Lacquering and varnishing are not new but a new deposit, particularly associated with ULSD is forming inside the injectors, we examine why this is happening and how to stop it.
Internal Diesel Injector Deposits (IDID) - Traditionally, coking deposits tended to build up over time, affecting engine performance very slowly such that the effect on fuel economy and performance was not immediately evident. Now it seems IDID can have a much more abrupt impact. IDID issues have reportedly developed over as little as 100 hours. In other cases, engines that appear to operate perfectly at the end of the working day experience starting issues after shut down.
Fuel is constantly changing to become more environment friendly. In order to meet the exacting regulations engine design has advanced significantly while still having to meet the needs of the end user. The injector is at the forefront of these changes and is at the heart of fuel optimisation. Modern injection systems now rely on extremely high pressure common rail systems delivering fuel direct to the injectors at up to 45,000psi, a pressure unheard of a few years ago. The injector holes are finely honed into complex shapes to an exact design. To hold back this pressure there are exceptionally fine tolerances between the moving parts, often just a few microns, for comparison: human hair is almost 50 times bigger at typically 100 microns. Couple this with the fact that refiners now extract much more fuel from a barrel of oil than they did in the 1990’s and the barrels are from oil fields that were classed as uneconomical and of poor quality in the 1980’s. Therefore it is clear that the IDID issue needs to be addressed, managed and solved.
There seems to be two distinct types of deposit, ‘waxy’ or ‘soap’ like deposits and carbonaceous or lacquered deposits (gumming). Combinations of fuel additives such as mono-acidic lubricity improvers and conventional succinimide deposit control additives have been suggested as a possible cause. However, in tests carried out by one of the biggest global chemical manufacturers, no evidence was found that these additives contributed to IDID, when the injectors were disassembled they had completely clean internal parts. There is however evidence that the use of bio-diesel and ultra-low sulphur diesel (ULSD) could be a factor to consider. Not only does bio-diesel contain trace metals that can intensify injector formation, biodiesel oxidation products can contribute to deposit accumulation. Carboxylic acid formed during biodiesel oxidation can corrode iron surfaces to yield an iron carboxylic salt layer. This salt layer can then trap other components in the fuel such as polymers that are also formed during biodiesel oxidation. Temperature can also have an effect, when in excess of 300 degrees Celsius the thermal condensation and cracking reaction of diesel has been shown to accelerate the rate of deposition in the nozzle and appears to be the critical threshold for coking. Marine engines use the fuel for cooling, ULSD was never meant to do that, oils used for this purpose are packed with additives to maintain stability, it is little wonder the humble diesel fuel degrades and breaks down.
Regardless of the cause, the challenge is to develop and bring an additive solution to the market that can address both the traditional coking issue and the modern IDID problem. At MarShip UK we are working with some of the world’s biggest chemical additive manufactures and have produced a range of additives to address specific problems caused from using modern day diesel.
From our DieseAid range of products, DieselAid LD is targeted at addressing the problems of both coking and IDID coupled with an added lubricity agent which ensures the micro-tolerances are maintained, essential when using ULSD with questionable lubricity. An extremely small dose rate is enough to maintain a clean and efficient fuel system, optimizing fuel consumption. Additionally DieselAid LD helps to ensure fuel systems quickly meet ECA legislation after passage on heavy fuel.
Keeping fuel injectors at optimal performance is the key to maintaining fuel efficiency, maximum power and meeting emission regulations. With modern design bringing more efficient electronically controlled injectors with ultra light pintles and such fine tolerances on the moving parts it is evidently essential to keep engines as clean as possible. Many tests indicate that increasing additive treatment rate can achieve full control of deposits within a short time frame. It is therefore vital for ship operators to protect their engines and the DieselAid LD presents a simple straight forward solution to this most complex of issues.
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Peter Weide is MD of MarShip, a UK based company specializing in optimising the efficiency of marine diesel engines. Advising on maintaining the cleanliness of Air, Fuel and Lubricating oil, we regularly recommend solutions to operators and appear regularly in industry press, with our full range of diesel additives DieselAid we can offer solutions for most operating conditions and wont advise them if you don’t need them.