Dealing with Expansion and Contraction of Flange Gaskets

17 June 2019

Malleable metals and compressible elastomers are superior gasketing materials. They form powerful seals when extreme flanging forces are applied. However, that principal feature can sometimes go awry. It backfires on an application. Instead of demonstrating a talent for countering flange load, unchecked contraction and/or expansion energies interfere with a gasket’s operational functions.

Determining Ring Distorting Causes

Temperature extremes cause materials to expand or contract. If a great deal of thermal energy finds its way into a gasket’s material, that sealing substance will expand. At the other end of the temperature scale, the opposite issue takes hold. The icy fluid passing through the flanges chills the gasket, the material contracts, and a tiny void grows under the flange faces. Through that void, a leakage pathway could form. Likewise, in a heat-expanding seal, the perfectly aligned ring could shift until the gasket isn’t seated properly anymore. Worst-case scenario, a frozen and materially contracted gasket will crack because its once resilient structure becomes inelastic. Tortured by heat, the sealing material distorts and loses structural integrity. What a disconcerting, seal weakening state of affairs. Not to worry, there’s more than one way to handle this predicament.

Dealing With Gasket Deforming Energies

Straight to the point, don’t select a gasket elastomer or fibre that’s not designed to handle large temperature extremes. If, for example, the fluid stream contains pressurized steam or hot oil, select a ring that’s made of graphite. Formed into a foil jacket or a series of laminated rings, composite graphite gaskets are designed to handle high-temperature swings. Ceramic fibres and fluorosilicone seals are also designed to hold firm when high-temperature loads strike. Spiral-wound metal/ceramic fillers are another possibility, with low creep alloys delivering superior stability. Due to their expansion and contraction-neutral characteristics, alloy seals exhibit low distortion coefficients.

Located indoors or below ground, pipes aren’t exposed to UV (ultraviolet rays) or radiated heat. If a pipeline does run above ground, paint or a special coating will block the damaging rays. Better yet, in addition to a gasket material’s temperature resisting properties, that material should exhibit a satisfactorily high UV resistance feature. Take note, some chemical reagents can also impact sealing material integrity. In response to this possibility, select gaskets that are immune to chemical assault. By the way, environmental extremes can strike other parts of a pipeline. As the outside temperature soaks into a pipe, it conducts thermally along and through the rolled metal until it reaches the flange faces. If the externally generated heat, or cold, isn’t to overcome the flange clamping force, then a properly administered bolt jointing pattern must be followed.

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