Numerically based literacy is applied when selecting a gasket. An engineer runs a finger down a list, finds the results of the scan pleasing, and the decision is made. Interestingly, gasket parameters are also stored in graphical formats. On graphs, two axial lines cross. A curve intersects. It creates a picture of a seal’s mechanical characteristics. That, in a nutshell, is a technique that also applies to gasket compression curves.

Plotting the Two Key Datasets

This is a performance-illustrating tool. The curve clearly depicts how a specified gasket will react as it’s compressed between two flange faces. It shows material densifications as fastener loads are applied. As Y-axis load factors increase, the X-axis shows how well the seal handles the compressive energies. To measure the densification, the material crushing energies are translated into dimensions. Essentially, as a load bears down, the Y-axis measurements are recorded. Meanwhile, simultaneously recorded on the X-axis, a loss of gasket thickness is measured. At any point where those energies intersect, a mark is made on the graph. As those marks accumulate, a line is plotted through them until the gasket compression curve becomes readily apparent.

Why Is This Curve An Essential Performance Benchmarker?

Engineers create the curves as performance baselines. They show how the material stiffness of a seal reacts as it’s placed under a compressive load. The depth of the arc of the curve, how it flattens or straightens out at different clamping pressures, tells an important story. Admittedly, it takes a trained engineer to create this shape, but that information, once garnered, can be read by an installation professional. At any given point along the axial lines, that trained eye sees how a gasket deforms under pressure. On applying fastener force, on taking that turn energy higher than what’s suggested by the curve, a gasket could extrude out and create a number of leak pathways. Kept within the plotted curve limits, such overloading calamities become unlikely because the installer defers to the gasket’s material stiffness parameters, as described in the seal’s compression curve.

Unlike a static numerical seal parameter, gasket compression curves show a broad range of possible loading effects. As the loads increase or reduce, the installer sees how a gasket handles the different loads. Intended as a material stiffness-to-load factor interpreting guide, the compression curves show how different gaskets densify and compress. More than this, they demonstrate material deformability, extrusion dangers, and potential leakage pathways. Do always comply with a list of numerical behavioural parameters when selecting a gasket. Fortify this approach by knowing how the material will react to a given load.

Gasket leaks can cause problematic fugitive emissions. These escaping gasses or vapours then go on to contribute to a worldwide challenge. They worsen the state of already contentious local air pollution problems. Rising higher, the emissions participate in a globally consequential, environmentally-damaging state of affairs. The planet Earth suffers as its blanketing atmosphere fills with poison. Who knew a faulty gasket could cause such a profoundly disturbing series of world-impacting maladies?

Reducing Fugitive Emissions

Okay, the above passage of text might sound overly dramatic, but there’s more than a seed of truth there. The only additional nugget of perspective-giving context that needs to be added is this: no single industrial complex is responsible for the environmental crisis. At the same time, every emissions-producing facility has to accept some responsibility. To demonstrate acceptance of this truism, eco-conscious plant managers call upon the services of reputable gasket suppliers. By taking this virtuous path, by sticking with a seal vendor who prioritizes emissions neutralizing solutions above all other concerns, site managers side with the environment.

Reputable Gasket Suppliers

Of course, there’s more to this matter than a virtuous attitude. A principled frame of mind helps, but these are business runnings, and they’re looking for profits. Without sounding too pessimistic, it takes more than a non-specific threat to waylay a corporate-sized industrial complex. The idea that acid rains might fall a thousand miles away won’t necessarily keep such an emission-leaking facility in check. That’s why there are laws for such things. Environmental agencies bring “sniffer” tools to company sites, and if those sites are found to be producing fugitive emissions, then that compliance-breaking act is punished. Extracted financially, the only way to prevent a future gasket-weakening violation is to call a reputable gasket supplier.

Weighing The Costs

There’s more to this challenge than first meets the eye. Greenhouse gasses are a clear threat whether the law-violating company believes in them or not. What of the local costs? Escaping gasses can slowly poison local communities. They can accumulate in lower grounds as heavier than air discharges, which then combust. Lastly, there’s the more practical matter, the fact that fugitive emissions represent significant company losses. Like money sifting its way through a substandard seal, the invisible vapours steal a portion of a facilities’ production revenue.

It’s a three-way challenge. Localized environmental damage. Tiny quantities of escaping gas can accumulate. Then there’s the air pollution challenge, which can have far-reaching consequences. Company losses are the third factor of concern. By rule of law, such fugitive emissions are classed as serious violations. A company maintenance program will reduce such transgressions, but only a reputable gasket supplier can properly eliminate the hazard.

In an ideal world, an engineer would select an overly thickened gasket. Then the flange bolts would tighten until even the slightest leak pathway was filled by the incredibly compressed material. That’s not a real-world option, not when there are physical constraints to evaluate. For starters, all of that flange pressure, as applied by the ring of bolts, would create great stress along the flange faces.

A Deterministic View Of Flange Stressors

Again, thicker gaskets do a better job of filling flange face irregularities, so shouldn’t this thicker-than-average seal be used as the preferred solution to any fluid sealing issue? Not so fast, new problems crop up as the ring of compressive material thickens. Unless the gasket material is exactly as wide as the flange face, then the diameter difference will produce loading stress. The faces will actually deform and warp as the flange bolts are tightened. Furthermore, that stress won’t stay at the faces, it’ll propagate to a weak spot, perhaps a weld seam, where a hairline fracture could pop into existence.

Follow The Seal-Attenuating Determinants

It’s just common sense, the fact that a thicker gasket equals more gasketing material. Now the seal begins to suffer in other ways. Sure, the additional material provides more material plasticity, which means the tiniest leak-propagating irregularity is blocked. That feature comes at a cost, though. Thicker gaskets suffer from creep relaxation after their bolts are fully tightened. As a result of this issue, seal compressibility plummets. Viewed side-on, another dangerous problem makes itself apparent. There’s more material exposed to the open air, so a blow-out risk becomes likelier. Just to prove things aren’t all bad, though, thicker gaskets do work better in systems that have damaged flange faces.

Assessing The System-Prevailing Benefit

That’s right, thinner gaskets are not the preferred fixture when flange faces are uneven or poorly finished. Perhaps those surfaces are aging badly, or maybe they’re not perfectly aligned. Whatever the reason is, a thicker gasket acts as a force compensating device. If such unevenly applied forces or irregularity-plagued surfaces were handled by a 1-mm thick gasket, it wouldn’t counteract such flanging deficits. Switching to a 3-mm thick substitute, the thicker gasket fills the surface discontinuities while it also compensates for the unequally applied bolt loading forces. However, there’s still the blow-out factor and creep relaxation issue to consider.

A repaired gasket, fully realigned and milled flat, is the best answer here, but that solution isn’t always possible, not under real-world conditions. When such conditions transpire, a thicker gasket is the workable option, but it should use a reinforced material backbone, one that’ll resist creep, blowout hazards, and other such performance-altering determinants.

For any given sealing application, the correct gasket material and flange type are picked by an informed engineer. A fluid-suitable material is high on the features shortlist, for the gasket has to resist heat and chemical attacks. A tough seal structure comes next. It needs to be mechanically tough so that it can withstand great pressure extremes. Still, there must be more to leak management than flange types and gasket materials, right?

Flange and Gasket Geometry

Quite so, contemporary sealing technology is as much about surface contact profiles as it is about material compressibility. The flanges are stationary, although they do absorb massive amounts of kinetic energy as their bolts are tightened. Similarly, the gasket compresses but conforms to the shape of those twin sealing faces. The modulus of elasticity contained within the gasket material assures this essential leak stoppering effect. All the same, there’s always the remotest chance of a leak propagating pathway, behind which a fluid quickly follows. A raised face, followed by a gasket that incorporates a mild steel insert, stops unwanted leaks in their tracks. In effect, that softer steel is pressed beyond its yield point. With extreme bolt loads applied, the mild steel insert deforms so that it occupies every flange imperfection and leak propagation pathway.

Utilising the Correct Sealing Technology

Coming to the rescue, improved engineering practices produce mirror-like finishes. Those flange surfaces exhibit fewer surface imperfections, along with machine-sharpened profiles that tighten exactly against mirror-image gaskets. Like the old apparel makers used to say, “They fit like a glove.” There can be no gaps, no leakage pathways when such a fit is maintained. However, there are a number of real-world seal-attenuating influences that also require a technology-based solution. Thread friction, bolt creep and elasticity issues, these are just a few of the factors that technology can purge. Of course, a healthy measure of high-tech joint analyzing ingenuity also helps.

And that’s the key to this approach, the application of a leak analysis study. CFD (Computational Fluid Dynamics) modelling is of great use, as is the proper application of a pressure distribution simulation. Computers take over when such number-crunching duties beckon. All the same, the practicalities cannot be ignored. Proper bolt loading patterns are essential. Even so, such attention to detail means little if the threads loosen because of vibration or thermal expansion. Heat treated metals mitigate this effect somewhat. At any rate, flange materials, gaskets and fasteners are constantly under scrutiny. Always under development, external flange and gasket arrangements eliminate bend and orientation stresses. Inside those flanges, raised faces and composite rings counteract creep and elasticity changes.

Fluid temperatures and pressures are linearly applied. When that force hits a gasket, it strikes as either positive or negative energy. Vacuum or outward force, steam or cryogenic, the energies rise and fall. Sudden transient forces or cycling effects are a little different, of course, but they still impact system seals as energy. For chemical compatibility concerns, though, the situation changes completely.

Of Chemical Compatibility Matters

Granted, chemical causticity affects gasket materials. Beyond such singular cause-and-effect outcomes, however, there’s at least one additional causal factor functioning in a chemically incompatible gasket. A seal material’s backbone is susceptible to selected chemical formulations. Caustically aggressive or apparently material benign, it doesn’t matter. The fluid may even be a harmless oil, which feels slippery to the touch. No, what really matters is how a gasket’s molecular backbone reacts to the presence of a stated chemical.

Assessing Chemical Reactivity

Different materials react to chemical attacks in different ways. With certain alloys, the metal will break down and corrode. That’s why some fuels, ethanol among them, require special pipe metals. Aluminium and brass cannot be installed in ethanol-based fuel depots. Likewise, they don’t use cork-based gaskets and/or natural rubber seals. Yet these fuels don’t cause harm to biological tissue, not unless they’re ignited. Again, it’s the susceptibility of a particular gasket materials’ backbone that creates the threat here. To prevent gaskets from being eaten away by these seal-incompatible chemicals, a system designer has to know exactly how a specific chemical family affects a particular gasket material.

Gasket Design: Chemical Resistance

While one seal elastomer staunchly holds its form and features, an almost identical gasket dissolves into a useless ring of broken rubber. The material has lost its form, so it’s no longer capable of creating a reliable seal. Apparently, an acidic reaction has broken down the seal material. In truth, the chemical could just be performing as a catalyst. The molecular structure, covalent bonds and all, are then broken down as a consequence of this entirely natural action. To prevent such bond-breaking reactions, chemically resistant gaskets must be selected. These sealing materials stay inert and reactance-free when attacked by known fluids.

And that’s the crux of the matter, the fact that the fluid carrier must be a known chemical. Only then can the designer select a gasket material, one that’s chemically compatible and reactance resistant. Essentially, the seal material’s structure-retaining bonds stay inert when impacted by a known family of chemical agents. Best case scenario, a selected gasket substance should provide broad-spectrum chemical compatibility so that it has a better chance of resisting the many oils, solvents, and caustic chemicals that exist in this industry.