Modifications can be made to many older pumps to improve on their original design. Pump rebuilders with experienced engineering staffs can provide these modifications and upgrades to substantially extend mean time between repair (MTBR) and increase pump longevity. In the following case history, an ash handling water pump that had been experiencing a short operational history was removed from service on an emergency basis because of catastrophic bearing failure caused by poor lubrication.
This pump was shipped to the service center where it was disassembled and inspected. It was observed that the bearings had failed and the rotor had moved axially toward the non-drive end, allowing the second stage impeller to contact the pump casing (see Figure 1).
Excessive wear was noted at all running clearances. Discussions with the plant subsequently revealed that these pumps have an average MTBR of 18 months. Excess running clearances accompanied by rotor axial movement have resulted in similar failures on sister pumps. Continue reading