Things to Consider when Choosing O-rings

An O-ring, as the name suggests, is a circular seal or gasket with an O-shaped cross-section. The main function of the O-ring is to provide a tight hermetic seal against solids, liquids, and gases. O-rings are commonly used in products, process control systems, machinery, motor shafts, or other applications where sealing is desired. These applications can be dynamic or static. Although all O-rings are similar in design, there are different types. Here are five things to consider when choosing O-rings.

Temperature

Temperature resistance depends on the rubber chosen for the O-ring. Temperature resistance determines the ability of an O-ring to withstand extreme temperatures.

• High-Temperature: Viton® O-Rings, FFKM O-Rings, Kalrez® O-Rings, and Silicone O-Rings can resist temperatures up to 350˚C. This is an important feature for aerospace applications.
• Moderately high temperature: HNBR O-rings and EPDM peroxide hardened O-rings are suitable for relatively high temperatures up to 150˚C.
• Low-temperature: Silicone O-rings are preferred because they can withstand temperatures down to -60˚C.

Environment

It is crucial to become familiar with the application for which the O-ring is needed. This is crucial because we have O-rings available in different materials and sizes, such as FFKM O-rings, each with its own advantages and characteristics. Knowing the environment the O-ring will be exposed to will help you make an informed decision. Some environmental factors you should consider are:

• Ozone Attack
• Usage
• Vibration
• High ultraviolet radiation

Material

A failed O-ring seal often not only increases replacement costs but also machine downtime (which also entails significant costs). One way to extend the life of an O-ring seal is to ensure that its physical properties are at their best. Physical properties such as low compression, thermal aging, and oxidation resistance can extend O-ring life up to 3 times compared to low properties that are off the market. It is important to know the unique strength of elastomers, such as EPDM O-rings and Viton O-rings, which have the lowest compression set of all elastomers, or HNBR-O-rings and NBR-O-rings with the best mechanical strength.

PSI

Most O-rings are rated for pressures up to 1500 PSI. The pounds-per-square rating of an O-ring tells us the amount of pressure that the O-ring can withstand before leaking. At higher pressures, the material must have sufficient strength to withstand the compression of the clearance. O-rings have distinct combined limits for clearance, gap, material hardness, and system pressure differential. To prevent extrusion at high temperatures, reduce the extrusion gap, increase the hardness of the sealing material or add another ring to the O-ring if there is enough space.

Cross Section

The cross-section is the thickness of an O-ring. The cross-section of an O-ring determines its purpose. An O-ring with a large cross-section is generally used to prevent leaks. The cross-section of an O-ring is measured by turning it to its side. When considering the cross-section, the passages need to be regarded as well.

Harkesh Rubber’s sealing solutions are precisely calibrated with high-quality material and torque-reducing designs. Our O-rings have a high-pressure action that results in excellent sealing, all while operating with just the required amount of force. Get in touch with our industry experts to learn more.