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O-Rings

O-Rings

Buna-N, Viton, silicone and EPDM O-rings by AS568 dash number.

Also searched as: o ringsas568viton o ringbuna nnitrile o ring

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About o-rings

O-rings are toroidal seals, typically circular in cross-section, designed to be seated in a groove and compressed during assembly to create a seal between two or more parts. They are critical components in static and dynamic sealing applications across various industries, preventing leakage of fluids or gases. Selection is primarily driven by the application's operating conditions, including temperature, pressure, and chemical compatibility. Standardized dimensions are defined by specifications such as AS568, which specifies inside diameter, cross-sectional diameter, and corresponding dash numbers. Common materials include Buna-N (nitrile) for general-purpose applications with good oil and solvent resistance, Viton (FKM) for high-temperature and aggressive chemical environments, silicone for extreme temperature flexibility and medical applications, and EPDM for excellent resistance to steam, hot water, and brake fluids. Material choice significantly impacts performance characteristics like durometer (hardness), tensile strength, and compression set. The correct O-ring ensures long-term sealing integrity and system reliability.

How to choose

Selecting an O-ring involves a sequential decision process. First, identify the chemical compatibility requirements based on the fluid or gas being sealed; this dictates the base polymer (e.g., Buna-N, Viton, EPDM, Silicone). Second, determine the operating temperature range to ensure the chosen material maintains its sealing properties without degradation or embrittlement. Third, consider the pressure differential across the seal; for high-pressure applications, consider backup rings or harder durometer O-rings to prevent extrusion. Fourth, specify the required dimensions, typically by AS568 dash number, which defines the inside diameter and cross-section. Finally, assess whether the application is static or dynamic, as dynamic seals require materials with lower friction and higher abrasion resistance.