Water and Contaminants in Marine Fuel Systems: A Coast Guard Safety Alert

May 19, 2022

The United States Coast Guard is alerting vessel owners and operators about the dangers of water and other pollutants in marine fuel systems. On Thursday, the Inspections and Compliance Directorate of the Coast Guard issued Safety Alert 06-22, which addressed the problem.

The safety notice follows a Coast Guard inquiry into a towing vessel’s loss of propulsion while operating in a pushing position on the Mississippi River three hours after going underway and 3.5 hours after collecting fuel from a shore side station. Thankfully, no serious damage or injuries were sustained as a result of the occurrence.

The vessel’s fuel tanks and supply system to the engine were significantly contaminated by water, to the point where the vessel’s engines initially lost power before shutting down completely, resulting in a total loss of propulsion, according to the study.

Vessel operators and engineers have long been aware of the dangers of tainted gasoline, but with improvements in fuel quality regulations and onboard purification and filtering systems, there have been fewer casualties. However, advances in primary engine designs have resulted in more accurate machining and reduced clearances in engine parts such as pumps, bearings, cylinders, burners, and injectors.

Keeping this in mind, pollutants such as sediment and water can have a negative effect on equipment intended to run on clean, water-free fuel. Furthermore, since fuel is constantly utilized while the vessel is working, continued monitoring in fuel procurement, as well as system operations and maintenance, is required to maintain its quality.

While big ships frequently have the room and power to run centrifugal purifiers, the same cannot be true for smaller vessels that solely sail on rivers or lakes. These vessels frequently have only one or two filters put directly in the fuel supply line, and those filters are not as effective at eliminating water as centrifugal purifiers.

According to the Coast Guard’s safety advisory, “the impact of water and other impurities in fuel systems can be hazardous to the operation of any vessel. From big commercial ships operating on a global scale to inland towing vessels and leisure boats, failing to assure a supply of water and contaminant-free fuel can have disastrous repercussions.”

As a result, the Coast Guard strongly advises vessel owners and operators to adopt a variety of precautions to help avoid water and pollutants in fuel. 

The fuel-check steps involve the following:

• Check that fuel supply (bunkers) fulfill engine manufacturer specifications for critical criteria like viscosity and cetane number, as well as any compliance standards like flash point and sulphur content.
• As part of a periodic maintenance system, include routine fuel oil samples and testing from service tanks.
• Confirm that fuel filters have the appropriate flow rate and filtration (micron) rating and that a sufficient stock of spare filters is carried onboard.
• Consider duplex filter systems for switching from blocked to clean filters, as well as filter differential pressure gauges for monitoring the filter element’s state and sanitation.
• To check the water content in fuels, consider installing a water sensor in the diesel tank or filter system. 
• These sensors can be used in conjunction with displays and alarms to determine excess water and are usually more effective than manual sampling at identifying rising water levels.
• Verify that a means of sampling the fuel obtained during bunkering is available, usually through a valve and piping setup.
• Prepare a plan to recover from any engine stoppage caused by water pollution in the fuel.
• Fuel that has been heavily contaminated with water or other contaminants has the potential to harm the engine in a variety of ways, along with contamination of the lubricating oil system.

The Coast Guard’s Office of Investigations Casualty & Analysis’ Safety Alert website can be checked for the record of Safety Alert 06-22.