Thordon Bearings COMPAC seawater-lubricated bearing system
Peer-reviewed analysis by Thordon Bearings into the hydrodynamic lubrication effectivity of a ship’s propeller shaft bearing has discovered that the usage of seawater-lubricated elastomeric polymer bearings reduces gas consumption.
The environmental and monetary advantages of adopting a seawater-lubricated propeller shaft system are properly documented, however that is the primary affirmation that the association reduces hydrodynamic resistance sufficient to enhance gas consumption, in comparison with a traditional oil-lubricated bearing association.
NEW RESEARCH METHODOLOGY
The ground-breaking analysis is predicated on new methodology for calculating the efficiency of seawater-lubricated bearings, which, till now, has been primarily based on a decades-old principle developed for oil-lubricated propeller shaft bearings.
“Classic rigid surface bearing theory is valid and commonly used for oil-lubricated metal bearings. 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,” Thordon Bearings’ chief analysis engineer, Dr. Gary Ren, says in a peer-reviewed paper published in the July edition of the Elsevier journal Tribology International.
“We believe Dr. Ren’s method is more accurate, because it takes into account the characteristics of seawater as a lubricant, the polymer materials used, bearing pressures, viscosity, friction and so on,” stated Elena Corin, senior supervisor, particular marine tasks, Thordon Bearings. “This is the first time anyone has investigated whether there are differences in friction coefficient between the two types of bearings. And there are!”
Corin added that the brand new methodology offers “strong evidence” to quantitatively help the advantages of a Thordon COMPAC system.
“By applying the results, we were able to determine the minimum required shaft speed for hydrodynamic lubrication efficiency, the coefficient of friction as well as the water film thickness at any given load and shaft speed,” she stated.“Test results confirmed that fuel losses due to the friction coefficient [hydrodynamic resistance] of an oil-lubricated propeller shaft bearing system can be reduced by as much as 85% by using seawater-lubricated polymer bearings.”
COMPARISON
Thordon Bearings used the methodology to check the gas consumption of a Panamax containership and an Aframax tanker working a 640 mm (25.2 inch) diameter oil-lubricated propeller shaft bearing versus the identical ship working an open COMPAC seawater-lubricated bearing system.
Each vessel was assumed to run on VLSFO (very low sulfur gas oil) at a world common worth of $890/tonne working for 70% of the time.
The outcomes confirmed that gas losses as a result of friction coefficient (hydrodynamic resistance) of an oil-lubricated propeller shaft bearing system might be lowered by as a lot as 85%.
“Fuel costs will depend on the operational profile of the vessel, but we conservatively estimate annual savings of at least $10,000 per vessel,” stated Corin. “This is in addition to the other life cycle cost savings associated with a Thordon seawater-lubricated bearing system.”
“Reducing friction coefficient is another reason why a seawater-lubricated propeller shaft bearing system pays dividends for ship owners and operators, commercially and environmentally,” stated Craig Carter, Thordon Bearings’ vice chairman enterprise improvement. “Reducing friction coefficient is another reason why a seawater-lubricated propeller shaft bearing system pays dividends for ship owners and operators, commercially and environmentally. When you consider the operational cost of running an oil-lubricated propeller shaft over 25-years, a seawater-lubricated shaft line pales by comparison.”
CII IMPLICATIONS
Thordon Bearings is now finishing up analysis to evaluate the carbon emissions discount attributes of vessels utilizing a seawater-lubricated system to assist shipowners meet CII (Carbon Intensity Indicator) necessities.
From January 1, 2023, shipowners can be required to doc their Attained Annual CII and confirm it towards the Required Annual CII to find out their vessels’ operational carbon depth score. Savings in gas consumption and subsequent discount of CO2 emissions are the main focus of the CII measure.
