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.
In fluid processing applications, gasket blowouts are classed as worst-case scenario events. One moment everything is working flawlessly. Pumps are running and pressurized fluids are safely contained. A catastrophic second later, an entire flange pairing or pipe fitting has failed. Without any discernible warning whatsoever, the steam or chemical or fuel load is whistling out of the line as a highly energetic spout. A site disaster could be seconds away.
Assessing the Pressure-Fuelled Consequences
A steam leak, one that’s taken place on a pressurized line, can be so concentrated that it forms an invisible spout. If someone were to come in contact with that jet-like stream, the steam would cut through their skin like a cauterizing scalpel. As bad as this scenario is, it can become worse. A pressurized fuel leak will combust if a spark occurs nearby. With chemical leaks, this high-powered puncture will spread near and far while it poisons everything and everyone. And remember, this type of system breach occurs in seconds. There’s no time to come up with a leak prevention plan when high-pressure seals fail catastrophically. Knowing the disastrous potential, there’s a whole field of science dedicated to gasket blowout prevention.
Introducing the Blowout Prevention Factors
When designing high-pressure system gaskets, a series of pressure regulating parameters are addressed. There’s the fastening framework, which creates invisible beams of clamping force. Those beams also penetrate the seal to draw the opposing flange in tight. Tightened in a pattern, all potential axial and radial forces stay counterbalanced. Next, stopping leakage pathways from forming, ones that’ll make themselves known with explosive intensity, flange gasket materials exhibit great mechanical resilience. Obdurate as steel, the inwardly pressed sealing substance also provides a measure of outward pressing energy. It’s this compressibility, plus the material’s innate elasticity, that works in conjunction with the fasteners’ clamping force to create a reliable seal.
Statistically gathered and analysed, these factors are plugged into engineering equations and gasket blowout simulations. The different seals are tested to destruction within virtual computer spaces. Even then, the job’s not done. The next stage involves placing the seals within controlled test scenarios, where they’re then exposed to substantial amounts of mechanical stress. Again and again, blowout science procedures test different gasket families to destruction. Above and beyond such design precautions, there are yet more measures. One redundant safety system layer is layered upon the next. In all likelihood, those measures will never be used. All the same, they exist, and they’re continually maintained to ensure proper operation, should that worst case scenario ever happen. Finally, Blowout Prevention (BOP) valves are installed to offload those catastrophic pressures.