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PEI’s AVS 4800 Single Stage RO High Pressure Pump Achieves 91% Hydraulic Efficiency

Posted 03/10/08

AVS 4800 on PEI’s large test stand

PEI’s AVS 4800 has achieved a hydraulic test efficiency of 91% during a series of tests conducted in 2007 through January 2008. The AVS 4800 pump’s design point is at a capacity of 5,700 gpm at a total developed head of 1107 ft at 3,600 rpm. The AVS pump line is specifically designed for sea water reverse osmosis desalination service. The pump is intended to operate as a matched set of units with the AT Hydraulic Turbocharger, with both sharing the same US and international patent pending Volute Insert technology, custom hydraulic design, machined impellers, and product lubricated bearings.

Robert Oklejas, Pump Engineering’s President and chief designer of the AVS pump line, explained the significance of these technical features and how each contribute to the AVS’s world best performance. For instance, the Volute Inserts allow both the AT Turbo and AVS pump to be designed and manufactured to specifically match the desalination plant’s conditions. A 5,500 gpm AVS is a different hydraulic design than a 6,000 gpm pump. With the AVS pump, the plant’s duty point and the pump’s BEP (Best Efficiency Point) are the same. The Volute Inserts are replaceable mirror image half volute sections that are designed with Ansys blade Modeler and CFX 5 software for optimized performance. The Volute Inserts are machined on 3-axis CNC milling machines and hand finished to minimize hydraulic friction and turbulence.

The Volute Inserts are replaceable and thus allow a rerating of the pump if changed membrane conditions require a new head and capacity. In this way, a lifetime of energy wasting off design operation is avoided.

Computer designed and manufactured machined impellers are another key to the high efficiency of the AVS. 5-axis CNC machining produces the optimal 3D blade geometry with a precision and surface finish significantly better than even investment casting.

All AVS pump bearings are product lubricated, thereby eliminating the need for oil lubrication and the complexity and expense of an auxiliary lubrication system. The AVS 4800 model tested featured a sea water lubricated Hyper X thrust bearing manufactured by Waukesha Bearing Company. This bearing and the single journal bearing contribute to very low mechanical drag losses and simplicity of design. A single ANSI 5610 mechanical seal operating at pump suction pressure is used for shaft sealing.

PEI’s AVS high pressure pump and the AT Turbocharger clearly create new possibilities for the RO plant designer to minimize capital cost, installation cost, and maintenance cost for large RO desalination plants. However the AVS/AT combination also displays an energy efficiency that is always markedly superior to impulse turbine/multistage pump combinations and as good to often better than isobaric ERD/multistage/booster pump combinations.

Pump Engineering has been a leader in energy recovery devices for desalination and other industries for over 20 years. With PEI devices in operation in more water recovery trains than any other supplier, its low Total Life Cycle Cost approach has proven meaningful for both small and large applications worldwide. For more information contact PEI at: sales@pumpengineering.com or (011) 734-242-1772.