Gaskets, especially those used on industrial equipment, prevent fluid leaks. The sealing rings are fitted between pipes. They’re also installed between pipes and their fittings. On hoses, in pressure vessels and fuel tanks, on fluid processing equipment, all of these fluid-networked parts require gaskets. To all intents and purposes, the seals are mechanically durable, but that one leak-stoppering feature isn’t enough, not on an industrial equipment line.

Heavy Industrial Energies Propagate

Suppose you’ve talked to a system designer, and that expert builds industrial equipment frameworks. The equipment and pressure vessels are the building blocks that contain near unimaginable energies. And those forces aren’t static. Temperatures rise when catalysts cause state changes. Valves alter pressures while other components aid liquids during their vaporization cycle. High temperatures and higher pressures press hard against the internal surfaces of the equipment. Put simply, while it’s true a mechanically sound gasket will withstand kinetic energy, other energy forms can cause damage.

Stressing Gasket Material Importance

And you haven’t even heard the engineer talk about chemical attacks. Potentially, after adding chemical attacks to the mix, the number of gasket-weakening factors in play goes through the roof. It’s hard to find a gasket material that’ll stop multiple process forces, although resilient PTFE seals are a fine option. Even then, compressive forces can introduce Teflon creep. Elsewhere, Neoprene and Nitrile based rubber rings defeat most oils and fuels. Finally, for harsher chemicals, higher pressures, and great temperature extremes, there are metal inserts and/or compressed graphite rings, which come with their own lists of performance pros and cons.

Solving Fluid Adversity Issues

External influences are easy enough to assess. If the pipes and fittings are installed outdoors, a matching set of gaskets must be UV resistant and weatherproof. However, when scores of dynamic fluid factors flow in a pipe, things get more complicated. Still, pipes and storage units don’t typically create new form-impacting forces, not by themselves. Switching over from a simple storage line, industrial equipment is added to the system. Now there are pumps and heat exchangers, plus a dozen other active assemblies in the line. To handle these aggressive streams, the equipment designer upscales everything, including the gasket materials.

Incidentally, an oil resistant gasket won’t stop every type of oil. Likewise, a Teflon seal won’t stop every acid, nor will it resist every caustic chemical. You see, there are hundreds of different chemical reagents and oily substances in use on various industrial facilities. Even the finest gasket material can’t deliver absolute sealing performance, which is why you need access to material data sheets and fluid formulations before choosing a gasket. Poring over those sheets of literature, gasket selection accuracy pays off handsomely.

Polytetrafluoroethylene is a man-made compound that serves the flange sealing industry very well indeed. PTFE, to use the synthetic material’s abbreviated title, is a thermally stable material. Gaskets made from the fluoropolymer also feature a high level of chemical resistance. Hot and chemically caustic fluids simply slide past the ring gaskets without impacting the substance in any way whatsoever.

Thermally Steadfast Gaskets

This is a substance that was famously utilized in the Apollo space program. Known universally as Teflon, the incredibly versatile substance can withstand the heat that’s generated by atmospheric reentries. A more prosaic application, which of coating frying pans, still manages to show off the fluoropolymer’s heat handling talents. Turning towards gasket rings, PTFE seals maintain their finest sealing features when fluid temperatures rise to 204°C. Alternatively, the synthetic plastic won’t become brittle when a fluid medium turns frosty. Down to as low as -73°C, its visco-mechanical properties remain unchanged.

Resists Chemical Causticity

Engineers hate generalities. So PTFE is imbued with superior chemical resistance, but for what chemicals? How well does the gasket ring substance perform when a truly concentrated acid flows? Will a super-caustic fluid eat its way through the fluoropolymer? Well, Teflon performs admirably when it’s attacked by acids, alkalis, alcohols, and solvents. It’s a remarkably non-reactive material. Even oils and greases, those that weaken other rubbers and plastics, rarely affect PTFE gasket rings. To find any weaknesses, research Teflon gaskets and fluorinating agents. These compounds do cause trouble for the material, as do certain alkali metal bases.

The Thermal and Chemical Benefits

At twice the boiling temperature of water, such steamy outflows scorch and carbonize lesser plastics. PTFE retains its mechanical attributes and its viscoelastic talents when this level of thermal hostility burns its way down a pipe. In real-world chemical processing, the attack rarely comes from one direction. More commonly, at least two, often three, forms of attack occur simultaneously. In other words, expect the high temperatures in a chemical processing plant to be accompanied by a caustic assault. Fortunately, thanks to a non-reactive carbon backbone, PTFE gaskets easily reject both forms of attack.

Other benefits crop up as the material advantages list is examined. This is a hydrophobic plastic, so it rejects fluids. PTFE gasket rings also possess a low-frictional coefficient, which means they’re slippery. Placed properly against a flange face, the opposing face fits snugly, without generating any abrasive opposition. In summary, PTFE gaskets are the chemically resistive kings of the fluid sealing realm. Better yet, though, they’re descended from a material lineage that’s designed to operate under all kinds of temperature extremes.

Elastomers are clearly malleable but not flimsy. They’re compressible, not fragile. You see, just because an elastic seal can deform, that doesn’t mean it’s mechanically weak. It’s the same with chemical resistance, a feature elastomer gasket materials possess in abundance. Stretchy cross-linked molecular chains deform and recover while they repel the effects of corrosive chemical attacks. However, to deliver enhanced seal compressibility features, tradeoffs are sometimes made.

A Balanced Set of Gasket Features

By tradeoffs, we’re talking about a loss of one material characteristic while a second property is enhanced. In gasket design, the compressibility factor ranks high, so other design characteristics can fall by the wayside. Well, this design faux pas cannot be permitted, especially on a seal that requires a balanced set of fluid containment attributes. For example, a high level of material compressibility is all very well, but it won’t help if a high temperature weakens the elastomeric bonds. Similarly, a deformable gasket isn’t much good if it lacks an all-important ability to resist harsh chemicals.

Utilizing the Right Elastomer

So the application in question uses high sealing energies, as applied by a series of encircling nuts and bolts, to squeeze an elastomeric gasket. The fluid rushing through the pipes isn’t likely to escape. Looking down the ingredients list of that fluid, however, it contains a corrosive acid. Mechanically sound or not, this caustic chemical will make short work of a seal that doesn’t feature a chemically resistant build. Generally speaking, EPDM and Viton based gaskets provide sound elastomeric resistance. Fluoroelastomers perform well when acids are around. Silicone gaskets, well, they’re more susceptible to acids, but they hold up well when attacked by oils. Likewise, nitrile and neoprene seals remain unaffected when oily substances attack.

Using Chemical Resistance Tables

Complex molecular chains stretch and recover when elastomer gaskets squeeze between two flanges. Importantly, while one part of the chain may stubbornly repel a lubricant or chemical reagent, a second linkage could weaken. Simply put, this is a tricky field of study. Making things worse, there are hundreds of different acids and oils, which will affect different gasket materials in different ways. To determine those effects, we need a chemical resistance table, a datasheet that contains a list of hundreds of chemicals. Running a finger down the table column, we can see how any single chemical will impact a chosen elastomer.

Elastomer science is ruled by hundreds of advanced bonding conventions. Cross-linked and deform-capable, the malleable materials react according to seemingly unfathomable physical laws. Check a gasket datasheet to see if it’s specced as a chemically resistant material. Which oils or acids does it specifically repel? For more information, contact the gasket manufacturer or grab a copy of a chemical resistance table.

Imagine the following unacceptable case study. An O-Ring is seated within an equally sized groove. What’s wrong with this picture? Well, the rubber won’t compress as it’s installed. Instead, the identically sized O-Ring and circular groove create a snug fit. An effective seal can never form. To create that seal, the cross-sectional width and depth of the ring must be sized so that it’ll compress as it’s installed, and here’s why.

Creating an Effective Seal

Generally speaking, it’s true, thicker rubber loops compress and produce better seals because they’re slightly larger than the hardware they’re entering. But engineers don’t work on general principles, which is why this squeezing effect requires intelligent management. Specifically, seal integrity is governed by what’s known as an O-Ring’s squeeze ratio. It’s a figure that’s expressed as a ratio. It can be found by comparing the amount of material deformation that takes place within a rubber ring as it’s pressed into its curving groove. In engineering terms, the free-state cross-sectional density and installation deformation volume are compared and expressed as a ratio.

Deform-Proficient Rubber Matrices

Looking deeper inside the rubber loop, the specially engineered elastomer is seen to gain energy as it’s compressed during the ring seating stage. The rubber matrices squeeze together and absorb energy. In response to this action, the material pushes outwards as it’s pressed into a smaller space. Those surfaces press hard against the hardware groove. In plain English, the rubber forms a formidable seal because that absorbed energy is seeking some kind of outlet. It’s this deformation factor, the inherent elasticity of the compressed O-Ring, that’s measured as a seal’s squeeze ratio. Importantly, by selecting the correct material and ensuring that the product comes with an intelligently selected cross-sectional density, the right O-Ring squeeze ratio is singled out each and every time.

More is better, at least that’s what people are taught. For engineering professionals, that’s not always true. An optimally rated squeeze ratio creates a solid seal. Pushed beyond a certain point, though, the sealing energy is transformed into stress. Friction and seal wear occur when such stresses abide. Worse still, pinch points weaken, the walls of the groove crack, and the seal becomes compromised. To sum up, if the cross-sectional thickness is too small, excess elastic stress causes too much material deformation. Sized to match the hardware groove, seal integrity is woefully inadequate. Finally, with too much squeeze, an overly thick O-ring will weaken, or the walls of the groove will crack. Overstressed, the pinched, worn or weakened seal creates tiny pathways, gaps where pressurized fluids will leak.