Thordon: Water-Lubricated Propeller Shaft Bearings Reduce Fuel Consumption

Thordon Bearings has released results of a study that examined the hydrodynamic lubrication efficiency of a vessel’s propeller shaft bearing system. Simply put, the study found that the use of seawater-lubricated elastomeric polymer bearings—as opposed to oil-lubricated bearings—reduces fuel consumption.

Prior to the study, calculating the performance of seawater-lubricated bearings was based on the old methodology developed for oil-lubricated propeller shaft bearings.

“Classic rigid surface bearing theory is valid and commonly used for oil-lubricated metal bearings,” Thordon Bearings Chief Research Engineer Gary Ren said in the study. “However, two major factors of seawater-lubricated bearings, namely low lubricant viscosity and deformability [of the polymer bearing surface], make the application of rigid surface bearing calculations susceptible.”

Elana Corin, senior manager of special marine projects for Thordon, said Ren’s methodology is more accurate because it looks closely at the lubricant qualities of water compared to oil.

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“This is the first time anyone has investigated whether there are differences in friction coefficient between the two types of bearings,” Corin said.

The test found that fuel losses due to that friction coefficient of an oil-lubricated propeller shaft bearing system can be reduced by as much as 85 percent with seawater-lubricated polymer bearings.

The project looked specifically at a blue-water applications, with Panamax containerships and Aframax tankers both studied. The study found that a similar ship would likely see an annual savings of $10,000 with the use of a seawater-lubricated propeller shaft bearing system, in addition to reducing emissions.

And while the Thordon study focused on the blue-water industry, using Thordon’s COMPAC bearings, the principle applies to brown-water systems as well. Thordon offers a line of elastomeric polymer tailshaft bearings for towboats and tugboats under the RiverTough brand.