How is a gasket selection affected by the flange type?
Flanges come in all shapes and sizes, and the type of flange used in a service has a large impact on the type of gasketing material recommended. Standard ANSI raised face flanges are best suited for use with compressed fiber and GYLON® gaskets. Elastomer (rubber) gaskets may be crushed in these flanges.
Flat faced non-metallic flanges seal best with elastomeric (rubber) gaskets, such as the various STRESS SAVER® gasket styles. GYLON® Style 3545 may also be suitable for some applications. Compressed fiber and standard GYLON® are frequently used in flat-faced carbon steel flanges, but the compressive stress available in these flanges is well below our minimums. The result is that the gaskets are compressed very little; if there is a significant flange irregularity present, the gasket may not seal. Since leakage rates of gaskets depend on the available compressive stress, the joint may not be as tight as the customer would like.
Glass-lined flanges are found in many chemical applications. Due to the inherent "waviness" created when these flanges are fired to apply the glass, the softer GYLON® styles such as Styles 3545, 3565, and 3504 are preferred. The gap between the flanges, when placed together empty, must be measured before the gasket is ordered. Gasket thickness should be four to five times the maximum gap observed.
Stainless steel (SS) flanges are common in many plants for chemical service, and often utilize low strength SS bolts. Due to the chemicals present and the low compressive stress generated by the bolts, Styles 3545, 3565, and 3504 are often recommended. We do prefer, however, the use of high strength, strain-hardened stainless steel bolts. Styles 3000, 98206 and Stress Saver XP are the preferred choices in water service in stainless steel flanges, due to their very low leachable chlorides. Consult Garlock Engineering when considering other styles. See Stress Saver XP in the Engineered Gasketing catalog.