Submersible Sump Pump Saves $23,000 Annually at Water Reclamation Facility

When a pump repeatedly fails, the root cause must be determined. Sometimes the solution can be as easy as understanding that the pump is not right for the specific application.

"Some applications require special pumping equipment," said John Forgette, outside sales engineer at Cortech Engineering, which provides engineering and pump support services to many industries throughout California and Nevada. Cortech Engineering was contacted in 2013 by a California municipal water district that has an on-site water reclamation facility. Refineries rely on the district to send up to 5 million gallons of reclaimed water per day to be further treated and used for boiler feed and cooling tower applications. The district had previously worked with Cortech Engineering and decided to contact the company to discuss a solution that would help its water reclamation facility save $23,000 a year in replacement pumps. The water reclamation facility had been experiencing frequent failures of its submersible sump pumps, which operated in microfiltration backwash waste pits and ran continuous-duty 24 hours a day, seven days a week. The slurry pumped was a byproduct of the treatment process and contained abrasive solids that included the washed-over sand and coal particulate from the filtration process. The solids had been causing excessive wear to the submersible sump pumps in the pits. The district's maintenance team was tired of replacing the submersible pumps every six months, so the group asked Forgette to recommend submersible pumping equipment that would be better-suited for its specific application. Forgette considered the maintenance team's major concerns:

• Endurance for continuous duty. Each microfiltration backwash waste pit utilizes a single submersible pump operating 24/7 continuous duty, so the water reclamation facility needed a high-endurance submersible pump that could withstand the continuous running condition.
• Resistance to abrasive solids. The water reclamation facility needed submersible pumps that could pump the particulate without quickly wearing out. Frequent pump failure from abrasion and erosion had been causing unwanted maintenance and downtime costs.
• Pump reliability. The previous pumps had failed because they were not designed for the long run times or for effective handling of abrasive slurry, so the reclamation facility needed submersible pumps that would perform reliably for the specific application.

Forgette worked to find the right equipment for the water reclamation facility's microfiltration backwash waste pits. The facility selected a submersible slurry pump with 28 percent high-chrome iron components (600 Brinell, 57 Rockwell C) and other features, including a hard metal agitator that keeps solids suspended in liquid in order to improve the pump's operation. The selected pump also included a replaceable hard metal wear plate on the suction side that minimizes loss of pump performance as a result of erosion as well as a hard metal semi-open impeller that handles abrasive solids with concentrations as high as 70 percent by weight. The pump also featured a stainless steel shaft and shaft sleeve that reduces shaft wear from abrasive materials and corrosive liquids. The pump volutes are cast from hardened ductile iron (300 Brinell hardness) and are twice as abrasion-resistant as standard ductile iron. The slurry pump model is protected by double silicon-carbide mechanical seals that are housed in a separate oil-filled seal chamber. The heavy-duty lip seal offers additional protection for the mechanical seals. The motor is protected with Class R motor insulation, built-in amperage (full-load amps, or FLA) and temperature-overload protection. As a top-discharge pump, it is cooled by the pumped liquid. It can pump sump pits down to within inches of the bottom. Forgette reviewed the submersible slurry pump's features with the maintenance team members at the water reclamation facility. They agreed with the recommendation and opted to include a seal oil leak detector used in conjunction with an alarm circuit in the pump control panel. The water reclamation facility purchased one top-discharge submersible pump to test its performance in a microfiltration backwash waste pit. The pump was installed in September 2013 "and has been running great ever since," Forgette said. "Having that agitator has really helped because it pulls those solids up in the pit instead of letting the solids settle around the pump." The result has been "reduced downtime and labor expenditures," he added, noting that the water reclamation facility is planning to install a second submersible pump in another waste pit in a different section of the plant. A major benefit has been that "improved pump reliability is having a significant impact on their maintenance budget," Forgette said.