Bolted flange gasket technology continually evolves with new designs and materials that provide more reliable and durable seals. Due to advances in gasket technology, engineers, operators and maintenance personnel can choose from a large selection of gasket styles and types. Therefore, obviously one of the first steps to consider in properly installing any gasket is its compatibility to the application and service it is being placed in to. Another very important step in any proper installation of a gasket is applying the right amount of bolt load.
Use The Right Amount of Bolt Load
Proper installation primarily involves the method of tightening the bolts. After all, a bolted flange gasket is a mechanical system fundamentally based on the spring-like force exerted by the stretched fasteners and the other compressed joint components. Sufficient torque must be applied to create the compressive load that causes the gasket to consolidate and flow in to and fill any irregularities in the sealed mating surfaces. The bolt load also causes serrations of the flange seating surface to bite the gasket, mitigating lateral gasket movement and blowout. The higher the compressive load, both initially and during service, the higher the blowout (gross leakage) resistance. However, if too much torque is applied, the seal will be compromised (crushed) and destroyed.
Use The Right Bolting Pattern (as Recommended in an engineering paper entitled Proper Installation of a Bolted Joint Gasket)
- Tighten the bolts to compress the gasket uniformly, utilizing a star bolting pattern (see Figure 1). After initially bringing all bolts to snug or finger-tight, all bolts should be tightened in one-third increments at each pass. The sequence in which bolts or studs are tightened has a substantial effect on the distribution of the assembly pressure (compression) on the gasket. Improper bolting may move the fl ange out of parallel. A gasket will usually be able to compensate for a small amount of distortion of this type, but serious difficulties may emerge if the flanges are substantially out of parallel.
- Make a final check pass at the target torque value moving consecutively from bolt to bolt.
- Re-torque 12 to 24 hours after initial installation, whenever possible.
- Observe all safety standards including lockout/tag out procedures.
- Never use liquid or metallic based anti-stick or lubricating compounds on the gaskets. Premature failure could result.
For more information about the selecting the right type of gasket for your application special shape or size gaskets, metal gaskets o-rings, pump and valve packing or rubber products contact Four States Gasket and Rubber, Inc.
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