Low-pressure pneumatic systems employ less than 75-kPa of pump compressed air. That figure can climb as high as a several hundred kilopascal load. For hydraulic equipment, the design engineer can easily pop another zero on the end of that number, for these heavy-duty systems are often asked to handle thousands of kilopascals, and those kinds of fluid loads are unforgiving, at least when it comes to a leaky gasket.
Demystifying Fluid Mechanics
As a central premise, capable hydraulic and pneumatic gaskets are designed to keep compressed gasses and pressurized liquids within fluid power equipment. The equipment employs a closed loop, with the contained fluid forces conveying energy from pumps and reservoirs to onboard actuators. Those actuators include rod and piston devices, plus several branching families of force manipulating component classes. In fact, just like electrical equipment, a whole science has sprung up around fluid transmission technology. There are complex circuit elements in the systems, plus numerous feedback-controlled network forms, many of which are built to responsively turn small signals into proportionally larger mechanical actions.
Essential Qualities For Fluid Power Transmission Gaskets
Clearly, thanks to the immense contained pressures, a leaky gasket represents a major health hazard. From one point of view, the energy losses impact machinery. The gear becomes less responsive, an outrigger fails on a crane, there’s a chassis-toppling risk, and the boom of a heavy lifter could fail at the worst possible moment. More directly, tiny leaks act like invisible jets, which can send fluid rocketing towards an unprotected eye or someone’s skin. Forcefully ejected fluids can easily penetrate soft tissue and cause serious physical harm. Unfortunately, there’s no way around this danger, not without a high-quality gasketing series. Conforming to the irregular surfaces of a pneumatic or hydraulic tube interface or flange, quality gasket seals fill microscopically tiny mating surface voids. Installed correctly, though, o-rings and flat-faced gaskets stop fluid leakage effects in their tracks.
Unique among other equipment forms, hydraulic and pneumatic equipment handle huge loads, but they’re also built to function as clean closed loop systems. That’s a tough restriction to solve. No pollutants can enter from the outside, no oils or water, air or particulates. Meanwhile, hydraulic oils can be corrosive while pneumatic gasses suck in large quantities of system-corroding moisture. The selected gaskets can’t fail when they’re attacked by corrosive oils or parts-fatiguing water, nor can they break down if the fluid emulsifies. Heat and pressure, plus a slew of other system-impacting variables are waiting for their chance to damage the fluid seals, so high-quality gasket seals are a must-have feature.
When seeking low-temperature gaskets, coolroom designers use their engineering skills to select suitable materials. A conventional sealing material, although compressible and surface conformable, isn’t necessarily good enough here, not if it becomes brittle when the temperature drops below zero degrees Celsius. Clearly, then, as well as all of the normal, highly desirable material compressibility features, freezer gaskets require a little something extra.
Studying Seal Fracturing Events
If a freezer seal does harden and become inelastic, then the slightest amount of material expansion will be enough to cause a sealant crack. All it takes is one tiny crack. Such fractures grow, they propagate until they compromise energy-efficient freezers and coolrooms. It’s impossible to stop a material from expanding then contracting, and it’s impossible to eliminate compressibility stress. It’s also plainly impossible to eliminate door seal strain, as caused by a forcefully closed coolroom entryway. Spring-loaded door closers help, but the mechanical stress still works its way into the portal gasket. As for the other system seals, there’s just no avoiding the material-deforming forces that are pushing down on their stiffening forms.
Equipped With Freeze-Resisting Resilience
To be brutally honest, those gaskets must endure, even when the enclosure temperature dips far below freezing point. Logically, then, if the cold is unavoidable, what can be done to fix matters? There are heating elements of course, which are designed to protect door gasket elasticity. Better yet, though, system designers opt for gasket materials that feature low-temperature performance. In profile, the door gaskets mentioned earlier tend to be manufactured out of extruded silicone. Double or triple layered, the strip geometry conserves energy. As a heavily reinforced door closes, the folded silicone uses an air cushion to protect the compressible rubber so that it squashes evenly all around the door frame. Expect this material to function when the enclosure temperature drops as low as -60°C. Of course, few freezers and no coolrooms require this degree of ultra-low elastomeric performance.
Silicone and PTFE gasketing materials retain their squashable features, even when they’re used in cryogenic applications. For more conventional applications, however, soft PVC, nitrile, and other synthetics are acceptable. Other desirable features, ones that play a role in the decision-making process here, include pressure handling capabilities, tensile strength, and even an aptitude for accepting magnetically charged additives. Easy to clean, not impacted by popular cleaning chemicals, and unaffected by sudden temperature spikes, the chosen gasketing elastomer should also be die-cut congenial and extrusion tool friendly. Incidentally, since coolrooms and freezers contain oil-laden foodstuffs, the selected rubber should be as oil-resistant as it is low-temperature capable.