Open loop water lubricated propeller bearings use (sea)water as cooling medium. Depending on the location, the (sea)water will contain a varying number and sizes of solid particles. These particles can over time cause increased bearing and shaft wear, resulting in reduced bearing wear-life.

The solution is to filtrate the (sea)water before it is flushed into the stern tube and over the bearings. Filtrating the water flow by means of regular filter units will rapidly fill up the filter cartridges and is not a time and cost-effective method of removing particles in an open-loop system. To allow effective particle separation and continuous drain overboard, Norden Marine Bearings have developed a range of hydro cyclones fit for the purpose.