Extrusions are discharged through special die assemblies. The elastomers are loaded into extrusion machines, heated and forced at pressure, then they slide through the die section, where they’re shaped into a desired cross-sectional outline. Continuing outwards, like toothpaste from a tube, the die-profiled extrusions assume many functional shapes, including those that have edge trims.
A Side-On Viewpoint
Viewing this gasketing medium from the side, we see its extruded profile. In one case, the synthetic rubber has been heated and pressed through an ‘H’ shaped die. There’s a curved notch on the lower half of the rubber lining, plus a subtly different notch located on the top section. Picture this material formed into a framing shape or a ring. For a custom-fabricated gasket, it precisely fits two mating surfaces because the die was perfectly profiled. For a glazing seal, the material stretches slightly when panes of glass slot into place. And that profile, the ‘H’ shape, isn’t alone. Indeed, there are limitless options here, including U-channel extrusions and hollow-tubed variations.
Extrusions: The Different Types
Materially, neoprene and EPDM rubber gaskets dominate the industry. Silicone variants and Viton alternatives are also available. Whatever the material choice, it must suit its application. Utilizing a die insert, the extrusion equipment profiles the tubular or flat-formed material lengths. U-shaped channels are squared or squeezed into ovals. For tubing seals and D-shaped inserts, there are die plates to accommodate those profiles, too. Essentially, there’s a limitless number of extrusion shapes available, each of which satisfies one of a thousand applications. However, there are material limitations and client parameters to regulate the material/shape selection process. Let’s look at those now.
Shaped By Material Limitations
Unlike geometrical shaping, this form-fitting approach depends on the application domain. For example, glazing extrusions, ones used in the automotive industry, should always source weather and UV resistant rubbers. Likewise, an extruded gasket, perhaps destined to suit some high-altitude aerospace application, won’t satisfy a client if it can’t retain its gasket-compressing capabilities when the temperature turns icy cold. Indeed, unlike pipe face gaskets, extrusions are more geometrically intricate, so a capacity for keeping that shape when attacked by the harshest environmental and/or mechanical forces ranks high here, especially when a potential seal discontinuity represents a substantial application or user hazard.
This is a second but equally relevant branch of the gasketing tree. Instead of die cutting entire shapes from a sheet, the material is pressed by a hydraulically powered piston through a toughened die. Heat and pressure are the driving forces here, and they produce some amazingly feature-rich, cut-to-length seals and gaskets. Arguably more flexible than their ring-shaped gasketing peers, extrusions assume countless cross-sectional profiles.
Full face gaskets are wide enough to cover an entire flange. That means the ring starts at the edge of the flange face, moves in towards the internal pipe diameter, and thus covers the whole seal surface. Securing bolts pass through the gasket, so there’ll be bolt holes included on the die-cut material. Talking of materials, Viton is the selected base here, with its fluoroelastomer-backed features dispensing heat-resisting resilience.
Outstanding Mechanical Performance
Applications include processing constructs that carry pressurized petroleum-based fluids. In large-scale pipes, oil refinery zones and fuel depot sections convey corrosive oils and fuels. In here, Viton type full face gaskets retain their sealing characteristics when they’re exposed to high pressures. Similarly, in chemical processing environments, the ring gaskets, compressed by circles of tightened fastener bolts, refuse to be impacted by dynamic state changing events, as encountered in catalyst-rich processing plants.
Heat Resistance Applications
Heat exchangers use streams of pressurized steam to warm independently connected heating networks. Stack and tube configurations channel the steam in, the second stream of cooler water is warmed, and the system works its heat exchanging magic. Thanks to Viton’s high-temperature capabilities, full-face gaskets made from the fluoroelastomer perform grandly in boiler-side applications. If the steam is super-pressurized or carrying hundreds of degrees of thermal energy, it just won’t matter; the bolt-tightened Viton sealed flanges will safely and surely channel the super-hot (+200°C), super-pressurized fluid. Granted, a regular Viton gasket can also manage high-temperature fluids, but blowout dangers are more likely when these seals are selected. To manage high temperatures and higher pressures, the design engineer opts for a stronger, more resilient solution. And that’s where Viton full-face gaskets enter the scene.
Chemically Based Heat Exchangers
Since Viton features moderate low-temperature capabilities (-20°C), let’s stick with the synthetic rubber’s heat-biased applications. In the above paragraph, heat exchanger technology was discussed, but the usage domain was strictly limited to hot water. That’s a popular and essentially important industry, but heat exchangers are also employed in the chemical processing sector. Efficiently isolating two or more chemical phases, Viton seals resist this triple threat. They contain heat, retain their mechanical form when high pressures flow, and they also handle incredibly corrosive chemical reagents. That three-way threat exists in chemically-based heat exchangers, so Viton full-face gaskets are also on-hand to manage the multiple fluid hazards.
Skipping up a level, flanges assume raised faces. Meanwhile, flat-surface or full-faced gasketing applications demand a compressible but rigid material base. Cut with bolt holes, the fluoroelastomer isn’t weakened by those rings of fastening apertures. To the contrary, they function with reinforced heat and pressure resisting strength across countless industrial applications.