Weighing the ups & downs of pump repair & replacement
Sometimes it makes sense to repair a pump, and sometimes it makes sense to replace a pump. End users typically do not know which choice is the best until the pump has been pulled out of service, disassembled and thoroughly inspected.
Pump repairs typically include changing out parts, but many times replacement parts cannot be obtained in a timely manner. Situations when delivery times are critical can impact the end users’ decision to repair or replace a pump. Such was the case with one company that provided maintenance services for an airport lift station.
To Replace or Not to Replace
Goforth Williamson Inc. (GWI) provides pumps, pump repair and field services to industrial and municipal markets in the southern U.S. Over the past few years, GWI has completed several pump repairs for a company specializing in building maintenance services.
This facility maintenance company supports a major Atlanta-based airline by performing maintenance services for the airline’s hangar. Not only does the facility maintenance group clean 6,000 aircraft per month; it also is responsible for maintaining the lift station located inside the hangar.
In August 2015, the chopper pump operating in the hangar’s wastewater sump failed. The facility maintenance group sprang into action, pulled the pump out of the sump, and sent it to the GWI pump repair center for inspection. Inspection revealed the chopper pump needed a new impeller, a new cutter bar and a rewind on the motor.
The manufacturer estimated that delivery of repair parts would take four to six weeks, which was too much downtime for the lift station. There was no back-up sump pump, so the facility maintenance group had to temporarily reroute the flow.
Determined to provide a solution for this problem, the hangar’s GWI support representative contacted the facility maintenance group to offer another option. The group was open to replacing the chopper pump, so he suggested BJM Pumps’ line of submersible shredder pumps. He then contacted Steve Mosley, an applications engineer for BJM Pumps, to discuss a particular model of shredder pump that would be ideal for the lift station application.
Selecting the Correct Pump
There were three critical points for pump selection.
The first was how the pump could shred solids in the wastewater sewage. The lift station collected raw sewage from the airport hangar. This raw sewage coming out of the planes and from the hangar’s wastewater contained an excessive amount of “flushable” wipes and rags. The submersible pump would have to shred those solids and operate without clogging.
The second was the pump’s reliability, as the lift station was designed with a simplex system; meaning only one submersible pump operated in the hangar’s wastewater sump. It was important to select a reliable submersible shredder pump to reduce maintenance and avoid downtime.
Lastly, the timeliness of delivery was also considered. The submersible shredder pump would need to be delivered as soon as possible so the facility maintenance group could install a permanent solution into the hangar’s lift station.
After reviewing the pump curve and the system requirements, it was determined the best pump for the job was the BJM SKG37C-460 submersible shredder sump.
This submersible shredder pump is designed with dual shredding RAD-AX technology, which would enable it to shred “flushable” wipes and other solids that saturate the sewage coming into the hangar’s wastewater lift station. The patent-pending design uses radial and axial shredding components to tear through solids. A rotating cutter bar with serrated edges traps and shreds solids against the sharp grooves of a radial cutting ring while multiple axial cutting bars shred any leftover material exiting the radial cutters.
All the shredding components of the pump are manufactured in hardened 440C stainless steel, which met the durability requirements the facility maintenance group sought.
Additionally, the pump relies on a high-torque, four-pole motor to ensure difficult solids are handled effectively. The hydraulics of this pump matched the hydraulics of the original chopper pump, so it met head and flow requirements of up to 42 ft of head and a maximum of 410 gal per minute.
Utilizing a two-vane chrome iron impeller, the pump effectively passes larger solids. The two-vane design also incorporates pump-out vanes on its rear shroud to protect the mechanical seal from solids build-up. The hardened impeller is resistant to wear for longer service life.
Protected by double mechanical seals, the motor has an oil-lubricated double seal design with an upper seal made of silicon carbide/carbon and a lower seal made of silicon carbide. An additional lip seal is installed above the impeller to prevent sewage from entering the seal chamber.
The shredder pump is manufactured with a corrosion-resistant stainless steel motor housing. Class F motor insulation and a built-in motor thermal switch provide winding protection. If amp draw or temperature get too high, an automatic switch turns off the pump motor. The switch automatically resets when the motor cools, and the pump resumes operation.
It also comes with a heavy-duty SOOW power cable and cable entry sealing system. An FKM compression fitting with a stainless steel gland nut holds and seals the cable, and power leads are individually isolated and potted to prevent wicking. In the event moisture enters the mechanical seal oil chamber, an early seal fail warning is sent through the Seal Minder Moisture Detection system.
Once the pump was selected, the regional manager for BJM Pumps, informed the team the submersible shredder pump could be delivered in just two weeks’ time. The airline promptly ordered the submersible shredder pump along with a discharge flange adaptor. The 3-in. ANSI adaptor flange allowed the facility maintenance group to attach the pump to the existing guide rail system.
The BJM Pumps team helped ease the process of selecting a new pump by being quick to respond, helping to determine the best pumping equipment for the application, and delivering the pump quickly. Installation of the pump in September 2016 went smoothly, and it has been operating well for the lift station since.