Acids and oils course like water through wide channels. And although the compounds aren’t as toxic as those found interred inside chemical processing plants, that doesn’t mean they can’t eat their way through a rubber gasket. That’s why the food industry can’t operate for long without food grade gaskets. Anything less, well, those corrosive fluids will eventually eat away their material bases.
Seal Materials That Frustrate Food Corrosiveness
Some rubbers deteriorate when they’re exposed to acids. Other materials, they break down when heavy oils are present. Granted, the fluids here are mildly acidic, and those oily fluids are nothing more than animal fat or vegetable oil. Still, in food grade applications, those seals are exposed to acids and oils 24/7, all year round. The liquefied foodstuff could also be hot or chilled, so the selected food grade gasket better provide plenty of chemical resistance strength.
Generally speaking, gaskets that are designed to satisfy the FDA (Food Drug Administration) standards and the FSANZ (Food Standards Australian and New Zealand) lack the additives that are commonly injected into most sealing products. But let’s leave this feature alone, just for the moment. The gaskets are die cut from sheets of silicone and nitrile, from modified PTFE and other food safe gasketing rubbers. Oftentimes, for maintenance and sanitizing reasons, the industry opts for a standardized style, a white or translucent sheeting material. Clearly, then, there are weighty issues in play.
Comprehensive Gasketing Solutions
The foodstuff in the pipes could be waste, could be some stringy residue, but it could also be headed for a jar or can, which then hits the highway on the back of a truck as it heads to market. As such, food grade rubber needs more than the system-beneficial chemical resistance feature mentioned earlier. Those seals must also guarantee a food safe build. Remember, pickling juices, vinegars, oils, and salts break down gaskets, but that action occurs slowly. This is what’s known as the food leeching effect. Going back to additives, the plasticizers and fillers touched upon in the previous paragraph, food safe gaskets cannot incorporate such additives, not if they’ll end up migrating into the edible stream.
Food safe and food-proof, the rubbers used in this mildly corrosive industrial and commercial application are designed to retain their fluid sealing features and elastoviscous characteristics, even when a strong vinegar, citric acid, or salt is conveyed. Beyond that key feature, of course, the rubber gaskets, be they nitrile or silicone, must be designed to neutralize the rubber leeching effect, for this is a consumables stream, a product that’s meant for human consumption.
If a smaller O-Ring gasket ends up in the beefy hands of an installer, it’s hard to ignore that slight form. How can this seemingly trivial system component ever hope to provide sealing strength? Well, for starters, this sealing component has more geometry than a conventional gasket. It’s shaped like an emaciated doughnut, but looks can be deceiving.
The Secrets of O-Ring Gasket Strength
In truth, that geometry, the torus-like structure of it, is designed to deform uniformly when it’s placed into its cavity. Gaskets act similarly, but the compressive forces applied to those rings moves linearly along one dimension, perhaps two if we incorporate flange twisting forces. Squeezed into its companion gland channel, the flexible O-Ring material compresses equally and in every direction.
Primary Installation Tips
Going on the above passage, the first piece of advice is to ensure the rubberized ring is properly inserted into its matching cavity. Remember, the rubber is designed to be compressed radially during the installation phase. If it fits loosely, then this isn’t the right O-Ring for the job. Similarly, the diameter of the uniformly shaped band should be slightly smaller than that cavity, because the flexible material is meant to be stretched as it’s fitted.
When the cross-sectional area issue and ring diameter problems are sorted, the loop of rubber fits snugly. But does the material ring come equipped with the right fluid-handling specs? Chemical attacks are likely, temperature extremes are probable, and pressure variables certainly can’t be ignored. Select an elastomer, a silicone, neoprene, nitrile, or other fluid compatible material that will endure when it’s assaulted by any or all of these fluid forces.
Understand Application Tolerances
O-Rings can be used in static applications or in systems that employ dynamic fluid pressures. Select a product accordingly, one that fits a fixed flange or a dynamically capable variant that can conceivably function in a system that uses reciprocating cylinders. Next, avoid cross-sectional rolling. If the application does use an awkwardly located gland channel, then the installer may end up twisting or kinking the ring when it’s being fitted. Always avoid O-Ring twisting.
Check the work after the fitting is coupled. Is there an extrusion protruding from the channel? Undo the pipe, replace the O-Ring, and try again. Last of all, do understand the different elastomers, the alternate ring application usage spheres, and the knock-on effects on each and every equipment type. Is this pneumatic equipment? Is there a reciprocating cylinder riding behind the O-Ring? Essentially, this fitting is indeed slight, but its geometry and material base will operate efficiently as long as the fluid conditions and ring specifications correspond.