Analysis on the causes of failure of static seal mechanical seals

　There are four main forms of general mechanical seal failure, namely corrosion, thermal damage, wear and tear and failure caused by installation and operation. The pump was disassembled without scratches and wear on the seal face, so physical damage to the seal face could be ruled out as a cause. Considering that there are more crystalline materials and rusty skin in the seal cavity, the self-priming pump, combined with the many manifestations of mechanical seal failure, initially determined that the easy crystallization and corrosiveness of the transported medium is the main cause of seal failure.

Improvement measures

1, change the structure of the elastic element: the elastic element from the spring to the bellows, the bellows is both the elastic element and the dynamic ring of the auxiliary seal, eliminating the original dynamic ring and the sleeve between the O-ring, only the dynamic ring seat at the end of a gasket to seal the material there, so as to solve the contradiction between the O-ring seal and compensation, and the original quasi-static seal to a complete static seal, so that the reliability of the seal is improved. The bellows also eliminates the transmission pin of the spring mechanical seal and the mating surface between the moving ring and the moving ring seat, avoiding the failure of the moving ring action caused by the deposition of solid particles and further improving the overall performance of the seal. The bellows provides both elastic compensation and torque, and the exhaust gas absorption device has better follow-through and compensation capability.

2. Static ring compensation instead of dynamic ring compensation: The mass of the dynamic ring part in the seal assembly is much larger than that of the static ring part, so the rotational momentum in operation is also large. After changing to static ring compensation, the rotational momentum is reduced and the stability and reliability of the whole seal assembly is improved.

3、Increase the gap between dynamic ring and sleeve: Increase the gap can avoid the deposition of crystalline matter and rusty skin, increase the inner diameter of dynamic ring or reduce the inner diameter of sleeve under the premise of ensuring the end surface pressure. According to the recommendation of the relevant information, the clearance is increased from 0.38mm to 0.5mm.

4、Appropriately increase the aperture of the flushing line: for the actual situation of more crystalline and rusty skin, increase the flushing volume can effectively solve the deposition of solid particles, so the original flushing line aperture must be increased from 12.7mm to 19.05mm.