Top Causes of Mechanical Seal Failure in Centrifugal Pumps
Dry running, misalignment and chemical incompatibility as leading causes of premature seal failure.
A mechanical seal keeps the pumped liquid inside a centrifugal pump. Most seals do not wear out naturally; they fail because of a cause that can be found and fixed. Replacing the seal without fixing the cause means the next one fails too.
Running dry
The seal faces rely on a thin film of liquid for lubrication. If the pump runs without liquid, the faces overheat and crack within a short time. Causes include a closed suction valve, an empty tank or an air lock.
Wrong installation
Incorrect spring compression or setting length, scratched faces, a damaged O-ring or a dirty shaft sleeve give early leakage. Handle the faces carefully and follow the maker's installation dimensions.
Shaft movement and vibration
Excess shaft deflection, worn bearings, misalignment or cavitation make the seal faces open and close, and cause leakage and wear. Check shaft runout and bearing condition.
Dirty or abrasive liquid
Solids can enter between the faces and wear them. A flush line, a cyclone separator or a seal arrangement designed for solids helps. Crystallising or sticky products can also hang the seal up.
Heat and wrong materials
A seal that is run above its temperature limit, or made of materials not suited to the liquid, will harden, swell or corrode. Check the face and elastomer materials against the liquid and temperature.
Poor operating conditions
Running the pump far from its best efficiency point causes vibration and recirculation. Frequent dry starts and thermal shock also shorten the life of the seal.
What to do
When a seal fails, examine the faces and O-rings, since the wear pattern often shows the cause. Check the pump for the causes above before fitting a new seal.
Key Takeaways
- Dry running and poor installation are common causes.
- Check shaft runout, bearings and alignment.
- Match seal materials to the liquid and temperature.
This article is general guidance. For a recommendation for your own application, contact our engineering team. Seals and sealing solutions →