Diesel is losing lubricity

Why Diesel is Drying-Out?

Loss of lubricity is an unintended side effect of ECA requirements

From the 1st January 2015, vessels operating in designated emission control areas must use fuel with a sulphur content no greater than 0.1%.  While we all understand the reasons behind this decision, do we fully understand the impact this change is having on our engines?  The feedback from our customers suggests not, so hopefully we can shed some light on the issues.

The introduction of lower sulphur levels has brought a huge range of side effects in relation to storage, combustion, ignitions and lubricity of diesel.  While most of us are familiar with the microbial problem (Diesel Bug) many underestimate or are unaware of the effects of loss of lubricity. 

Why Fuel is Losing Lubricity

It all comes down to the way in which sulphur is removed from diesel.  The most cost effective way is to use hydro-processing, during this process the sulphur is removed and replaced by hydrogen; however, hydrogen is a highly reactive element and reacts with other components in the fuel and removes the polar and aromatic compounds that provide conventional diesel fuel with adequate lubricating capability.

Why Lubricity is important

All diesel injection equipment has some reliance on diesel as a lubricant, so it’s easy to understand how important its lubricating properties are,  especially for rotary and distributor type fuel injection pumps as found in today’s modern common rail injection systems. In these pumps the moving parts are lubricated by the fuel itself as it moves through the pump rather than the engine oil.  Other diesel fuel systems such as injectors, unit injectors, unit pumps and in-line pumps are also partially fuel lubricated.  In these systems the mechanism typically consists of a plunger or needle operating in a sleeve or bore, the fuel is used to lubricate the walls between the reciprocating piece and its container.  So logically if the fuel loses lubricity there will be an increase in the amount of wear or scarring that will occur between two metal parts requiring fuel lubrication as they come into contact with each other.  Low lubricity fuel may cause higher wear and scarring thereby shortening the component life.

We know that without lube oil a diesel engine will grind itself to a premature death, we can now say the same about fuel components.

The issue is considered serious, so much so that the International Council on Combustion Engines ( CIMAC ) have set up a subgroup to advise on how best to deal with engines running on low sulphur fuel.  In their document ‘Guideline for the operation of marine engines on low-sulphur fuel’ they highlight lubricity as one of the most important issues to consider and state that lubricity characteristics can be restored using lubricity improving additives.  Also according to FOBAS from Lloyds Register, fuel with less than 0.05% is dry and they also strongly recommend lubricity is added.  We have seen fuel analysis reports showing sulphur at 0.03% – the lowest the tests can report on, so worryingly the actual sulphur content could be even lower.

Approaching the issue Intelligently

So here at Marship, being fuel specialists we started working with one of the biggest global chemical additive manufacturers who supply the world’s largest oil companies.  Our aim was to go beyond the standard ‘catch-all’ additive where typically you find yourself paying excessive amounts for a ‘package’ of additives that you don’t need.  Instead we have tried to take a more intelligent approach by producing additives aimed at addressing specific fuel problems.

Many vessels only need a lubricity additive, hence the introduction of DieselAid L. This is the right place to start for responsible fuel management.  It is true that with today’s modern common rail engines and extremely fine tolerances  there is also the issue of  gumming and trumpets forming on nozzles, this is when deposit control needs to be considered. Watch out for our next article that talks about this very issue..

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Peter Weide director MarShip UK

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.

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