Immersion in water adversely affects many elastomers by inducing considerable compound swell. As increased swell means increased o-ring volume and friction, excessive water swell precludes the use of a number of elastomers in dynamic (moving) situations.
As water is converted to steam, o-ring elastomers are exposed to the degrading effects of heat, in addition to water swell. If heat ranges are exceeded, o-ring materials may assume the condition of a sponge, soaking up gases and fluids, leading to a partial or total loss of sealing properties.
Silicone, Ethylene Propylene, AFLAS®, and Hydrogenated Nitrile, for example, are good performers in water and steam. Perfluoroelastomers are excellent performers in both water and steam, especially at elevated temperatures.