Foreign materials in sewage system led the maintenance team to look for a new equipment option.
by Keith Grgurich & Gary Brown
March 27, 2018

We have all seen it in movies—prison inmates sneaking cigarettes and other contraband from one person to another while guards are not looking. While these scenes from cinema may be highly dramatized, the reality is that goods do get smuggled throughout prisons and correctional facilities.

Correctional Facility

One correctional facility in the Great Plains region had to deal with the very real consequences of smugglers’ tape being flushed down toilets.

While there was great effort made to restrict the flow of contraband, this correctional facility struggled to keep unwanted materials from entering the sewage system. Tape, pieces of cloth and other evidence of contraband smuggling were being flushed through the septic system and made their way into a wastewater sump outside of the correctional facility.

The wastewater sump had relied on two grinder pumps in a duplex arrangement to transport the raw sewage from the correctional facility through the sewer system to the local municipal wastewater treatment plant. The problem was that the smugglers’ tape, cloth remnants and other debris had been frequently clogging the grinder pumps.

To alleviate the excessive clogging, the in-house maintenance team at the correctional facility installed catch baskets on the in-flow pipes. These baskets, which were designed with spikes to catch the large pieces of tape and garbage, had to be manually cleaned out three times each week. This was an absolute nightmare for the in-house maintenance staff.

The staff talked with their plumbers and together they decided to look for different styles of pumps that could reliably handle the wastewater without clogging. They discovered submersible shredder pumps and selected one for the following reasons:

The main pumps are engineered to shred solids. They use a cutting impeller design with a tungsten carbide tip to continuously rip solids against a tooth-edged, spiral-shaped cover plate. With 360-degree shredding action and non-clog, two vane impellers, the pumps can shred the tape and other fibrous materials that were being flushed through the correctional facility’s sewage system.

Proven to handle solids up to 3.5 inches in size, the new equipment could pump wastewater at 570 gallons per minute with a maximum of 54 feet of head.

With a motor housing manufactured from 304 stainless steel, the pump is more resistant to corrosion and lasts longer than pumps with cast iron, steel or aluminum motor housings.

The submersible shredder pump is constructed using a hardened ductile iron impeller and suction cover that can withstand pumping solids-laden wastewater—unlike pumps with standard cast iron or plastic components.

The pump’s motor is protected by double mechanical seals and an additional lip seal. In the double mechanical seal design, the lower seal faces are made of silicon carbide/silicon carbide and the upper seal uses cooler running carbon/ceramic. An additional lip seal is installed above the impeller to help prevent unwanted materials from entering the mechanical seal chamber.

The pump also uses motor overload protection and (NEMA) Class F motor insulation. If the motor temperature or amp draw becomes too high, the motor overload switch “opens” and turns the pump motor off. The switch automatically resets when the motor cools, and the pump resumes its operation.

The correctional facility purchased two submersible shredder pumps in addition to slide rail assemblies. The slide rail assemblies were installed to make sure the in-house maintenance team could easily pull the pumps for future inspection and maintenance as needed.

The slide rail assemblies and pumps were installed into the correctional facility’s wastewater sump in June 2015 and have been running well since their installation. There have been no clogging problems, and the in-house maintenance team was able to remove the catch baskets at the in-flow pipes.

When you have a pump that is clogging frequently, you may not have the right pump for your specific application. Frequent clogging can cause headaches and waste precious maintenance dollars. On the other hand, when your pumps are working the way they are supposed to, it frees up your maintenance team to focus on other demands throughout your facility.