Environmental conditions play a significant role in the effectiveness of O-ring performance. The effects of weather on an O-ring and the ozone can easily impact the integrity of the seal, leading to failure. Though the doughnut-shaped rings are well-suited for the most demanding jobs, adverse conditions such extreme heat or cold, degrees of moisture—wet, rainy, or humid environments—or ozone exposure are factors that influence an O-ring’s effectiveness.
O-rings consist of a wide range of robust materials that provide reliable seals for many applications vital to industries and industrial systems. Materials are derived from a type of elastic polymer, an appropriately named synthetic rubber product known as an elastomer. As with any polymer, its mechanical properties can be enhanced to meet its application requirements.
In the case of O-rings, the range of applications is only as effective as the mechanical properties they hold. Flexibility, elasticity, tensile strength, resistance to corrosion, stress, or tears, and absorption are important considerations. Yet, to achieve optimal performance, O-rings must first meet the challenges posed by the environmental conditions in which they are applied.
Effects of Extreme Weather on O-Rings
Here is what can happen when O-rings are subjected to intense weather conditions and ozone exposure:
Temperature, whether high or low, can affect synthetic rubber material. In hot, humid climates, when temperatures rise, rubber is subject to deterioration. In high-temperature applications, extreme heat can cause chemical changes to occur to the material over time. It causes material degradation and deterioration. Chemical changes, by nature, cannot be reversed when the temperature cools. Whether it is subjected to elongation or the material’s tensile strength, the change is permanent, and the seal is no longer compatible with the system.
For specific high operating temperatures, O-ring material choices include:
- hydrogenated nitrile
- silicone rubber
Cold weather can cause rubber to lose its elasticity, which can affect the elastomer’s compression set—that percentage of the material that fails to return to its original size after being subjected to compression. Elastomeric compounds must support a sub-degree service temperature, or they will fail. Low temperature causes elastomeric materials to contract and become less flexible, even brittle after prolonged exposure. As compression set worsens in low temperatures, it will not return to its original size, which will result in seal leakage and ultimate O-ring failure.
O-rings materials manufactured for extreme cold applications include low-temperature nitrile, HNBR, low-temperature silicone, FEP/PFA, FFKM, EPR, and Astra.
Though one of the prime applications for seals is preventing leakage of fluids, ironically, too much water—moisture, high humidity, or rainy weather—can present problems that lead to excessive swelling of the O-ring and, eventually, result in seal failure. Excessive moisture affects a seal like a sponge, to the point where the swelling modifies an O-ring’s mechanical and physical properties. Eventually, it alters the sizing between the seal and gland. The sponge-like effect causes the seal to become incompatible with the system environment and malfunctions.
In wet, rainy environments, select an O-ring material that is compatible with a wet or humid environment such as Viton, EPR, or nitrile.
Ozone is a gas derived from oxygen and is found throughout the earth’s atmosphere. The stratosphere protects life on earth from the sun’s UV radiation in the upper level. Near the earth’s surface, ozone presents several issues beginning with its ill effects on human health. It also doesn’t interact that well with rubber seals of any kind. Even in the smallest concentrations, ozone attacks on O-rings can result in deterioration and cracking of the material.
Ozone exposure is usually caused by ultraviolet light, electrical arcing, and electromagnetic fields common to many manufacturing and industrial environments. Before installation, O-rings should be stored away from electrical equipment or motors. They should also be kept in a dark room away from fluorescent lights or direct sunlight. Before fitting an O-ring, lubricate to protect them from ozone. In application environments where long-term ozone exposure is high, use O-rings made from ozone-resistant materials such as EPDM or fluorocarbon.
Successful sealing systems begin with selecting the right material for the application. O-rings must first be able to withstand harsh environments, temperature extremes, and ozone degradation for optimal performance. To adequately meet your sealing application requirements, consult with an expert at Manufacturer’s Rubber & Supply to ensure you have the right seal for the job.