The mechanism of blister formation on carbon-graphite mechanical seal facesw((c))

Blister formation on carbon-graphite mechanical seal faces most commonly oc curs in oil and hydrocarbon service, with higher viscosity oils, and with s top-start cycling. Blisters form unexpectedly, often with catastrophic resu lts. In this study: an experimental apparatus that closely simulates field conditions was used to form blisters on five different grades of carbon-gra phite seal faces. The tests showed that blisters form at the instant of ini tial shaft rotation. Significantly more blisters form as the viscosity of t he oil between the seal faces increases when chilled. The blisters are loca ted randomly around the seal face and not in regular patterns. The authors conclude that blister formation is a mechanical process through which a sha llow subsurface crack is formed by shear forces acting at the carbon-graphi te seal face.