An increasing number of liner shipping companies are favouring seawater lubricated propeller shaft bearings over oil lubricated versions, for both newbuilds and retrofits, says Canada’s Thordon Bearings. This is because of environmental considerations and the need to cut operating costs.
Recent orders include UK-based Lomar Shipping’s decision in November to opt for Thordon’s COMPAC bearing solution for two 2,700 teu newbuilds that are being built by China’s Guangzhou Wenchong Shipyard Co. Previously, in late 2015, Thordon Bearings signed a milestone agreement to supply its COMPAC system to two 3,600 teu Jones Act box ships under construction by Philly Shipyard in the USA for Matson Navigation.
A driver of this new business has been the United States Environmental Protection Agency’s ruling in December 2013 that vessels over 24m must adopt environmentally acceptable lubricants in all oil-to-sea interfaces before their next drydocking. It recommended that seawater lubricated bearings be used in propeller shaft lines in newly constructed vessels.
However, there have been challenges in getting shipyards to use seawater lubricated propeller shaft systems.
Thordon Bearings director of marketing and customer services Craig Carter said: “When shipowners build a ship, they typically write a specification and ask shipyards to quote. Due to unfamiliarity with seawater lubricated propeller shaft systems, many shipyards do not promote them. In fact, many shipyards have discouraged them even when shipowners specifically ask for them. Another issue is that when the shipowner receives a quote from the shipyard, the yard typically charges a premium, compared to an oil lubricated system.”
Frequent demand from shipowners, however, is beginning to bring about a change of thought. “Chinese yards, in particular, have learned that building a ship with water lubricated propeller shaft bearings actually takes less time and has fewer components than a ship with an oil lubricated system, so they are financially better off,” said Mr Carter.
A major development in seawater lubricated bearing technology, and one that many consider to be the main attraction for container shipowners, is the change in classification rules for seawater lubricated propeller shafts, providing extended shaft withdrawals on par with oil systems.
DNV GL, Lloyds Register, China Classification Society and Bureau Veritas have now modified rules for seawater lubricated propeller shaft systems, which means that the shaft does not have to be withdrawn for inspection for 15 years or longer from the date of build, if certain monitoring condition criteria are met. This is equal to an oil lubricated propeller shaft and removes a major obstacle that shipowners met with water-based propeller shaft bearing systems.