We know fuel has changed to be kinder to the environment and this has led to changes in engine design. The injector is at the forefront of these changes and the heart of fuel atomisation. Today’s modern common rail fuel systems deliver fuel direct to the injectors at up to 45,000psi, a pressure unheard of a few years ago. To achieve these pressures, tolerances are measured in a few microns, for comparison: human hair is almost 50 times bigger at typically 100 microns.
Yet as these pressures and tolerances have become ever more critical, the diesel itself has become ever more unstable.
Refiners now extract double the amount of diesel from a barrel of oil than they did in the 90’s and those barrels of oil now come from unstable base stocks that in the 80’s were seen as poor quality. The finished diesel is then hydroprocessed to remove the sulphur and in so doing removes the lubricity and makes it less stable and more prone to oxidation, gums and varnishes causing the newer modern phenomenon IDID (Internal Diesel Injector Deposits).
Traditionally, coking deposits built up over time, affecting engine performance so slowly that the effect on fuel economy and performance was not immediate. IDID deposits have a more abrupt impact. Affecting the internal moving parts, where tolerances are extremely tight and the parts light, the deposits cause binding or sticking. In extreme cases, the injector gets stuck in an open or closed position. More commonly, the parts will move slowly and not accomplish the required multiple injections with split second timing. IDID has been reported to develop in less than 100 hours.
There are two distinct types of deposit, ‘waxy’ or ‘soap’ like and carbonaceous or lacquer. Ultra Low Sulphur Diesel is also a factor as is Bio-diesel. Bio-diesel contains fatty acids and with oxidation contribute to deposit accumulation. Temperature also has an effect on Nozzle coking at 300 centigrade thermal condensation and cracking occur accelerating the rate of deposition in the nozzle.
Regardless of the cause, the challenge is to develop an additive solution which solves both the traditional coking issue and the modern IDID problem.
Taking this together with increased fuel consumption from excessive pump wear and even potential catastrophic failure means that vessel managers are duty bound to do something to aid lubricity as a fundamental of responsible vessel management, this is no longer a ‘nice to have’ it’s a must have.
DieselAid D is targeted at addressing the problems of both coking and IDID and with a dose rate of 1 litre in 8000 litres is very economical.
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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.