The Effects Of Mechanical Seal Failure On Centrifugal Pumps

We’ve written a number of posts on our blog about mechanical seal failure and why it happens. But one thing we haven’t really discussed is what happens to a centrifugal pump when a seal fails.

Mechanical seal failure has an effect on many different parts of a pump, including the pump shaft. To find out how seal failure affects the pump shaft, I talked to one of our most experienced service technicians.

1. SLEEVE / SHAFT WEAR
   When mechanical seals fail, they tend to spin on the shaft, or shaft sleeve. Grooves are worn into the metal and require that the shaft or sleeve be replaced. Once they’re worn, they shouldn’t be re-used.
   
   
2. GOUGING, DENTING, SCRATCHING OF SHAFT
   In the case of a catastrophic failure and shattered seal faces, bits of tungsten, or silica carbide can gouge, dent, or scratch the shaft or the sleeve. Sliding a new seal over the damaged shaft surface will ruin the new o-ring on the seal, setting the seal up to fail from the start.
   
   
3. CORROSION OF SEAL SHAFT
   Over the course of a long term seal failure, where the seal is leaking or dripping small amounts of fluid, the shaft can become corroded and weaken.
   
   
4. FLASHING OR ETCHING
   Flashing or etching occurs most often in situations where the fluid is very hot, or in a boiler feed application.
   
   
5. FRETTING
   Fretting is wear caused by movement of the mechanical seal. If the seal faces are damaged, or the seal is improperly installed, a great deal of movement will occur, causing fretting on the shaft.

If a mechanical seal has failed and damaged the pump shaft, it’s best to just replace it. Continuing to use a damaged shaft or sleeve will cause more issues down the road, and will most certainly become a more costly repair.

Mechanical seal failures causing problems beyond just the seal? Ask us about it! We gladly provide technical assistance to business and municipalities in Wisconsin and upper Michigan.