DNV GL has launched a new joint development project (JDP) to test the influence of Environmentally Acceptable Lubricants (EALs) on failures in stern tube bearings.
DNV GL in cooperation with marine insurers The Swedish Club, Norwegian Hull Club, Gard and Skuld, will oversee detailed laboratory testing of EALs by Leonardo Testing Services at the University of Sheffield, UK.
There has been an increasing failure of stern tube bearings, which coincides with the uptake of EALs and new propulsion system designs including single stern tube bearing installations and larger, heavier propellers operating at lower RPMs. The JDP will therefore look to understand these failures by conducting studies that compare the lubrication performance of EALs with traditional mineral oils in stern tubes.
Hydrodynamic oil film formation, oil film thickness under varying loads and temperatures and potential shear thinning effects at high shear rates will be tested. According to DNV GL, state-of-the-art non-invasive ulstrasonic techniques developed by the Univeristy of Southampton will be used to examine the behaviour of the lubricant film in real time.
Øystein Åsheim Alnes, Principal Engineer at DNV GL says: “With this new study we hope to gain a better understanding of factors influencing the lubrication performance of EALs.”
“DNV GL supports solutions that can reduce the environmental impact of the maritime industry. Our aim in this study is to undertake a first-hand assessment of the performance of EALs in order to guide the further development of the DNV GL Rules,” says Alnes.
Testing will begin this year and the first phase is expected to be completed in the first quarter of 2018. The results will be published later in the year.
Images: Above – Propeller shaft system, Right – Oil sample bottles.