Desalinated: Sealing technology in reverse osmosis processes

Seawater desalination plants are already ensuring a sustainable supply of drinking water to many countries today.

In the last few years it was possible to considerably reduce the energy expenditure for the osmosis process. This opens new perspectives for the new construction of such major water technology projects. The requirements towards pumps and their shaft seals along the reverse osmosis process chain vary greatly.

The seawater is drawn in by tubular casing pumps or large submersible motor pumps, then added to the filter systems by booster pumps. The purified water is then pressed through several multistage high pressure pumps into the actual reverse osmosis system. The separated brine is returned to the ocean, the procured drinking water is pumped into tanks for remineralization. Additional pumps are used in energy recovery.

The high to extremely high salt content of seawater and the separated brine and high pressures up to 60 bar (870 PSI) require a technically sound configuration of seal and materials.

The preferred seals are EagleBurgmann SH(V), Cartex and H75 mechanical seals. Structural materials of choice are often Hastelloy® and Superduplex due to their resistance.

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