Due to the complexity that characterizes the process industry, fluids that can be aggressive for the sealing elements in valves, such as O-rings, are often used. This is explained in another article published in our blog: “Some sealing solutions in valves”.
O-rings are manufactured from elastic materials, also known as “elastomers”. The most common elastomer materials are usually:
- - Synthetic rubbers such as EPDM and the NBR.
- - Silicone rubber (VMQ).
- - Fluoroelastomer rubber (FPM).
- - Perfluoroelastomer FFPM, among others.
Index
Ethylene propylene diene rubber elastomer
It has a excellent performance with water vapor, The tightness of this fluid is not at all easy. We even offer you a special formulation of EPDM, capable of working up to 288 ºC with water vapor in an anaerobic environment, i.e. free of oxygen. In addition; shows resistance to atmospheric ozone, weathering, alkalis, acids, bases, polar solvents, ketones and ether-glycol-based brake fluids. The elastomer limitation of EPDM is not suitable for sealing oils, greases, aromatic and chlorinated hydrocarbons, as they severely attack it.
Acrylonitrile-nitrile rubber elastomer
Presents good chemical resistance to hydrocarbons, mineral oils, mineral oil-based greases, animal and vegetable fats, water up to 100 ºC, inorganic acids and bases in low concentrations. In the presence of fuels with high aromatic content, the resistance of the NBR elastomer decreases and it is clearly attacked by ozone, weathering, aromatic hydrocarbons, chlorinated hydrocarbons, esters, polar solvents, strong acids as well as ether-glycol based brake fluids. We have a special NBR for low temperature applications, capable of working down to -60 ºC.
Silicone rubber elastomer
They stand out for their high thermal resistance and good cold flexibility. The use of silicone rubber elastomers is recommended. in high and low temperature applications. They show excellent resistance to oxygen and ozone. In addition, they have good resistance to vegetable oils, high aniline index oils, engine and gear oils. They have moderate resistance to swelling in mineral oils and greases, ether-glycol and water-based brake fluids up to 100 ºC and strong swelling in low molecular weight esters and ethers, aromatic and aliphatic hydrocarbons, concentrated acids and bases and steam. We have a special silicone capable of working down to -100 ºC.
Rubber elastomer
Since it contains fluorine in its composition, it presents a superior chemical resistance, being Viton® the best known of them. Fluoroelastomers are the most suitable rubbers for continuous service in a temperature range between 200 ºC and 250 ºC and are also flame retardant. The rubber elastomer recommended for contact with hydrocarbons, mineral oils and greases with additives, fuels and both aliphatic and aromatic hydrocarbons, inorganic acids and bases even at high concentrations.. In peroxide cured formulations, FPM improves its compatibility with traditionally incompatible fluids such as alcohols, hot water, steam and alcohol-containing fuels. They have good resistance to ozone and aging. However, they suffer strong swelling with organophosphates (Pydraul 10E), ammonia, amines, steam, polar solvents (ketones, dioxane, ethyl acetate), as well as in flammable fluids (Skydrol) and brake fluids based on ether-glycol.
Perfluoroelastomer
They are fully fluorinated polymers with elastomeric characteristics and highly recommended for applications with aggressive chemicals and at high temperatures (up to 327 ºC).. They have a almost universal chemical resistance, similar to that of the PTFE. Presentan eigh-temperature thermal stability. They have a excellent steam, ozone and weather resistance. However, they have poor physical properties and limited use in low temperature services. They are attacked by fluorine-containing compounds (refrigerant R11, 12, 113, 114...).
In EPIDOR SRT we have a wide range of O-rings for valves with material formulations for the most demanding working conditions. If you want more information about these materials contact with us and we will study together the most appropriate solution to your problem. Get to know all our engineering solutions in watertightness at our catalog.