Article from the U.S. Coast Guard Proceedings of the Marine Safety Council,
July-Sept, 1996, Vol. 53, No. 3, "How Technology is Affecting the Maritime World".

Controlling Microorganisms in Diesel Fuel
... A New Solution to an Old Problem
By Mr. F. X. McGeechan

The Marine industry has long been plagued with the problem of "bugs", the microorganisms that live and grow in fuel, fuel tanks, cargo and ballast tanks and lube oil systems. This contamination problem has grown to such proportions that it is considered almost epidemic. New technology is now available for permanently eliminating microbial contamination problems in a clean, safe and environmentally friendly manner.

The basis for growth of microbes is water. All fuel oil contains some water and, therefore, microbes in varying quantities. These "bugs" flourish at the oil/water interface, using the oil as their food source. Temperatures normally experienced in engine room environments (60 to 95 degrees F) provide ideal breeding conditions. Most affected are light oils, e.g., MDO (marine diesel oil), GO (gas oil), some lubricants, and generally any oil with a boiling point below 700 degrees F. Although less common, heavier fuel grades are sometimes affected but fuel heating often resolves the problem.

"Bugs" present many problems to shipsâ engineers. These include filter plugging, clogged fuel lines and high rates of corrosion in fuel tanks, ballast water tanks and bilges. It has become so prolific that the IMarE has appointed a special subcommittee comprised of authorities including IMO and shipping industry representatives to study the problem and recommend solutions. Some aerobic microorganisms, commonly referred to as "algae", if left unchecked will grow into colonies, forming mats or long strings of seaweed like structures. Other bugs, anaerobic ones, known as SRBs (sulfate reducing bacteria) are referred to as "metal-eating bacteria". They combine with moisture to produce sulfurous acid that is responsible for corrosion in fuel components, injectors, and tanks. Quoting from Marine Engineers Review, January 1996, "Heavily infected fuel will, within just a few hours, result in filter plugging, fuel starvation, injector fouling and purifier malfunction. Non-uniform fuel flow and variations in combustion may accelerate piston ring and liner wear rates and affect camshaft torque."

ADVANCED
TECHNOLOGY

Although relatively unknown in the US, within the last ten years, a new technology using magnetic flux fields to combat the "bugs" and their associated problems has been developed in New Zealand. The theory that magnetic flux fields inhibit microorganism growth and survival has long been noticed. There is an old story about a Scottish marine engineer who observed that the fuel oil supply line and filters to his port generator had fewer clogging problems than to his starboard generator. He determined that the difference between the two fuel supply systems was that the port fuel line passed through a magnetic flux field. The engineer


[BACK] [FORWARD] [HOME]