As their name suggests, O-Rings — sometimes referred to as preformed packings — are doughnut-shaped gaskets that serve as seals. They need to be slightly deformed — that is, squeezed and stretched — in order to function properly.
Each side of an O-Ring is squeezed between the walls of whatever space the seal is going to occupy. This allows for zero clearance within the gland and creates an effective seal that precludes the flow of liquids or gases through the cavity’s internal passage.

Custom Molded O-Rings

A sealing system that’s been designed properly will always incorporate O-Ring compression. The position of an O-Ring depends on the level of pressure in the system. For example, a compressed O-Ring’s resiliency alone must provide the seal at atmospheric pressure. But when the pressure of the sealing system activates the seal, the O-Ring moves to the low-pressure side of the gland by force. This allows the O-Ring to fill any clearances, blocking the leakage of liquid or gas. In short, the O-Ring deforms to accommodate the needs of the system at hand.

Common O-Ring Applications

O-Rings are found in numerous industries, serving a wide range of application needs. These versatile components are frequently used in the following industries:

  • Fluid Power
  • Oil and gas
  • Medical
  • Aerospace
  • Industrial
  • Semiconductor processing
  • Consumer electronics
  • Food processing
  • Beverage dispensing
  • Water filtration
  • Automotive and trucking

To meet specific industry needs, O-Rings can be made from many different materials, utilizing various manufacturing techniques. Injection molding, compression molding, transfer molding, Liquid Injection (LIM) molding, extrusion and even CNC machining,  can all be utilized for the manufacture of O-Rings. Popular O-Ring materials include fluoroelastomers, nitrile, EPDM, silicone, HNBR, AFLAS®, and many other elastomers.

To ensure O-Ring seal design accommodates your exact needs, it’s important to consider quantity and cost, of course, but application temperature, chemical compatibility, lubrication, and sealing pressure should also be kept in mind.

O-Ring Sizing

Precision Associates offers one of the industry’s largest collections of special sized O-Ring tools. Currently, we have over 2,600 different-size O-Rings in production, and we typically add a new size each week. Our comprehensive O-Ring size chart can help you determine the correct size for your application.

Working With Precision Associates

Precision Associates is proud to provide highly reliable, top-of-the-line seals and other precision molded rubber products, such as X-Rings and U-Cups. We can manufacture parts in a range of sizes, from 36 inches to micro-miniature.

Curious to learn more about our O-Ring offerings, or ready to discuss your unique sealing needs with an expert? Reach out to the team today.