Design of bearing housing and bearing fit
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Gentlemen, I’ve recently run into a troublesome issue: in the workshop, there’s an imported multi-stage pump whose thrust bearing mechanical seal keeps breaking down. Upon disassembly and inspection, it was found that the sealing surface on the bearing housing cover was severely worn. Moreover, the structure of this bearing housing is different from that of all pumps I’ve encountered before; there is no interference fit between the bearing and the bearing housing, and it’s only a small anti-rotation pin that prevents the outer ring of the bearing from rotating due to radial forces. Over time, this pin falls out, which leads to further wear of the sealing surface on the bearing housing cover, increases axial movement, and ultimately results in damage to the seal. It’s really frustrating. Do any of you have any good suggestions? I would appreciate your advice. Thank you!
Large axial play is a problem with the balance disc; under normal operating conditions, the thrust bearing should not be subjected to axial forces, except during startup or when the operating conditions change. In other words, in theory, under normal operating conditions it’s fine to remove the thrust bearing. The axial force is mainly balanced by the hydrostatic balance of the balance disc. It is recommended to check the balance disc mechanism.
It is possible that a problem with the balance disc has caused an excessive unbalanced axial force, leading to deflection toward the inlet side and resulting in over-compression of the mechanical seal on the thrust side. The fit between the outer ring of the thrust bearing and the bearing housing should be an interference fit; wear on the flange edge may occur if the fit clearance is too large.
Based on the poster’s description, the issue lies in anti-re resale measures; if a way is found to prevent those measures from being disabled, then all problems will be solved
1. Try to restore the anti-rotation feature; if that’s not possible, the radial fit issue can be resolved by plating or turning the lower sleeve! 2. The axial clearance between the gland and the bearing can be ensured by replacing the gland or by turning the sealing surface of the gland! It refers to cutting hair!
There are no detailed drawings; it’s foreign-made equipment. The schematic diagrams are available above, and I didn’t take pictures of the actual product – it should be easy to understand
But I always feel that this design isn’t reliable – a single pin is too weak
The bearing sleeve and bearing housing are not designed with an interference fit; it’s the first time I’ve encountered such a design. There is no issue with shaft play, and I personally don’t think the problem lies with the balance disk. In the last two instances, seal leakage occurred after two months of continuous operation following maintenance, and upon disassembly, I found the condition I described