A particular problem with low sulphur residual fuels is the increased severity of the viscosity-breaking process used by petroleum refiners. The blending process can cause severe instability problems which may not be apparent immediately, but which can cause severe problems with asphaltenic sludge in tanks, filters and from the purifier, says Jonas Östlund, product marketing manager, marine chemicals, Wilhelmsen Ships Service.
Quality problems when using distillate fuels are fundamentally different from those of residual fuels and focus around lubricity, storage stability and microbial contamination. In this case, lubricity problems are most likely to happen in the fuels with a lower sulphur content than 0.1%, as will soon be mandatory for use in ECAs.
“The reduction of sulphur is often blamed for the problems of lubricity with modern fuels. This is not entirely true, as the same refining process during which sulphur is removed also removes other natural lubrication components. This means that fuels with similar sulphur levels can have different lubrication properties, and sulphur level is not always a safe indicator for lubricity properties of a fuel,” says Mr Östlund.
Most distillate fuels are vulnerable to degradation that can cause colour change, gum and sediment formation. These can have a severe effect on quality during long term storage and can also induce corrosion. “What is not widely known is that distillate fuel is treated by the refinery with a stabiliser to protect it against deterioration for six months,” says Mr Östlund. “When these six months are elapsed, the fuel is more or less unprotected from further deterioration. Owners should consider carefully the addition of a multi-function fuel stabiliser during bunkering which will add protection against oxidation, sedimentation, colour change and corrosion.”
There is a clear need for regular testing and treatment to ensure that maximum value can be extracted from the fuel, he says. Testing is the first step in beginning a treatment process when problems are suspected, and it is important that potential problems are detected early and steps taken to avoid the time and cost of later remedial action. “Many of the problems encountered on board ship are not related to operation of the engines, but to the fuels used. This clearly underlines the need for fuel treatment to be integrated into the vessel’s maintenance schedules.”
Building on 30 years’ of experience, Wilhelmsen Ships Service’s Unitor FuelPower range applies advanced technologies to make certain today’s fuels can be used with confidence, regardless of fuel stability or slow steaming, says Mr Ostlund. The range for use with residual fuels includes FuelPower Demulsifier, an updated demulsifier designed to cope with high water levels in oil emulsions, FuelPower Conditioner, a new treatment for unstable and incompatible fuels which improves fuel reliability and FuelPower SlowSteam, a low dosage combustion enhancer and stabiliser. The new product range, known as Unitor DieselPower, has been specifically developed for distillates, keeping them bright, stable and trouble-free, with fewer problems resulting in lower costs in operation.
Within the marine lubricants market, new fuels, including LNG, underline the need for new cylinder oils, says Serge Dal-Farra, global marketing manager for Total Lubmarine. “Selecting a lubricant that offers optimum value is down to a vessel’s own unique operational conditions with influencing factors including ship patterns, engine layout and retrofit equipment,” he says. “Such is the complexity of the decision, that Total Lubmarine has devised a tool for customers which highlights how the operating expenses of a vessel are influenced by the lubricant feed factor. This can vary considerably between new vessels, which are required to follow OEM guidelines while under warranty, and older vessels, which have more flexibility over the feed rate.
“For example, our Talusia Universal 100 cylinder lubricant, part of the Talusia range, is more cost effective for vessels operating a MAN 8.1 engine and newer, whereas the lubricant’s sister product Talusia Universal, can be the cost effective solution for MAN Mark 7 engines and older.”
Total Lubmarine has developed new molecules able to bring BN without risk of deposit formation. Ashfree neutralizing molecules (ANM) are now a solid alternative to the calcium overbased detergents found in conventional lubricants. Due to their perfect solubility in all kinds of base oils, ANMs are stable and compatible when mixed with other cylinder lubricants, but they are also able to react much faster with acids than traditional calcium carbonate.
ANMs can match the performance requirements of different fuels including second generation single-cylinder oils for engines burning a range of sulphur content HFOs and the cylinder lubricants dedicated to dual fuel 2-stroke engines burning LNG and distillate or HFO. Cylinder lubricants combining the experience of the conventional calcium carbonate Talusia Universal chemistry and the advantages of ANMs are currently being tested.
Using LNG should eliminate the problem of cold corrosion, as there is no sulphur (except in the pilot fuel), which is a major advantage. However, the combustion process in engines using LNG is quite complex and different, therefore it requires a new lubricant. Total Lubmarine already has products for four-stroke engines that run on LNG, and the company is currently developing a lubricant that will also function for two-stroke engines.
“We expect to see a new operating landscape with the increased uptake of LNG, distillates/lower sulphur fuels and dual-fuel engines. We’ve known for some time now that flexibility is critical to success in today’s maritime market, due to the complexity of ship operations. The new generation of lubricants will be flexible and compatible with a wide range of fuels,” says Mr Dal-Farra.