Contaminated Diesel Results in Diluted Oil (Part 2)
With the vessel back in service and making money all seemed well. The injectors had been serviced, oil and filters in both engines changed, the Racor’s cleaned out and filter elements replaced. Magnetic decontamination units had also been fitted to the fuel lines as a way of providing ongoing treatment for the Diesel Bug problem. However, after a couple of weeks passed I received another call from the skipper. He was not happy as the Racor’s were again full of microbiological growth. He wanted to know why the magnetic units weren’t doing the job. I immediately rang the distributor of the product who in turn called upon the gentleman who invented the units. Both men stand by their product and were only too happy to come down and have a look at the problem.
They went through the test results and looked at the work we had carried out. Much head scratching went on until the skipper mentioned how he used his tanks. There were 6 x 1000 litre tanks, three a side, although the return lines only went back to the aft tanks. The skipper used each of his tanks individually as required to keep a good balance, however the balance lines between the tanks were at the top and hardly ever came into play. It was pretty quickly determined that the main problem was flow, in other words there was no circuit. For best results magnetic units need to be within a circuit, with the engines return lines going back to the same tank that the fuel was drawn from. This meant the return lines would have to be rerouted so that each tank was teed off the line. This would enable each of the tanks to receive the same amount of returned fuel all the time. Fortunately, a bit of luck made life a little easier. All the tanks had entry points in the top aft corners, with only the port and starboard aft tanks being used for the return lines. The rest were plugged off. To enable even circulation of the fuel the skipper would have to leave all the fuel valves open so that an equal amount of fuel could be drawn off from each of the six tanks at the same time.
The issue of physically cleaning out the tanks was also brought up as it was quite obvious that they were heavily contaminated. Again, a stroke of luck came our way. All six tanks had extremely good inspection ports, which were easy too get to. As the vessel was only carrying around 3000 Ltrs of fuel it meant that we could full three tanks up completely and drain the other three so that they became accessible. With the use of a large filter/fuel water separator and pump mounted on a trolley we were able to pump the fuel from tank to tank without a problem. Once each tank was empty we were able to gain access and clean them out. As the inspection ports were large and on the side of the tanks we were then able to wipe out virtually all of the Hormoconis resinae (the Diesel Bug fungi) that was stuck to the sides and bottom of the tanks. While most other microorganisms float around at the fuel water interface it is this Hormoconis resinae that will cause most of your problems. It not only has the ability to build biomass exponentially and block your filters, but it is the only microorganism that can stick to the tank floor and electrochemically drill into the surface. This can result in corrosion and pitting taking place. If left long enough it can actually drill right through the tank floor and result in fuel leaking out.
This process is started by the ingress of water either as a result of condensation drawn in through the breathers or by large amounts of water entering as a result of leaking deck filler seals, breathers that are either poorly located or not working correctly and/or fuel loading from a contaminated source. Extremely small droplets or moisture can become suspended in the fuel causing the clarity of the fuel to become affected. Larger amounts of water drop out and result in what we call Free Water. Free Water is normally easy to recognise as it sits on the bottom under the fuel phase. If there is Free Water present in your fuel it’s normally quite visible in the sight glasses on your fuel/water separators. Water creates the perfect environment for the microorganisms to grow as the individual spores can latch on to the water molecule and start to divide/multiple and grow around it thereby colonising the fuel and then tank. Often you can see this process happen at the interface between the water and fuel phases, however in this case we found very little if any obvious signs of water in the fuel. This is not unusual as it often only takes parts per million of water to start this process of microbial contamination off.
Two very long hard days graft were undertaken to complete this work, however once the job was finished the vessel was free of any major microbiological infections. The fuel now flows in a complete circuit, which includes the magnetic units and new return lines to each of the six tanks. As a result the vessel’s engines now receive clean fuel, the smoke is a lot less and the vessel is back up to full speed. And best of all the sight glasses have remained clear.
Written for Professional Skipper Magazine, Issue 78
Written By Kelvin Hieatt
Marine Diagnostics Ltd
Specialists in Used Oil and Petroleum Analysis
