Popular O-Ring Applications in Industry and Manufacturing

What Are O-Rings?

O-rings are mechanical gaskets that seal against fluid pressure in pipes and other types of tubing. Because of their relatively low cost and ease of installation, many industries use O-rings for a variety of applications to prevent the unwanted flow of fluid (liquid or gas) in components such as pumps, pipes, pistons, and valves.

J.O. Lundberg patented the first O-ring in 1896. However, O-rings weren’t commercially available in the United States until Danish-born machinist Niels Christensen patented his improved process in 1937. After the onset of World War II, the US government determined that O-rings formed an essential component of many war-related products, and it sponsored their mass production during the manufacturing boom that followed its entry to the conflict.

Manufacturers place these small toroid-shaped (or O-shaped) devices in the groove between two mating surfaces. The mating surfaces easily compress the ring due to its rubber-like elastic properties, thus forming a positive seal between them that prevents fluid movement between the surfaces.

How Are O-Rings Made?

Manufacturers build O-rings using a variety of machining techniques including extrusion, pressure molding, injection molding, and transfer molding. The selected manufacturing method primarily depends on the material used to construct the components as well as the desired level of performance.

• Extrusion — Intense pressure forces the O-ring material through the shaped opening of a die. The material emerges on the other end of the die in the desired shape, and then workers or automated processes cut it into specified lengths.
• Injection molding — Manufacturers inject molten material into a mold, where it then cools into the requisite O shape. Although commonly associated with metal, this technique also produces O-rings from a wide variety of elastomers and thermoset/thermoplastic polymers.
• Pressure molding — Workers place preheated elastomer or polymer material in a heated mold cavity. The other half of the mold closes on the material, further applying heat and pressure until the mold material has cured.
• Transfer molding — Applied pressure forces material into a mold. Unlike injection molding, transfer molding uses significantly higher pressure to fill the mold cavity.
  O-rings can incorporate a large number of materials, each with specific properties lending itself to different applications. Some of the most common O-ring materials include nitrile rubber, silicone, polyurethane, neoprene, and fluorocarbon.

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