compression the system pressure can force the contained fluid into the gasket and degrade it.
Therefore, when installing the gasket it is important that good technique be followed including cleaning the flanges, inspecting the flange face and the bolts and bringing the flanges together parallel and in stages. Many field problems arise from improperly installed gaskets. Refer to the section on gasket installation.