The Cause of Mechanical Seal Leakage Due to the Medium

(1) After most mechanical seals of submersible sewage pump are disassembled, the auxiliary seals of static ring and moving ring are inelastic, and some of them have rotted, resulting in a large number of leakage of mechanical seals and even the phenomenon of shaft grinding. The corrosion of the static ring and the auxiliary rubber seal of the dynamic ring caused by the weak acid and alkali in the high temperature and sewagecauses leads to overlarge mechanical leakage. The material of the dynamic and static ring rubber seal ring is nitrile-40, which is not resistant to high temperature and acid and alkali. When the sewage is acid and alkaline, it is easy to be corroded.

Countermeasures: for corrosive media, the rubber parts should be fluororubber with high temperature resistance, weak acid resistance and weak alkali resistance.

(2) Mechanical seal leakage caused by solid particle impurities if solid particles enter the seal face, it will scratch or accelerate the wear of the seal face. The accumulation speed of scale and oil on the shaft (sleeve) surface exceeds the wear speed of the friction pair, so that the moving ring cannot compensate the wear displacement. The operation life of hard-to-hard friction pair is longer than that of hard-to-graphite friction pair, because solid particles will insert into the sealing face of the graphite sealing ring.

Countermeasures: the mechanical seal of WC to WC friction pair should be selected where the solid particles are easy to enter.

Specific practical application suggestions:

1. Help users establish appropriate life expectancy and effect expectation, which is also the basis of integrity and long-term cooperation;

2. It is very important to change the user's concept of "replacing machine seal only when it is missing". In general, the overall service life of the machine seal can be expected (for example, one year). If the machine seal has been used beyond the time limit, even if there is no leakage, it is still recommended to replace or check the machine seal when repairing the equipment. And the particularity of working conditions is likely to reduce the expected life of the machine seal or increase the cost of fault shutdown, so timely maintenance is very important.