Written by: Ron White & Ben Roberson, HydroAire Inc.
A “temporary” repair results in five years of service.
Five years ago, an engineered pump service center in the Midwest received a call from a large municipal sanitary district. One of the company’s four submersible pumps had tripped the overloads. This 890-rpm unit operated on variable frequency drives that adjusted the motor speed to match the fluid inflow. Once it had been reset, the 290-horsepower, 42-inch diameter axial flow pump exhibited significant vibration before failing. The pump was removed and sent to the service center where it was cleaned, disassembled and inspected by a team of skilled professionals dedicated to repairing submersible pumps.
The initial inspection revealed that a large chunk of concrete debris from nearby sewer construction caused the submersible pump to fail. The inspection also showed that the pump had several problems:
- A section of the trailing edge of one of the impeller vanes was broken.
- The rotating ring was missing.
- The impeller hub and lower mechanical seal had cracked and caused damage to the shaft keyway.
When the municipality inquired about replacement parts from the OEM, delivery was estimated at a 12- to 14-week turnaround time on a new impeller from Europe. The municipality could not afford to be without the pump for an extended period of time. Having a great deal of experience with submersible pumps, the dedicated submersible repair division proposed a temporary solution to get the pump repaired and back into service until the municipality could obtain a new impeller from the OEM.