Harsh realities of modern diesel’s effect on marine engines

Shows filters blocked with Diesel Bug

Shows filters blocked with Diesel Bug

Today’s diesel fuel is very different to the diesel that was supplied a few years ago; quality has steadily decreased as supply chains have increased and new emission control standards have resulted in ULSD (Ultra Low Sulphur Diesel) and biodiesel finding their way into the supply chain. Peter Weide of MarShip UK examines the implications of this and what users can expect.


What are the new requirements?

From now on ships trading in designated emission control areas will have to use fuel oil on board with sulphur content no greater than 0.10 per cent. Considering how many people contacted us last year with fuel issues when the allowed amount of sulphur was a whole 1.00 per cent it’s evident that this is going to be the year of the Diesel Bug and other such complications.

What are the implications of Low Sulphur Fuel?

Everyone agrees and understands the need to move to low suphur fuels; however, losing the sulphur from fuel will impact in three key areas:

  • Contaminants
  • Deposit Control
  • Lack of Lubricity

Contaminants – aka – Diesel Bug

Diesel Bug is the collective name for the microscopic fungi, yeast and bacteria that are present in fuel, as diesel is organic these will always be present. The problem starts with water contamination in fuel.  There are many different reasons why fuel contains water for example from absorption, the supplier or condensation, but be assured all fuel contains some water. Diesel bugs attach themselves to the water droplets and sink to the bottom of the tank where they feed from the fuel above. They double in number every 20 minutes, living for 18 hours they excrete waste and die leaving the all too common sludge at the bottom of the tank. Not only does this sludge clog filters and stop the engine it can also corrode steel tanks, so look out for the tell-tale signs of pitting, corrosion and the smell of rotten eggs which indicate a serious problem. Why has removing sulphur caused an increase in diesel bug? Sulphur is a natural biocide, removing it means there is nothing to stop the bug taking hold.

Deposit Control

Along with traditional coking commonly found on the injector tip and spray holes, the advent of low sulphur diesel has introduced Internal Diesel Injector Deposits (IDID) which are found inside the injector body. There are two distinct types of deposits, ‘waxy’ or ‘soap’ like deposits and carbonaceous or lacquered. These deposits can slow the response of the fuel injector or cause sticking of the internal parts. This in turn can result in loss of control of the injection event timing as well as reducing the quantity of the fuel delivered, both of which will impact on how the engine performs. A build-up of these deposits can lead to rough engine running. Older engines with greater tolerances are less likely to be affected but modern injection systems which 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.  To hold back this pressure there are exceptionally fine tolerances between the moving parts, often just a few microns. IDID issues have reportedly developed in as little as 100 hours and in other cases engines that operate perfectly at the end of the working day experience issues only when next started.

Lack of Lubricity

All diesel injection equipment has some reliance on fuel as a lubricant, especially for rotary and distributor type fuel injection pumps as found in today’s modern common rail injection systems.

Fuel refiners have had to develop new technologies to remove the sulphur while not losing performance and power or the end user. The most effective way to remove sulphur is through a process called hydro-processing. During this process the sulphur in the fuel is removed and replaced by hydrogen resulting in a cleaner burning fuel with improved performance. Unfortunately as hydrogen is a highly reactive element and increases the likelihood of IDID it also ‘reacts’ with other components in the fuel removing the polar and aromatic compounds that provide conventional diesel fuel with adequate lubricating capabilities. As with the deposit control issue, the tolerances are so very fine between the moving parts, that this lack of lubricity can easily cause higher wear and scarring, ultimately shortening component life.

How can you safeguard your engine against the effects low sulphur fuel?

There are probably as many options as there are fishing boats and it is very easy to get swamped by all the information out there. Given the lubricity and deposit issues caused by low sulphur diesel we would recommend that everyone has a robust additive programme that offers your engine the best protection – especially if you are operating a modern common rail system. The important thing here is to see behind the hype and get a reliable product tailored for the appropriate issues, such as those in our DieselAid range which are designed to address specific issues rather than the common catch-all products where you are paying for chemicals you probably do not need.

What about the Dreaded Diesel Bug?

A serious case of Diesel Bug which we helped bring under control

A serious case of Diesel Bug which we helped bring under control

There is only one sure fire way to ensure that you do not have issues with diesel bug and that is simple – remove the water from the fuel. There are additives available that will kill Diesel Bug, but they will only deal with the fuel you dose at the time you dose, so next time you fill up you have a whole new tank of fuel with some water and residual bugs.

The best way to tackle all three issues to install a Fuel Purifier to remove the water which will ensure Diesel Bug is not an issue and then regularly dose with a credible additive that contains a little biocide along with an added lubricant and cleaner to minimise the risk of deposit build up.

MarShip UK specialise in maintaining the vital elements of your engine – Air, Fuel and Oil. Their range of DieselAid Additives are designed to address specific fuel issues.

For free advice please contact them sales@marship.eu / 0845 287 1546 / www.marship.eu


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