Lubrication and protection of ship engines became much more complex after implementation of IMO 2020 fuel regulations, making testing ever more important in choosing the correct cylinder oils, speakers said during an online webinar.
Marine lubrication has been more complex than ever before, Caroline Huot, senior vice president of ship management for Delta Corp. Shipping, said during “Marine lubrication for ULSFO, VLSFO and safeguarding engines,” a Riviera Maritime Media webinar held June 7. “The complexity was already there, with the introduction of new engines, a few years ago, but it has been increased by the fact that matching the fuel type and the cylinder oil has not been sufficient to obtain optimal results,” she said. “Complexity in the lubrication and the handling of the cylinder oil became the rule of the game.”
IMO 2020 required ships operating in most ocean waters to be equipped with exhaust scrubbers that capture sulfur dioxide or to use fuel with no more than 0.5% sulfur – much less than the previous limit of 3.5%. Operators of ships without scrubbers could choose from three categories of fuel – very-low-sulfur fuel oil, distillates such as vacuum gasoil or liquid natural gas.
Cylinder oils that lubricate large marine engines are mixed with fuel, so the different categories of fuel exert different formulation requirements for oils. One of the main differences is the base number of the oil formulation, which represents its ability to neutralize acids formed in the cylinder environment. Very-low-sulfur fuel oil requires a base number between 20 and 30, while marine diesel oil or gas oil require base number of only 12-15 and LNG just 4-7. Scrubber-equipped vessels that continue to use high- or intermediate-sulfur fuel oils require cylinder oils with base number of 30-55.
Huot said main ship engines can be damaged in several ways that relate to cylinder oils, the most common being cylinder liner polishing and scuffing, adhesive wear on the cylinder liner, and lacquering and increased lube oil consumption when operating on low-sulfur marine gas oil. Wax particles can also block filters, pipes and other equipment at low temperature when operating on distillates.
She recalled that original equipment manufacturers issued a number of service letters to recommend switching to low-sulfur cylinder oil – in particular products with base number of 40 – and outlined how to operate and how to manage feed rates. “However, it means attention needed to be given to cylinder oil management like never before,” she said. “Cylinder oil is definitely not a commodity, and cylinder oil management is an integral part of maintenance plans for an owner that is trying to minimize the cost of maintenance. Following OEM’s service letters is key.”
She explained that operators following this guidance had to gradually decrease feed rate in order to obtain the optimal rates recommended by the OEM. “You couldn’t just change over to the new low-sulfur cylinder oil and drastically decrease feed rate right away because these would definitely result in a possibility of cold corrosion and insufficient neutralization of corrosive acids,” Huot added. The adjustment instead needed to be gradual change, and was best done in conjunction with analysis to corroborate whether progress the chemistry of the fuel-lubricant mix was going in the right direction.
Very regular, systematic drain oil analysis to check iron and BN, feed-rate adjustments when required in order to data mine what is the optimal feed rate are also important, she added. Also visual inspections, piston ring coating thickness measurement and visual piston underside inspections were important. “After a few months, the first issues we had seen coming started disappearing and we found a balance of optimal feed rates and use between the high and low BN cylinder oil, which was controlled regularly through drain oil analysis and regular laboratory analysis,” she recalled.
Paul Parkinson, Veritas Petroleum Services’ group business development manager for oil condition monitoring, recounted that independent insurer The Swedish Club found that $647,920 was the average cost of a main engine claim in 2018. The insurer found that ship main engine damage claims totaled $131 million, representing 34% of all claims that year. “IMO 2020 and COVID-19 will potentially increase this in 2021 and beyond, I’m sure.”
He advised three actions to help avoid running into main engine damage situations.
“First of all, select the correct cylinder oil in relation to your fuel choice, and if you’re changing supplier, compatibilities to these can help this transition and minimize any cost that you might incur,” Parkinson said.
He also recommended performing regular sampling analysis of cylinder oil and fuel. “A regular scrape-down analysis is a great tool to identify the cylinder condition,” he said. The test can identify ferrous iron concentration in the scrape down oil, which provides an indication of an engine’s liner wear rate caused by abrasive wear
“An onboard test kit for measuring iron and base number is also useful,” Parkinson said. “Take some samples and send them to your lab for a detailed scrape down analysis, so you can see some detailed analysis of cylinder oil.”
Don Gregory, technology and innovation director with Gulf Oil Marine, noted that that it can be quite difficult to report engine problems such as cylinder liner scuffing. “Ships are quite remote, the information isn’t always perfect and photographs aren’t of the highest quality,” he noted. “Getting samples and analyzing them are great help in trying to understand what the problems are.”
According to Gregory, Gulf Oil Marine’s experience has shown that cylinder base oil numbers of 140 have a great effect at cleaning out cylinder liners that are in poor condition. “On the other hand, with 2020 fuels, this is a bit of a problem because we are now introducing a very high ash content, overbased cylinder oil, which isn’t required for neutralization purposes in order to act as a detergent,” he explained. “That’s one of the ongoing challenges we are facing in the industry, in terms of how do we develop the solutions for tomorrow.”
Gregory also talked about the efforts of the International Council on Combustion Engine’s Marine Lubricants working group. According to IMAC’s website, the group, which meets twice a year, includes experts from all relevant disciplines – ship operators, engine and equipment manufacturers, oil and additive suppliers, classification societies and scientific institutions. The group works to define industry positions for the use and maintenance of lubricating oils in different types of ship engines.
He said the Marine Lubricants working group is currently providing support and direction for diesel ship engine lubricants and accepting user feedback questionnaires on engine problems. The group is preparing to issue an information paper for dissemination to users such as ship’s engineers in 2022.
Gregory noted a future challenge surrounds the goal of zero fossil carbon emissions. This could be through the use of biofuels, hydrogen, ammonia, methane and other alternative fuels. “All these fuels will come with their challenges for the cylinder oil,” he added. “What the industry faces is that the frequency of challenges is increasing, while the time to resolve those challenges and design new cylinder oils is definitely decreasing.”