(1), The secret cover open
In the repair of mechanical seals, 85% of the seal failure is not caused by wear, but before the wear has been leaked.
When the sealing face is opened, the solid particles in the medium enter the sealing surface under the action of the liquid pressure, the sealing surface is closed, these solid particles are embedded in the soft ring (usually the right ink ring) surface, this actually becomes a "grinding wheel" will damage the hard ring surface.
As the movable ring or rubber ring is fastened on the shaft (sleeve), when the shaft is strung, the movable ring can not fit in time, and the closed cover is opened, and the sealing surface lags behind, so that the solid particles enter the sealing surface. There is also a solid particle between the shaft (sleeve) and the sliding part, which affects the sliding of the rubber ring or the movable ring (relative dynamic sealing point, common fault).
In addition, the media will also be in the rubber ring and shaft (sleeve) friction parts produced crystals, in the spring will also have solid material, will make the secret cover open.
(2), overheating Because the sealing surface will produce heat, so the rubber ring use temperature should be lower than the design specifications. Fluorine rubber and PTFE use temperature is 216 ℃, NBR Rubber's use temperature is 162 ℃, although they can withstand the high temperature, but because the sealing surface produces the heat to be high, therefore the rubber circle has the continuing vulcanization the danger, finally loses the elasticity to leak.
(Cold zone consider cold crisp) The sealing surface is also due to heat caused by the crystallization of the medium, such as carbon, resulting in sliding parts are stuck and the sealing surface is condensed.
And some polymers are overheating and coking, some fluids due to overheating and loss of lubrication, and even flash fire. Overheating, in addition to changing the condition of the medium, also increases its corrosion rate.
The deformation of the metal parts, the cracking of the alloy surface, as well as some of the coating cracks, the design should be a balanced mechanical seal to reduce the specific pressure to prevent overheating.
(3), ultra-poor The correct assembly tolerances are necessary for the installation of mechanical seals, the shaft (bushings) must have proper surface roughness and the correct size, but the manufacturer rarely provides tolerance data, which is critical to the installation.
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