Improper design and use of O-rings can accelerate their damage and lead to loss of sealing performance. Experiments show that if the sealing device is designed properly, simply increasing the pressure will not cause O-ring failure. Under high pressure and high temperature operating conditions, the main causes of O-ring failure are permanent deformation of the O-ring material and gap seizing caused by the O-ring being squeezed into the sealing gap, leading to twisting during movement.
The compression set of O-ring materials is temperature-dependent. Leakage will occur when the deformation rate reaches 40% or higher. Therefore, the heat resistance limits for several rubber compounds are: nitrile rubber 70℃, EPDM rubber 100℃, and fluororubber 140℃. Consequently, various countries have established regulations regarding the permanent deformation of O-rings. The dimensional changes of O-rings made of Chinese standard rubber materials at different temperatures are shown in the table.