Q. Show Gasket Compression?
Gasket compression can also be used as a guide for limiting bolt torque.
Spiral wound gaskets should be compressed to an average of 75% of original thickness to assure adequate seating and prevent over ¬compression. For a 0.175 in (4.5 mm) thickness, this would give a compressed height of 0.130 in +/- 0.005 in (3.3 mm +/- 0.127 mm). Feeler gauges could then be used to check for uniform compression around the flange.
Centering ring thickness is 0.125 in (3.175 mm). Therefore if bolts are torqued so that flange faces just touch centering ring around its periphery, gasket is properly compressed.
Total clear space between centering ring and flange faces should not exceed 0.01 in (0.25 mm).