RAD-AX® Submersible Pumps Solve Wipes Problem For Wastewater System

David Vauthrin

FoxRock Properties owns and operates two massive office and medical complexes in Norwell, MA. The first of the neighboring properties is Longwater Place, a 27,000 square foot office building, part of a larger 26-acre campus including 84,000 square feet of corporate offices and a 160,000 square-foot wellness center. Longwater Place incorporates a full cafeteria, and fitness center, featuring a gymnasium with squash courts and locker/shower facilities.

The adjoining property is South Shore Medical Center. The 85,000 square-foot facility comprises 100 medical examination rooms, 70 medical offices, and a complete range of diagnostic equipment.

With the size of these commercial buildings, you can easily imagine the wastewater handling challenges faced by property management. There are 30 bathrooms and 64 toilets throughout the complex.

The Process

Flow content from the office and medical complex includes sanitary waste, wipes, and feminine hygiene products flushed by staff, patients, and visitors. All of it travels through the sewer lines of both properties and is funneled into an outside 10,000 gallon over- flow tank. The wastewater is then pumped through a 4-inch PVC discharge pipe over one-eighth of a mile from the tank into the municipal sewer system. Two solids-handling submersible pumps are at the heart of the system.

Although not required by local regulations, FoxRock Properties maintains this pumping system to ensure that discharges to the municipal sewer system can be handled effectively by the local treatment facilities.

The Challenge

Traditionally, municipal systems employ numerous smaller capacity lift stations to move raw sewage and wastewater from individual sanitary drain lines to main sewers leading to treatment plant intakes. Small lift station pumps are particularly susceptible to clogging since their solids handling capability is limited. These units typically allow passage of soft solids up to one-half the suction inlet. They do not easily handle long, stringy materials like wipes, which tend to wrap and bind impellers. The resulting pump clog causes an initial pump failure and quite possibly more consequential motor and system damage.

The property manager for FoxRock, Dan Snyder explains, “Given the buildings’ populations, professional range of clients and types of services provided, it is expected that we would see more than our fair share of flushables”. He went on, “In the past we experienced frequent failures as wipes blocked screens protecting the pumps and wrapped around impellers, clogging the volute, and eventually burning out the pump’s submersible motors.” Even with a back-up pump in place, the service interruptions and maintenance costs became unacceptable.” The average pump service life was under 1.5 years.

After one of the 460-volt submersible pumps failed again, Snyder decided to ask the water and waste equipment specialists at Williamson New England Electric Motor and Pump Company to take a look at the problem and recommend a solution to the pump failures.

The Solution

Jae Wilson, Service Manager at Williamson New England Electric Motor and Pump Company reviewed the system and its hydraulic requirements including the difficult-to-pump wastewater content. Although there are numerous solids-handling pumps available, none presented the perfect solution. Research indicated that the heavy wipe content would still tend to wrap and clog pumps with traditional non-clog impellers. The resulting failure meant lifting the pump, disassembling and manually clearing the blockage, and possibly replacing the motor.

Jae consulted with one of his premier pump suppliers, BJM Pumps, which manufactures a wide range of non-clog submersible shredder pumps for industrial and municipal services. The timing could not be better. BJM Pumps offered Jae an opportunity to install one of the first of a new line of shredder pumps, the SKG Series with RAD-AX® technology. The Radial Shredding is achieved by a rotating cutter bar with serrated edges, which traps and shreds solids against the sharp grooves of the radial cutting ring. Wipes and other fibrous debris are efficiently ripped apart. The complimentary Axial Cutting utilizes dual cutting elements operating in tandem to multiply the shearing action. As the material exits the radial shredding area, the axial cutting components shear any remaining pieces using multiple cutting bars. The impeller design expedites the flow and hydraulic performance, preventing wrapping and clogging.

RAD-AX® shredding elements that are cast in hardened 440C Stainless Steel (Rockwell hardness above 55C) for maximum service life. The patent-pending RAD-AX® design is available with 2, 3, or 5HP high torque 4-pole motors. These pumps are perfect for smaller waste water stations and perfect for the FoxRock sump application.

The required pump was immediately available and quickly installed. One important advantage was immediately noticeable. Most non-clogs, including the second wastewater sump on the FoxRock property, need to be surrounded by a screen. The solids and debris that get caught in that screen, need to be routinely cleared by hand. The BJM Pumps SKG does not require a screen. A post installation inspection revealed no debris in the sump.

Dan Snyder, “So far I am very happy with the pump. It was installed in July, 2014 and continues to operate without clogging.”

It is impossible to prevent non-flushable materials from entering the wastewater system but at least FoxRock Properties now has the optimum pump in-place to minimize the possibility of clogging. It should also improve the downstream conditions since any solids pumped from the property into the municipal system can be easily handled.

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