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Three Reasons For Leakage
Apr 23, 2018

1, the sealing surface opens

In the repair of mechanical seals, 85% of seal failures were not caused by wear, but they had leaked before wear.

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

Since the moving ring or the rubber ring is fastened on the shaft (sleeve), when the shaft is tangled, the moving ring cannot be adhered in time, and the sealing surface is opened, and the hysteresis of the sealing surface is closed, so that the solid particles enter the sealing surface. .

At the same time there are solid particles between the shaft (sleeve) and the sliding parts, affecting the sliding of the rubber ring or the moving ring (relative to the dynamic sealing point, common failures). In addition, the medium will also produce crystals in the area where the rubber ring and the shaft (sleeve) are rubbed, and there will also be solid material in the spring, which will cause the sealing surface to open.

2 overheated

Because the seal surface generates heat, the rubber ring should be used at a temperature lower than the design specification. The use temperature of fluororubber and Teflon is 216°C, and the use temperature of NBR is 162°C. Although they all can withstand higher temperatures, the heat generated by the sealing surface is higher, so the rubber ring has to be further vulcanized. The danger is that it eventually loses its elasticity and leaks. (cold area considers cold and crisp)

Between the sealing surfaces, the crystallization of the medium due to heat, such as carbon, causes the sliding parts to stick and the sealing surfaces to condense. Moreover, some polymers are coked by overheating, some fluids lose their lubrication due to overheating, and even flash fires.

Excessive heat can alter the condition of the media and exacerbate its corrosion rate. Causes deformation of metal parts, cracking of alloy surfaces, and cracks in certain platings. The design should use a balanced mechanical seal to reduce the specific pressure to prevent overheating.

3 out of tolerance

Correct assembly tolerances are necessary for the installation of mechanical seals. The shaft (sleeve) must have the right surface finish and the correct dimensions, but manufacturers rarely provide tolerance data. This data is critical to the installation. of. (Rely on experience and common sense)

The dimensional accuracy and geometric tolerance of the mechanical seal must meet the requirements of the drawings. An overshoot will lead to early failure of the seal.

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