Oil system maintenance is the key to clean diesel

CJCTM Mariel Diesel Purifier with Variable Flow Control CJCTM Mariel Diesel Purifier with Variable Flow Control
Industry Database

C. C. Jensen writes for WF&A on the importance of ‘clean diesel’.

Increased system component and oil lifetime, virtually no unplanned stops and no cleaning of oil tanks are what most skippers and engineers dream of, but experiences from commercial freight vessels, ferries and fishing vessels show that these results can be achieved with proper oil system maintenance.

The most common reason for engine failure is contaminated diesel. The contamination could lead to a large number of problems and ultimately to a complete engine stop.  The contamination of diesel is very often caused by microorganism – also known as diesel bug. Diesel bug is a result of microorganism in the diesel and can be bacteria, yeast, fungus or others, and they all thrive on organic material (such as diesel), moist air or water and at certain temperatures.  

New oil is not clean
A clean tank and piping system is no guarantee for clean diesel. Tests may indicate water and/or particle contents, but microorganisms may not be indicated. Diesel bug can develop in the tank as a result of moist air, free water in the diesel and high temperatures.  It can also enter the tank via a contaminated filling system or contaminated land storage facilities. When bunkering diesel, contaminated diesel may be taken on. Once in the tank, the diesel bug can be very costly to get rid.

There are various parameters that have to be considered when looking for equipment to clean diesel. The fineness of in-line spin-on filters on the engine varies from 10 to 25 micron - thus very low dirt-holding capacity. The fineness of 10 to 25 micron will result in removal of up to 10% of the particles in the diesel. According to analysis of the distribution of particle sizes in diesel, only 10% of the particles are larger than 10 micron. Hence, the small particles, <10 micron, constitutes up to 90% of the particle contamination in the oil.

The tolerances in feeding pumps and nozzles are smaller than 10 micron and the particles fitting into these tolerances are those creating the wear and tear and, in worst case, an immediate breakdown.  If the nozzles on the engine are frequently changed, then it could be down to the diesel cleaning system not removing the small particles.

Some fishing vessels operate with several tanks with oil centrifuges, water separators and inline filters to clean the diesel before entering the day tank.  These measures may - provided they are operated correctly - work to some extent when it comes to the removal of water and smaller amounts of particles, but they will have little or no effect on the microorganism. Furthermore, the user never actually knows the effectiveness of the centrifuge.

In order to have absolutely clean diesel, all particles need to be removed, all water molecules and the microorganism causing diesel bug.  The solution is to go offline, with an offline diesel purifier unit with a large capacity and the ability to remove microorganism, particles and as well as water.

Danish company C. C. Jensen has manufactured offline oil filters and diesel purifiers for more than 60 years. The CJC™ Diesel Purifier is easy to install and is well suited for newbuilds as well as retrofitting.  It is possible to install the diesel purifier using the same pipes and connections from the centrifuge.  The CJC™ Diesel Purifier is extremely simple to operate and, as a standard, it is fitted with Variable Flow Control, which results in energy savings as the flow can be adjusted whether operating at sea or harbour.


A progressing cavity pump with EHEDG certification – is that really new?

The EHEDG (European Hygienic Engineering & Design Group) was founded in the last century at the end ... Read more

Economic and environmental advantages of the two-speed gearbox

Finnøy Gear & Propeller’s two- speed gearbox is used on vessels with large differences in power need... Read more

Leading specialist in design and manufacturing of gearboxes and propellers invests in CNC lathe for future product development

Norway- based Finnøy Gear & Propeller have recently invested in a new high- performance CNC lathe ma... Read more


Macduff Ship Design have over the past 10 years spent considerable time specialising in the design o... Read more

Kinarca participated in the construction of the most ecological, efficient freezing trawler.

Kinarca participated in the construction of the most ecological, efficient freezing trawler with gre... Read more


Cordex maintains a permanent stable growth on its CordexAqua segment – Ropes and Yarns for Fishing &... Read more

View all