Drawing on OEM reports and its own engine performance tests, Castrol Marine has strengthened its conviction that optimum performance, when slow steaming, can only be achieved by having a range of cylinde r oils available for the customer.
The company says its research and development, OEM recommendations, market trends, legislation and, most importantly, customer feedback have combined in developing its latest cylinder lubricant offer, based on the realities of slow steaming, fuel sulphur content and low feed-rates.
Its investigations show that each vessel should use a cylinder lubricant based on its predominant operating conditions, and while 40 BN cylinder oil suits vessels predominantly operating in ECAs, cylinder oils of 70 BN and above are better suited to those vessels regularly slow steaming, to ensure piston ring packs and liners remain in excellent condition.
“The idea of a single, mid range cylinder oil solution for all vessels as sulphur limits are reduced may be seductive, but our field evaluation shows this does not offer the best margin of safety,” says Paul Harrold, Castrol Technology Manager Marine & Energy Lubricants.
“Slow steaming has complicated traditional assumptions concerning engine performance because marine engines are not designed to operate below 85% power for prolonged periods. At lower loads, the cylinder oil’s feed rate is reduced, reducing the available BN to neutralise acids and reducing the oil film thickness. This can mean lubricants degrade, increasing the potential for acidic corrosion and increased wear rates.
“Lower engine operating temperatures caused by slow steaming further increase the risk of cold corrosion,” says Mr Harrold. For owners, this could mean unscheduled and costly maintenance. Severe cases may require liner and ring reconditioning or replacement, Castrol warns. “Replacing liners on a 14-cylinder engine could cost over US$1 million,” Mr Harrold points out.
“Higher BN lubricants provide greater neutralisation and hence better corrosion protection across the fuel sulphur range while slow steaming.”
OEMs confirm there is no need to change the cylinder lubricant if operating in an ECA for around 10 – 14 days. Castrol’s experience has shown that using a high BN product for even longer is often acceptable when operating in an ECA, especially when slow steaming.
Fears that high BN cylinder oils may lead to deposits and bore polishing may be unfounded, the company adds. “Reducing speed by only 3 knots will have the same impact in ash reduction as changing from a high to a low BN lubricant. When you think that operations in the ECA involve port visits combined with the current climate of slow steaming, most vessels will naturally reduce their speed,” says Mr Harrold.
On this basis, Castrol is confident that owners specifying higher BN cylinder oils do not necessarily have to change lubricant when visiting an ECA.
“We are not suggesting that a ship has to carry a range of products,” says Mr Harrold. “In fact, the majority will carry only one, depending on their engine and voyage operating pattern. We have a 40 BN for prolonged operations in ECA, while our existing 70 BN cylinder oil has proven itself in intermittent ECA operation. For the most severe applications of optimised feed rates and slow steaming we would consider recommending 80 BN cylinder oil for many customers.
“Our position is that only by having a comprehensive range of cylinder lubricants to choose from can vessel operators maximise machinery performance and provide the highest margin of safety. Castrol will add an 80 BN option to its already extensive range of cylinder lubricants.”