When Texaco, now represented in the marine lubricants market by FAMM (Fuel and Marine Marketing), launched Taro 40 XL 40, the lubricant was designed to address pressing field problems in medium speed engines. Three years later FAMM is in a position to evaluate the performance in a large number of engines and to compare the field results with competitive lubricants. The pressing problems arose from a series of engine design and fuel processing changes
. Although aimed at improving engine efficiency and making savings, the changes resulted in a series of difficulties. The best known are engine blackening, undercrown deposits, piston head corrosion, fouling of purifier heaters, increased oil consumption, base number depletion, oil scraper ring clogging and increased piston deposits. To operate the new medium speed engines satisfactorily, a new generation of lubricants was needed. The new oils had to be able to disperse high concentrations of cracked asphaltenes in the lubricant and have enhanced thermal stability to resist extreme temperature conditions.
To understand the impact of the new lubricant generation on the field performance, it is necessary to look into the causes of the field problems and the working mechanisms of the new lubricants.
Engine blackening through fuel contamination
In modern medium speed diesel engines the fuel pump pressure has been increased, sometimes up to 1600 bar. This contributed to high fuel pump leakage and increased fuel contamination of the lubricant. Analyses of used oils from medium speed engines running on heavy fuel (HFO) indicated an average HFO contamination of two percent. In some cases levels up to 15 percent were detected.
Most of the HFOs in use today come from cracking installations. The cracked asphaltenes, an inherent part of modern HFOs, don't dissolve in lubricants but instead coagulate and form floating asphalt particles of two to five microns. These particles are very sticky and form black deposits on all metal surfaces
of the engine. These result in black deposits in the cambox and in the crankcase. The deposits also cause oil scraper ring clogging
. This can lead to high oil consumption
Deposits are also formed in the hot areas of the engine such as the piston grooves, the piston lands and in the cooling spaces of the piston. If an oil barrier
is used to seal the fuel pump, asphaltene coagulation can occur on the surface of the fuel pump plunger, sometimes leading to fuel pump blockages. These deposits can obstruct the fuel pump drain. This results in excessive fuel ingress into the lube oil, aggravating the deposit problems and causing serious viscosity increases due to fuel admixture.
Significant differences in the degree of blackening can be observed in the field. The differences are largely due to purification conditions and fuel pump type. The problems can be minimised by effective purification, which removes the asphalt particles from the lubricant. Extreme engine blackening is experienced in case of poor purification in combination with high HFO pump leakage.
It was to resolve these problems that the new lubricant technology was developed. In the latest generation of lubricants, asphaltenes are dispersed in the lubricant.
Inspection of a high number of engines of different makes, which have accumulated up to 20,000 hours with Taro 40 XL 40, show excellent general cleanliness and considerably improved piston cleanliness. Excellent results are obtained even with high HFO contamination levels up to 8 percent. Product testing in the laboratory and engine inspections in the field indicate that there is a substantial difference between the performance of the different commercial oils on the market. In particular, the amount of asphaltenes that can be dispersed is significantly different. This is reflected in the high number of dirty engines still found in the field. Engines with a relatively high level of HFO contamination and a moderate oil quality still suffer asphaltene deposits, heavy deposit formation in purifiers, in purifier heaters, high filter consumption etc.
FAMM found that of all the tested commercial lubricants, Taro 40 XL 40 was able to disperse the highest level of cracked asphaltenes. Nearly all engines lubricated with Taro 40 XL 40 were fully clean. Excellent piston cleanliness was obtained. The cleaning intervals of the purifiers were reduced as was, in many cases, filter consumption. Deposit formation in purifier heaters was almost eliminated.
The field results obtained with Taro 40 XL 40 are illustrated in Figures 1 to 4.
They show the cleanliness obtained with the new lubricant as compared with the previous generation of oil. Figure 1 shows typical blackening of a cambox due to 4percent HFO contamination of the lubricant.
Figure 2 shows a cambox lubricated with Taro 40 XL 40, despite a high HFO contamination level of 4 percent, the blackening is fully eliminated.
Figures 3 and 4 compare crankcase cleanliness in an engine with 4 percent HFO contamination before and after the use of Taro 40 XL 40.
Due to the continuous increase in output, the piston cooling space temperatures have been increasing. The piston undercrown temperature is typically about 250°C. In the latest engines, temperatures of 300°C have been measured. This can cause carbon deposits on the piston undercrown due to thermal carbonisation of the lubricant. The carbon deposit layer forms an insulating layer upsetting the piston cooling increasing the piston temperature. Temperature increases of around 100°C have been measured.
A second deposit formation mechanism is the adhering of the asphalt particles that originate from HFO contamination. The build up of such a carbon layer in the piston coolant chamber is illustrated in Figure 5.
To cope with the extreme temperature conditions, especially in highly loaded engines, the thermal stability and oxidation stability of lubricant had to be substantially increased. FAMM has found that the thermal stability and oxidation stability of Taro 40 XL 40 has matched and even exceeded a number of synthetic commercial oils.
Figure 6 shows a similar piston cooling space of an engine lubricated with Taro 40 XL 40. No carbon was formed in spite of very high cooling space temperature (300°C) and HFO contamination of 4 percent. This was due to a combination of thermal stability and asphaltene dispersion technology.
Piston Head Corrosion
Undercrown deposits in combination with high load operations can lead to piston head corrosion. Undercrown piston deposits inhibit cooling, resulting, as already mentioned, in an increase of about 100°C in piston temperatures. Above 450°C, some sodium/vanadium salts form a melt with the piston crown material, causing hot corrosion on top of the piston. In case of high load operations and reduced piston cooling, the critical temperature is easily reached at the top of the piston. As a result, material melt and material removal by hot corrosion is occurring. This means earlier replacement of the piston crowns and, in severe cases, hole formation in the pistons, a problem which could endanger the safety of a ship.
Field inspections of a number engines lubricated with Taro 40 XL 40 indicate that in nearly all cases the piston undercrown deposit problems were eliminated. Very severe applications, such as power plants in the tropics running constantly at 100 percent load, were included in the study.
Looking back at the experience of the last three years, Roger Stubbs, FAMM's General Manager Lubricants Europe, sees Taro's success as further evidence that marine lubricants cannot be regarded as just another commodity. He said the lubricant had shown 'outstanding' levels of cylinder and crankcase protection at a time when high output engines with high internal temperatures and pressures and reduced oil consumption
had become the norm.
By Ing. A. Verhelst, of FAMM's Marine Lubricant Technology Department.
First published in Marine Lube Buyer, March 2000.
Online Fuel Supplier Fueled By Support
Online marine fuel supplier OceanConnect signed a strategic alliance with ship broking group Horace Clarkson Plc. "Clarksons will support OceanConnect.com's initiatives to develop credit insurance and swaps capability to the online marine fuels marketplace," the company said. Clarksons, the world's biggest shipbroking group will also become an equity partner in OceanConnect. In the last month OceanConnect has announced partnerships with shipping companies Eletson Corporation, Keystone Shipping Co and Stena Bulk AB plus Japan's Nippon Mitsubishi Oil Company and energy information provider Petroleum Argus. Scheduled to begin operations in late spring, OceanConnect said it aims to provide a fast and price-efficient marketplace for marine fuel transactions plus real-time information on pricing and product availability. Other investors include BP (BP)
Marine (a unit of BP Amoco), Fuel and Marine Marketing LLC
(a joint venture between Texaco
and Chevron (CVX)
) and Shell Marine Products (a Royal Dutch/Shell unit).
ExxonMobil Forms New Global Team
ExxonMobil has established a new global marine lubricants organization, which is part of the company's Lubricants & Petroleum Specialties Company. The new team is comprised of executives from both former companies with a combined total of 60 years of marine lubricants experience. The new group includes: Mark P. Andreotta, vice president, Global Marine and Aviation Lubricants, Fairfax, Va.; Ray J. Pomfret, regional manager, Africa, Europe and Middle East, Leatherhead (Esso Petroleum); Tom Arne Ingovoldstad, regional marine manager, Asia Pacific, Singapore (ExxonMobil Asia Pacific Pte.); Andy Janssen, regional marine manager, Americas, Fairfax, Va. and Keith P. Saddler, Global Equipment Builder and Marine Products Manager, Fairfax, Va.
The company also appointed Steve Walker as technical manager to oversee the implementation of an Operations Integrity Management System (OIMS).
Fuel-Tek Touts New Fuel Conditioner
Florida-based Fuel-Tek has developed a new fuel conditioner specially designed for the marine market - Fuel-Tek Marine CAL-5 - a multifunctional additive package. The product addresses every fuel storage and handling problem encountered within the maritime industry. Cal-5 is a fuel stabilizer that contains surfactants, non-ionic dispersants and organic combustion catalysts coupled with proprietary FAB-20 technology. This conglomeration offers an environment that is unsuitable for the formation and growth of fungi, algae and bacteria. Cal-5 also eliminates soot in the exhaust stream, lubricates the fuel system, extends filter life and disperses water. A 16-ounce bottle will treat 640 gallons and a one-gallon container will treat 5,000 gallons.