Because they clog pumps, non-dispersible wipes have become a source of anguish for many maintenance teams. When pumps that run in critical applications become clogged, the cost to repair or replace those pumps escalates.
These excessive maintenance expenses have been shouldered by many hospitals across the U.S. that have experienced a rapid increase in non-dispersible materials entering their sewage systems.
A nationally recognized, not-for-profit hospital serving eastern Los Angeles and western San Bernardino counties contacted Cortech Engineering in April 2014, determined to address a persistent clogging problem to save on maintenance costs.
Pomona Valley Hospital Medical Center (PVHMC), which is staffed by about 800 physicians and twice as many nurses, is a 437-bed hospital that relies on seven sewage ejection pits to collect waste from the hospital complex. These sewage ejection pits are responsible for pumping waste material out of the buildings and into the municipal sewer system.
Like many other hospitals across the U.S., PVHMC was having problems with disposable wipes. The pumps operating in the facility's sewage ejection pits were consistently becoming clogged with wipes and other materials not designed to be flushed through a sewage system.
Between 2008 and 2014, the hospital's sewage ejection pumps needed to be rebuilt and replaced several times.
"Clogs happen at all times of the year—they don't care whether it's Thanksgiving, Christmas or New Year's Eve. When the pumps get clogged, the maintenance team has to act quickly to keep the system working," said Karen Deshler, outside sales engineer for Cortech Engineering. "When the pumps become clogged, the hospital has to bring in extra maintenance staff and incur higher expenses during off-shifts and holidays. They were spending between $4,500 and $8,500 each time they had to bring in a super-sucker vacuum truck to remove the solids from the sewage ejection pits. Over time, and with repeated incidents, this became quite costly."
Looking for a Solution
Peter Kersten, stationary engineer for PVHMC, began researching grinder and shredder pumps that were available on the market and decided on a submersible shredder pump designed to shred almost everything—from rubber chickens to running shoes. He presented the pump to his bosses and explained how a submersible shredder would meet their critical requirements:
- The pumps needed to be able to shred the disposable wipes and rags that were pushed into the sewage ejection pits. The sewage ejection pits needed to stay clear of fibrous, floating debris to prevent clogs and avoid emergency situations.
- The pumps needed to be able to operate reliably to avoid extra maintenance expenses.
The selected submersible shredder pump can handle up to 3.5-inch solids at 570 gallons per minute with a maximum of 59 feet of head.
Engineered to shred solids, the pump uses a cutting impeller with a tungsten carbide tip to continuously rip apart solids against a tooth-edged, spiral-shaped diffuser plate. With 360-degree shredding action and non-clog, single-vane impellers, the pump can shred the disposable wipes and rags that are pushed through the sewage ejection pits.
The pump is constructed of hardened cast iron to withstand rough handling and a 304 stainless steel motor housing, which offers abrasion-resistance that is superior to aluminum motor housings.
The pump motor is protected with double mechanical seals, which 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 prevent unwanted materials from entering the seal chamber.
Incorporating winding protection and National Electrical Manufacturers Association Class F motor insulation, the pump can withstand motor temperatures up to 230 F. An automatic switch turns the pump motor off if the temperature and/or amp draw gets too high. When the motor cools, the switch is designed to automatically reset, and the pump will once again begin operating.
The pump is also equipped with a seal moisture detection system, which features a sensor probe inside the oil chamber that can provide an early warning to protect the pump motor. When the seal failure circuit, or moisture detection circuit, is properly connected to a control panel, it informs the pump operator that moisture is within the oil chamber. This early warning can allow the operator to schedule pump inspection and repair.
Once the PVHMC decision makers were on board with the selection, two of the submersible shredder pumps were installed in a duplex arrangement inside the 16-foot-deep sewage ejection pit. During installation, under the direction of Cortech Service Manager Mark Fox, Cortech's on-site technicians installed a lifting chain, electrical wiring to a 15-amp breaker for the duplex control panel and the seal moisture-detection relay, and new stainless steel check valves.
"The lifting chain makes it easier for us to hoist the pumps for inspection and maintenance," Kersten said. "The … control panel alerts the staff in case there is a problem, which will help to prevent a burnout. The stainless steel check valves are an added bonus. Cortech recommended the new valves for increased reliability because they will last much longer than the previous cast-iron valves."
With 15 months of successful operation, the submersible shredding pumps are successfully handling the disposable wipes and keeping the 16-foot-deep sewage ejection pit operating smoothly.
"The maintenance staff appreciates the decrease in calls for middle-of-the-night and holiday emergencies, and those managing the maintenance budget are happy to save money they'd been spending on the vacuum truck," Deshler said.
Kersten added, "Last Christmas was the first one I've had off in over three years. No more calls at 2 a.m. to unclog a pump."
The hospital is in the process of purchasing four more submersible shredder pumps for use in two other sewer ejector pits.