A major problem facing the U.S. Navy is that of brine pump failure on the ships. Faced with this continuous problem, one of the largest shipbuilders in the U.S., Northrop Grumman, decided to conduct a test utilizing the Eddy Pump technology in replacement of the existing brine technology.
The Eddy Pump is not a class of centrifugal pump or a vortex-type pump, but rather an application of the tornado phenomenon, which creates and harnesses a dynamic fluid eddy effect within the pump housing and inlet. A very strong synchronized central column of flow develops from the pump rotor to the pump inlet and creates a low-pressure reverse eddy flow from the pump inlet to the pump discharge. This action enables the pump to achieve significant operational and maintenance performance improvements above and beyond centrifugal and vortex pumps.
Eddy Pumps apply the tornado phenomenon, creating a fluid eddy effect within the pump housing and inlet.
Tests showed that the existing distilling unit brine pump on CVN-68 class ships had high failure rates due mainly to premature motor bearing failure. This was in turn attributed to pump cavitations and related vibration with excessive packing gland leadoff. Based on the current brine pump’s operation at very close to the minimum required net positive suction head (NPSH), which subjects the centrifugal pump to severe cavitations, the need for a solution was of utmost importance.
There was initial concern that the Eddy Pump would have difficulty working in vacuum applications due to low NPSH, but because the Eddy Pump principle of operation does not depend on NPSH, this was not a factor.
Initially, an Eddy Pump was scheduled for a three-to six-month evaluation on the U.S.S. John F. Kennedy (CV-67), utilizing a horizontally oriented pump system with an 8-in. intake and 6-in. discharge. Due to the ship’s scheduling commitments, the pump remained on for more than one year and accumulated more than 3,000 hours of runtime without any problem or failure.
The simplistic design of the Eddy Pumps allows them to operate for years with trouble-free operation and minimum maintenance. They operate without the need for an impeller, but instead use a patented rotor design that can avoid wear longer than impellers. Wearing plates and wear rings are not needed to regulate the efficiency. This is not the case with centrifugal pumps and often results in high maintenance and replacement costs.
To date, Eddy Pumps have been on the U.S.S. Kearsarge for more than 8 years with no problems. Final analysis done by Newport News showed an average lifecycle savings of $3,000,000 per ship by utilizing the Eddy Pump technology versus the existing brine pumps.
Eddy Pumps can pump slurry containing rags, plastic bags, hairballs and other debris. In many cases, the rugged cruciform rotor will break up the debris material. A chopper or a macerator pump is not needed, as the pump is able to move the material through the discharge pipe.