Seal Failure For Three Main Reasons

(1), key cover open
Repair mechanical seal, 85% seal failure is not caused by wear, but had been leaked before the wear.
When the seal is opened, of solid particles in a liquid medium pressure into the sealing surfaces, sealing surface after closure, these solid particles embedded in the soft ring (usually right Mexican rings) on the surface, it's actually become a "wheel" can damage the hard ring surface.
Because of the ring or a rubber ring is fastened on the shaft (axle), when axis series,, ring not fitting in time and cause the seal to open and delayed closing of the sealing surface, solid particles into the sealing surface.
And shaft (axle) and sliding exist between parts of solid particles affect the rubber ring or rings sliding (dynamic seal, common faults). In addition, the media is in the rubber ring and shaft (axle) friction produced crystals, will also have solid material at the springs will cause the seal to open.
(2), heat
Heat seal face produced, so the rubber ring temperature should be below the design specifications. The temperature for Viton and Teflon 216 c, NBR temperature 162 ℃, although they can withstand high temperatures, but due to the heat of the sealing surface is high, so there is continued risk of sulfide rubber ring, eventually loses its elasticity and leaks.
(3), the variance
Correct Assembly tolerances, are very necessary for installing mechanical seals, shaft (axle) must have a suitable surface roughness and the right size, but manufacturing tolerances for very few of those data, the data is critical to install.