The facility replaced old grinder pumps with stainless steel shredder pumps, which have needed no maintenance in almost two years.

Americans consume approximately 3 billion pounds of cereal each year. The production of this vast amount of cereal requires efficient and reliable equipment for every step of the process. This is why one cereal processing plant that had been experiencing frequent pump problems decided to revamp its wastewater lift station with new stainless steel shredder pumps.

The cereal plant, located in the southern U.S., has had a long-standing relationship with Georgia-based Goforth Williamson, Inc. (GWI), a pump repair and field services provider. Having consistently provided the cereal processing plant with pump repair and on-site support, the plant solicited help from GWI to find a solution to a frequent, costly repair problem.

The wastewater lift station at the cereal processing plant had been using two grinder pumps within a duplex system. Designed for constant duty, the pumps worked in tandem. One pump would operate while the other acted as a backup, and the pumps would switch operation as needed. Unfortunately, both pumps needed to be pulled for repair at different times each year. This short time between repairs resulted in an annual cost of $7,000 that continued for several years.

Every repair involved the same set of issues:

  • Seal failure. The wastewater lift station, which has a submergence depth of about 18 feet, was using these grinder pumps to process wastewater that contained bits and pieces of cereal as well as sugars. The grinder pumps were experiencing excessive seal failure that required them to be sent to GWI's service center.
  • Impeller degradation. While at the GWI service center, the inspectors saw signs of degradation of the impellers and other internal metals that had been exposed to the wastewater. The wastewater contained varying amounts of sugar that caused the pH of the pumped liquid to range from 2.5 to 8.0. The grinder pumps had cast iron components, which are more susceptible to degradation when exposed to acidic or corrosive liquids. The plant's wastewater had been slowly damaging the cast iron impellers.

After years of constant repair, the cereal processing plant worked with GWI to find a pumping solution better suited to their wastewater application. They determined that replacing the old pumps with two stainless steel shredder pumps would drastically improve their operations. The features of the new pumps were ideal for this particular application:

  • Manufactured from 316 stainless steel, the pump elements exposed to the liquid are able to withstand the wastewater's wide range of pH, eliminating the corrosive effect to the wear and wet parts. Because the impeller, wear plate, oil housing, pump housing and inner pump top are all made of 316 stainless steel, this pump would increase mean time between repairs.
  • Specifically designed for industrial shredding applications, these pumps are engineered to use a tungsten carbide impeller. This cutting impeller cuts against a spiral-shaped diffuser plate to continuously rip apart solids with 360-degree shredding actioin.\
    Manufactured with non-clog, single-vane impellers designed for high volume and lift performance, the pumps are rated to cut and pass solids up to 3.5 inches in size, while pumping up to 700 gallons per minute.
  • The pumps offer three-seal motor protection.
    • The motor is protected with an oil-lubricated double seal design.
    • The double mechanical seals are comprised of a lower seal made of silicon carbide/silicon carbide and upper seal faces made of carbon/ceramic.
    • An additional lip seal is installed above the impeller to help prevent abrasives from entering into the seal chamber.
  • The motor overload device protects the motor from thermal and amperage overloads. Incorporating winding protection and National Electrical Manufacturers Association (NEMA) Class F motor insulation, the motor can withstand temperatures up to 230 F. An automatic switch turns the pump motor off if the temperature or amp draw gets too high. When the motor cools, the switch automatically resets, and the pump will begin operating again.

The cereal processing plant purchased two 10-horsepower submersible shredder pumps to be installed in the wastewater lift station. GWI advised the plant to order the submersible pumps with 4-inch American National Standards Institute (ANSI) flanges so the pumps could be installed with custom-built slide rails. The pumps were installed in December 2013 and have not been pulled for maintenance since the installation.