Zoeller’s Reversing Grinder Installation at Randall’s Island

Randall’s Island, a popular year-round outdoor destination in New York City, attracts over three million visitors each year. A collection system with numerous small pump stations runs throughout the area for facilities located on the 433-acre site. A few years ago, some submersible pump stations began experiencing frequent clogging problems, requiring emergency service. The park’s service providers were informed of a product that might eliminate their problem.

They were told that Zoeller Company makes a bi-directional submersible grinder pump ranging in size from 2.0 to 7.5 HP (Model 7011). For the past 25 years it has successfully handled problem applications that traditional solids-handling and grinder pumps struggled with. The design incorporates rotating cutter blades that grind axially across a stationary plate. The plate contains a unique pattern of slots and orifices that the sewage passes through as it is being ground up and then pumped out of the basin. Both the cutter and plate are made of 440C stainless steel hardened to a Rockwell HRC 58 or “cutlery” steel, ensuring a long service life. The uniqueness of this design was not only its manner in grinding up solids in the waste stream, but also its ability to change the direction of the rotating blades every time the pump starts a new operating cycle. While the pump is in operation, rotating and grinding in the clock-wise or forward direction, it will stop after emptying the basin. When the basin refills, the pump will start operating again, but it reverses course, rotating and grinding in the counter clock-wise direction. The cutter continues to change direction after each pumping cycle, keeping the cutting surfaces clean. Keeping these surfaces clean eliminates the potential for a clog to develop. As an added bonus, this system also had the ability to be retrofitted onto the existing rail system and operate from the existing control panel already at the Randall’s Island facility.

In July of 2015 two 5 HP grinder pumps and a reversing box were purchased. When the system was installed and started up in September, Zoeller received positive feedback on their operation with no clogging occurring during the first few months of operation. While that was good news, success couldn’t be claimed until the pumps went through a full year’s cycle of operation.

After a year of operation, Zoeller inquired into the status of the application to see how the pumps had been performing. While it was reported that the original Randall Island’s pumps were clogging on a regular basis, not once had the Zoeller Engineered Products’ reversing grinder pumps failed to perform even after fourteen months of operation. In the wake of the success of the new Randall’s Island system, two additional sets of ZEP pumps and reversing boxes were ordered, retrofitting two more stations at the site. As anticipated, another user experienced the satisfaction of Zoeller’s dependable reversing grinder pump.