End face mechanical seal assembly with high temperature secondary seal

A high temperature secondary seal between a rotating seal face adaptor sleeve and a rotating shaft does not consume additional axial space beyond the axial space occupied by the secondary seal. The seal includes a single ring drive collar comprising a plurality of radial directed bolts in tapped holes. As the bolts are tightened they enter a cylindrical cavity in the drive collar and impact therein a sloped surface of a crush ring. The vertical force thereby applied to the crush ring displaces the crush ring axially into a secondary graphite sealing element, thereby crushing the secondary sealing element against the adaptor sleeve and shaft, and forming a seal there between. The crush ring sloped surface can terminate in a vertical face, so that upon sufficient displacement of the crush ring the bolts abut the vertical face and impact the shaft, fixing the drive collar to the shaft.