Benefits of seawater-lubricated shaft bearings highlighted

Thordon Bearings recently published a study highlighting the commercial and environmental benefits of seawater-lubricated propeller shaft bearing arrangements.

This study indicated that shipowners can make substantial operational savings by switching from an oil lubricated shaft. The study, presented at SMM 2018, was carried out in response to the increase in oil and oil-based environmentally acceptable lubricant (EAL) lubricated stern tube bearing failures, which are placing an additional and unnecessary financial burden on shipowners.

Despite the introduction of legislation to reduce shipping’s impact on the oceans, together with shipowners’ ever-present need to reduce opex, the majority of commercial deepsea vessels continue to use a system that is increasing risk and is costly to operate, Thordon said.

“It is quite staggering that over 95% of all new commercial ships continue to be built with oil lubricated propeller shafts – a system that is not only operationally expensive but environmentally questionable,” said Craig Carter, Thordon Bearing’s director of marketing and customer service.

“’ Our Future, Our Ocean’ paper presents the case for water lubrication to shipowners and shipbuilders as a commercially and technically viable way of increasing profits while achieving corporate sustainability goals,” he added.

The 14-page report explains that while the low capex of an oil-lubricated system is an obvious attraction, any financial advantage is completely lost once the vessel enters the water. This is due to the costs associated with purchasing lubricating oils, regular maintenance and unscheduled drydockings required to repair or replace faulty shaft seals, Thordon claimed.

While emergency seal repairs alone can cost between $150,000 to $300,000, excluding drydocking costs, the paper pointed out that the constant topping up of an oil lubricated system, combined with the regularity of aft seal failure, can cost shipowners in excess of $6.5 bill over a 25-year period.

In another move, Thordon Bearings is offering its COMPAC seawater lubricated propeller shaft bearing system with a lifetime bearing wear life guarantee, instead of the original 15-year wear life guarantee.

Performance data

This extended warranty is based on an extensive study of the performance data of the 550-plus COMPAC shaft bearings in operation on commercial vessels, dating back more than 25 years.

When the bearing operates in conjunction with Thordon’s water quality package (that removes abrasives), ThorShield anti­corrosion shaft coating, shaft liners and SeaThigor forward seal, bearing wear is negligible, providing optimum through life performance, the company claimed.

Thordon’s Global Service & Support (GSS) division has also added propeller shaft alignment services to its global technical support portfolio.

This new service completes the company’s offering, providing shipowners with a one-stop-shop maintenance, installation and commissioning solution for Thordon’s entire product portfolio.

For vessels experiencing vibration problems or other alignment issues, Thordon’s GSS teams can be deployed to provide onsite shaft line investigation and measurement services to determine the load on the bearings. This includes in depth modelling of the shaft line, analysis of the stresses placed on the bearings and a complete review of the bearing height using strain gauges in order to optimise load distribution.

Several representative marketing agreements have also been signed recently, including coverage in Spain and the Baltic and Caspian seas.



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