Marine owners and operators need to seize every possible advantage nowadays in a regulatory environment that poses tougher restrictions on pollutants and an economy that demands reducing costs to stay competitive. In recent years, marine lubricants have been developed to help operators meet the challenges of today’s shipboard operating environment.
Petroleum-based fluids and lubricants used in shipboard equipment are developed to be environmentally friendly and safe, while delivering specified properties of power and lubricity. Flexible hoses, stern tube seals, controllable-pitch propellers and other hydraulic power units aboard ships are susceptible to rupture, damage and ultimately leakage. The risk of machine oils being discharged into waterways by a marine vessel is significant and has caused lubricant manufacturers to produce lubricants that are inherently biodegradable, minimally harmful to marine life, yet able to maintain anti-corrosive as well as lubricating properties.
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Courtesy Shell |
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Shell’s Marine and Power Innovation Centre in Hamburg, Germany, where researchers developed Alexia S4, a product that significantly lowers consumption of lubricating oil in marine diesels. |
Jeff Sherman, commercial marine sales manager for MTU Inc., explained that lubricant selection, combined with filtration and purification, is crucial in maintaining the lubricating properties required by today’s marine diesels.
Marine diesel engines undergo a variety of stresses. The source of these stresses include heat, insolubles that find their way into the lubricant, acidity and ambient humidity. A carefully developed marine lubricant may combat such stresses and result in more favorable engine performance in many different ways.
Low-sulfur and ultra-low sulfur requirements have created new opportunities for lubricant manufacturers. Sulfur in the fuel serves to lubricate various components. Lower sulfur requirements subtract from that lubricity and can result in premature component wear if lubricants are not carefully selected and monitored.
“Our engines are designed to run on 15 ppm of sulfur, which is the lowest of ultra-low sulfur,” said Sherman. Sometimes there may be some thinning of the sulfur content of the fuel, bringing the sulfur content below 15 ppm, resulting in a significant loss of lubricity. “We’ve seen component failure as a result,” he said, noting the importance of measuring fuel to make sure that there is no thinning and that the sulfur ppm count is sufficient.
According to Buck Bradberry, marine account manager of North America lubricants for Chevron, lubricant manufacturers have produced products with sufficient alkalinity to combat the formation of sulfuric acid, which can form when sulfur interacts with water vapor in the combustion process. The acidic stresses can cause premature erosion and wear of cylinder components, but alkyd additives in lubricants are designed to counter that formation.
With the advent of ultra-low sulfur fuels, explained Bradberry, sulfuric acid formation is less prevalent, yet the alkyds are still in the lubricant and have nothing to react to and neutralize. This has resulted in the alkyds “plating out,” or forming ash deposits, often in the engine exhaust, posing a new problem for operators. This is particularly the case for smaller operators who aren’t as aware of the proper lubricant to be used with low-sulfur applications. Many deep-draft marine operators, says Bradberry, who burn Bunker C in slow-speed diesels have a lower alkyd lubricant specified.
ExxonMobil’s Mobilgard 560 VS lubricant was tested on the Hapag-Lloyd containership Colombo Express with low-sulfur fuels. The new characteristics of this product allow it to be used in engines where the fuel’s sulfur content varies. In the case of Colombo Express, the vessel burned a heavy fuel oil with less than 1 percent sulfur content. The improved lubricity of Mobilgard 560 VS reduced mechanical wear and enabled a longer time between overhauls.
Another ExxonMobil product, Mobilgard 570, is designed for engines burning low-sulfur heavy marine fuels. An additional benefit of the product is that it reduces the “oil-feed rate,” the rate at which the lubricant is burned or consumed. When tested on a Danaos Shipping containership, the product was able to extend the piston overhaul interval from 16,000 to 42,575 hours.
Shell Marine Products achieved a similar success story through a trial of the Shell Alexia S4 lubricant aboard vessels operated by the German-flagged Oldendorff Carriers. The lubricants were tested when one of the company’s vessels exhibited signs of excessive oil consumption. The oil-feed rate was reduced using the new product. It was found that the lubricant consumption by the engine was reduced by 33 percent, significantly impacting the company’s return on investment.
According to Bradberry, many engine manufacturers and designers changed component design to enable a smaller lubricant film between piston rings and cylinder liners, thereby reducing oil consumption. Lubricant manufacturers are also changing the chemistry and characteristics of their lubricants to improve performance in two-stroke, medium-speed diesel engines that burn diesel fuel.
Bradberry says that oil consumption on two-strokes is reduced in part due to multi-grade viscosities of the lubricants. He explained that this development originated with railroad locomotives, where it was discovered that lubricants designed to operate in environments that demand multiple viscosities were ideal in reducing the feed rate.
“Lubricant manufacturers put viscosity modifiers in their products and this has helped quite a bit,” he said. The viscosity modifiers provided greater adhesion of the lubricant to the cylinder walls, thereby reducing its propensity to be burned or consumed.
He cited Chevron studies on medium-speed engines showing that its lubricants helped reduce oil consumption by 15 percent through the use of multi-grade lubricants.
Lubricant qualities are even more important where lower speeds make the propulsion components within the engine more prone to failure because of frequent throttle cycling to lower speeds to achieve lower fuel consumption. “If you have a boat that operates on a hard throttle all the time — let’s say a tug that’s pushing all the way down the East Coast with a consistent rpm load, that oil may last longer than a ship that is throttling up and down all day long and idling a lot,” said Sherman, of MTU. “It really comes down to operation and load profile.”
Good lubrication translates into better performance and better efficiency, he explained. “The quality of oil and the different classes of oil has much to do with it. There’s Type I and Type II oil and then you have synthetic oils.”
According to Sherman, a Type I will not last as long as say a Type II or a synthetic lubricant. Synthetics are more expensive but are known to last longer. But he says that today’s Type II lubricants are being developed with better characteristics and qualities that allow them to retain their lubricating properties longer, almost as long as some synthetics.
“We do not require synthetic. We can get the same output with a Type II oil as we can with a synthetic,” Sherman said. “That’s a savings to the customer because synthetics are an expensive oil.”
Engine manufacturers are required to meet environmental standards but customers expect a certain life expectancy of the engines they buy. “It is critical that the engine manufacturers and lubricant manufacturers work together in developing their products,” said Sherman. “What may be good for them (lubricant manufacturers) may not be good for the engine.”
Sherman feels that there has been great collaboration over the past three to five years, resulting in a good complement of engines and lubricants. “I think the critical component is that we do communicate with each other,” he said. “That is absolutely necessary on both sides of the fence.”
Ben Bryant, the North American marine market manager for Klüber Lubrication, a supplier of specialty lubricants whose North American headquarters is in Londonderry, N.H., believes there’s another key benefit to modern lubrication product development. According to Bryant, the next big environmental challenge for marine operators is to reduce the stream of oil-based lubricants entering oceans, bays, harbors and inland waters from standard operational practices. Bryant cited a study that says between 1.2 million and 7.6 million gallons of lubricants are discharged into commercial harbors each year through stern-tube leakages, and another 8.5 million gallons of lubricant are discharged through other on-deck and below-deck machine elements.
“In the draft version of the 2013 Vessel General Permit (VGP), the U.S. EPA has proposed rules that begin to address this environmental problem,” Bryant said. “In the draft, the EPA lists several applications that will require EALs (environmentally acceptable lubricants) on all new vessels over 79 feet and on all existing vessels where technically feasible. On or before March 15, 2013, the EPA will publish the final VGP and the rules will go into effect next December. Vessel operators have either begun the transition to environmentally acceptable lubricants or are waiting for the final rules before taking action.”
Bryant said that Klüber’s products are designed to meet the EPA’s final rule and to exceed the performance characteristics of currently available lubricants. “Our lubricant development process is focused on selecting the best biodegradable base oils, matching them with additives that provide superior performance, and working with OEMs to test our products,” he said.
“Some lubricant manufactures are developing cylinder oils that match up to the low sulfur content fuels required to operate in ECA zones,” explained Bryant. “In the three-to-five-year time frame (the required time of phase-in of the requirements), a potentially large opportunity for vessels is to take advantage of energy savings accrued from the use of high performance lubricants in shipboard gear boxes,” said Bryant.
Bryant said that research in other non-marine industrial applications indicates that a 1 to 2 percent reduction in energy usage can be documented by switching to a better lubricant. “Theoretically, these same energy savings are available on board vessels,” he said. However it is difficult to measure due to variations in the load on the system from one voyage to another caused by weather, speed, cargo loads, etc.
Bryant believes the same efficiencies gained in applications on land can be achieved aboard vessels and even a 1 percent energy reduction would directly relate to fuel cost savings. Switching to high efficiency gear lubricants, he said, could be a component of a ship’s energy efficiency management plan.
Panolin America Inc. manufactures environmentally friendly lubricants and power fluids for stern-tube seals, thrusters and compressors, as well as grease products for cabling and sliding parts. “These products follow the United States Environmental Protection Agency bio-preferred criteria,” said Jared Mikacich, sales and marketing director for Panolin America. “The steps we take are critical in meeting these specifications, and equally important, exceed performance requirements from our customers.” According to Mikacich, the company uses unique esters to achieve their environmentally friendly qualities.
Chevron offers a line of Clarity Marine Lubricants that have anti-corrosive properties and are easily filtered and separated from water, while still achieving adequate properties to be used as a lubricant or power fluid.
Mikacich explained that Panolin’s products are environmentally friendly but, like Chevron’s Clarity lubricants, they do not sacrifice performance by being environmentally safe if discharged. He says they tolerate high pressures and are compatible with most sealing surfaces, and maintain excellent corrosion inhibition.
