High-pressure solutions for reverse osmosis applications

In the early phases of the Ashkelon project Sulzer Pumps committed to develop a pump range designed to optimize cost and dedicated to high-pressure feed to seawater reverse osmosis (SWRO) applications for medium and large plants. Sulzer Pumps Engineering looked at both the application itself and what the future trends in market would be. The approach was to build a range of pumps able to match the following main characteristics.

The design work was executed in close  cooperation with some of the most established engineering contractors in the field of SWRO plant construction. These new developments contributed to the development of plant designs and to the improvement of efficiency, reliability and availability of the high pressure (HP) feed pumps.Potentially, there are two design concepts applicable to the multistage pumps used for high pressure feed duties in SWRO applications.

Sirst, the volute type axially split casing design with a single pressure boundary, and, second, the diffuser type segmental ring casing design with a multiple pressure boundary. In the initial development phase both designs were considered to develop the multistage pumps needed for the above-mentioned range of operating conditions in high pressure feed services. Finally, the decision was made to focus the engineering efforts on the volute type axially split construction, as it was the most appropriate solution.

In a second step, the current diffuser type segmental ring casing pump range was extended to cover feed flows up to 900 m3/h to provide a pre-engineered alternative for medium sized installations.Opposed impellers for axial hydraulic balance of the rotor and center balance bushing to provide rotor-dynamic stability and high degree of dampening of critical speeds, even when the parts are worn.