A metal o-ring is a device shaped like a disc and is primarily used for sealing purposes. They are placed in items such as pipes, tubes, vacuums, and valves to function as an impermeable blockage within a joint that prevents liquids and gases from passing through. Metal can be used in joints with either static or dynamic compression, though it is more suitable for the former. Once in place, a metal o-ring creates a four-point seal within the joint, which is an ability unique only to o-rings made from metal. Metal o-rings are robust, have high-integrity dealing, and have many options for plating and tubing with ventilating options available.
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Many industries use metal o-rings. For example, they are used for applications in the aerospace industry involve factors such as close or exacting tolerances, high temperatures, fatigue resistance in engines and machinery, and extended chemical exposure. Another example is the nuclear industry. The nuclear industry involves applications that run the risk of radioactive leakage. These applications have a set of requirements as to which sealing systems work better to lessen these concerns.
Additionally, the semi-conductor and vacuum industries have become a vital part in modern society, because they play a crucial role in the manufacturing of cutting-edge products. These high-tech, state-of-the-art pieces of equipment—such as computer chip processing equipment and fuel cells—require uniquely-shaped seals to keep them functioning properly. Metal o-rings assist in alleviating concerns such as noise, emissions, and even maintenance costs in these applications. Manufacturers of o-rings work closely with all of these industries to make sure their specific needs are met.
Although elastomers are a popular choice of material for the production of o-rings, there are several characteristics of metal that makes it more suitable for some applications. Unlike elastomers, metals are more resistant to corrosion, pressure, and temperature. Metal o-rings can also feature plastic jackets that make full contact with the item as an alternative to the four-point seal. As the joint compresses and changes shape, the plastic coating can spread, filling any cracks and gaps that may occur in the surrounding materials. In addition to added plastic features, metals such as carbon are commonly utilized to prevent static sparks and electrical arcing in elastomer compounds.
- This type of metal o-ring is not pressure-filled or self-energized, and is recommended for applications with low to moderate vacuum ratios and pressure levels, as higher pressure levels may cause the tubing wall to collapse.
- These metal o-rings are designed for high pressure applications. Small holes are drilled into the wall of the tubing, exposing it to the pressure in the system. These ventilation holes relay pressure inside the pipe or container in order to achieve enough pressure to adequately seal it., and thus reduce the possibility of the tubing wall collapsing.
- Like self-energized O-rings, these metal o-rings are for applications that require sealing at high pressures. They are filled with an inert gas which increases in pressure relative to the increase of temperature in the system. This creates an energizing effect that partially makes up for the loss of the machine’s material strength while in operation.
Metal o-rings are all fabricated by die casting, and can be made from materials such as gold, inconel, steel alloys, copper, silver, nickel, and aluminum. Plastic-based o-rings are also available, which are typically fabricated from synthetic rubbers such as silicone or viton. O-rings can also be plated or coated with metals such as indium, silver, gold, nickel, copper, cadmium, and Teflon, in order to make them stronger, more fitted, or more corrosion-resistant. Metal o-rings can then undergo further treatments including annealing, age hardening, or heat treating.
The type of material and the required finishing processes are determined by the application for which the metal o-ring can be used. For example, heavy liquids typically do not require coating, but gases such as helium or hydrogen that are more volatile should be handled with extra care. If an o-ring that contains volatile fluids is coated, it serves as a safety measure and can improve the quality of the seal.
Metal o-rings function best in temperatures ranging from -450°F to over 1300°F. Therefore, in choosing the right material for a top coating, one must consider the application’s temperature requirements. In addition to temperature range and type of coating, other considerations include diameter, vacuum range, and pressure range. Since o-rings are an important component in ensuring that a machine operates safely, they must undergo thorough dimensional and visual inspection.