One of the most common causes of pump failure is the mechanical seal. There’s many reasons why the mechanical seal could stop sealing, and some typical ones to look out for are shown here.
The seal failure could have started right back when the pump was specified. It’s important to make sure that the seal is capable of normal operating conditions as well as any non-standard processes it will likely be put through (for example, cleaning in place). Additionally, if the pump itself is not operating within the correct system requirements (flow and pressure), it may cavitate, causing overheating of the fluid in the pump bowl and therefore overheating of the seal.
To install a seal properly is a delicate task. The faces are very flat, so even a small amount of oil or dirt can stop them aligning when they’re fitted, let alone pounding it on to the shaft with a hammer. Also, if the pump is imbalanced or misaligned it will cause it to vibrate, wearing away the seal.
Allowing the pump to run dry will often do considerable damage to a pump in a very short space of time. Other common user errors are contamination of the pumped fluid and changes to the system without considering for the effect on the pump itself.