Spotting extrusion damage is actually quite easy. Visual indicators include patterns of small nibbles on the downstream edge of an O-ring, producing a surface that appears chipped. More severe cases of extrusion may be present when the surface of an O-ring appears as though it has been peeled away. Extrusion into both the top and bottom of the groove is typically indicative of O-ring gland overfill.
Extrusion in radial seals can be prevented by adding a plastic or metal backup ring or by decreasing the gland clearance gap. The option of a properly-sized, harder O-ring material may also be beneficial. During application design, evaluate the approximate pressure rating for the seal. Additionally, confirm the elastomer compatibility with the temperature range and fluids used in the application.
Worth noting: static face seals often have no extrusion gap, so these applications can withstand much higher pressures than radial seals. Absence of this gap significantly reduces the risk of extrusion.