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the failure of mechanical seals there are three main reasons
Feb 09, 2018

(1) sealing surface open


    When repairing a mechanical seal, 85% of the seals fail not to wear out but to leak before they wear out.


    When the sealing surface is opened, the solid particles in the medium enter the sealing surface under the action of liquid pressure. After the sealing surface is closed, these solid particles are embedded in the surface of the soft ring (usually the right ink ring), which effectively becomes a " Wheel "will damage the hard ring surface.


    As the moving ring or rubber ring is fastened to the shaft (sleeve), when the shaft is moving, the moving ring can not fit in time, so that the sealing surface is opened and the sealing surface lags behind and the solid particles enter the sealing surface .


    At the same time there are also solid particles between the shaft (sleeve) and the sliding parts, affecting the sliding of the rubber ring or moving ring (relative to the dynamic sealing point, common faults). In addition, the media will also rub the rubber ring and the shaft (sleeve) to produce crystalline material, there will be a solid material in the spring, will make the sealing surface open. Mechanical seal


(2) overheating


    Because the sealing surface will produce heat, so the rubber ring temperature should be lower than the design specifications. Fluorine rubber and PTFE use temperature of 216 ℃, nitrile rubber temperature of 162 ℃, although they are able to withstand higher temperatures, but the heat generated by the sealing surface is high, so the rubber ring has continued vulcanization The danger of eventually losing its elasticity. (Cold area to consider the cold crisp)


    Between the sealing surface will also cause crystallization of the medium due to heat, such as carbon, resulting in sliding parts are stuck and the sealing surface is condensed. And some polymer due to overheating and coking, some fluids due to overheating and even lost lubrication and other flash fire.


    In addition to overheating can change the condition of the medium, but also exacerbated its corrosion rate. Caused by the deformation of metal parts, alloy surface cracking, and some coating cracks, the design should choose a balanced mechanical seal to reduce the pressure to prevent overheating.


(3) ultra poor


    Correct assembly tolerances are necessary to install a mechanical seal. The shaft (sleeve) must have a suitable surface finish and the correct dimensions, but manufacturers rarely provide tolerance data that is key to installation of. (Rely on experience and common sense)


    Mechanical seal dimensional accuracy and shape tolerance must meet the requirements of the drawings, over-tolerance will lead to seal failure in advance.


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