by Stewart Barrett, Laboratory Scientist, Energy and Environmental Microbiology Services, NCIMB
Maintaining and monitoring the quality of the diesel in your systems is an important step towards ensuring they are running efficiently, and minimising the risk of damage to vital equipment. From lifeboats to emergency generators, diesel is a widely used fuel in offshore platforms and knowing the state of your diesel can help prevent a myriad of potential issues. At NCIMB we provide the following suite of tests to analyse your diesel and give you peace of mind.
Appearance:
The appearance of diesel can tell us a lot about its quality. A darker diesel can indicate degradation – this could potentially be biodegradation caused by a large bacterial population, oxidation of the diesel caused by improper sealing or contamination by unwanted particulates. Additionally, a diesel that appears hazy can indicate a large quantity of suspended water, however a more obvious sign of water contamination is a large water phase at the bottom of the sample! What we want to see is a nice clear and bright sample.
Water content: Karl Fischer titration
An important test we carry out is analysis of the water content of diesels. This is undertaken by injecting a representative aliquot of the sample into a Karl Fischer titrator. Karl Fischer titration is a rapid and accurate method, and a popular means of determining water content that is used, not only for fuel analysis, but also in the food and beverage, pharmaceutical and chemical industries.
Water can build up in fuel tanks via condensation or poor sealing. Analysing the water content of a diesel sample is an important monitoring test because enough water in the fuel source can allow for bacterial growth. Water settling at the bottom of fuel tanks can also lead to accelerated corrosion and if this water phase were to be mixed with the fuel, it may become suspended leading to the fuel being unsuitable for use.
Particulates:
Particulates are a troublesome area of contamination for fuels that can be caused by scale or rusting of the storage vessel, or even just outside contamination from transport of the fuel. We test for the quantity of particulates in a diesel sample by filtering a known volume of sample through a pre-weighed filter and drying before re-weighing to find the weight of particulates captured in that volume. A high level of particulate matter can lead to damage or blockages of the fuel system.
Bacterial count:
We couldn’t call ourselves oilfield microbiologists without testing for microbes! This involves pipetting our diesel samples onto different medias and incubate to allow growth of whatever may be lurking in the samples, testing for bacteria, yeast and moulds.
Microbial growth in fuel tanks can be a major cause for concern, leading to potential fouling of the fuel as the microbe’s snack on it, or production of biofilms that can clog filters/coalescers. If these microbes get suspended in the fuel, then the fuel itself may not only be unusable but it may lead to contamination further down the fuel system.
Fungal fragments:
Fungi love dark, damp places to grow and, with sufficient water contamination, will be found in fuel tanks. In addition to plating out and looking for fungal growth as described above, we also test for fungal fragments by filtering a known volume of diesel through a 0.45µm filter and counting all the fragments we see through a light microscope.
While the presence of fungal fragments doesn’t indicate that the fuel is unusable, a large number can lead to problems down the line particularly with filter blockages. Shout out to Cladosporium resinae, a particular headache for the aviation industry concerning contamination in fuels.
The importance of regular testing
All of the above tests can be undertaken during an investigation to determine the cause of an issue that has arisen, but regular testing to monitor diesel fuel quality can help to prevent failures by highlighting any issues before they become a serious problem.
For more information about our diesel and marine gas oil testing services, visit our fuel testing page or use the form below to get in touch.
“The appearance of diesel can tell us a lot about its quality.”