Therefore, it is necessary to ensure that fuel oil used onboard a vessel is monitored and given correct treatment before use.
Problems can surface even with “on-spec” fuels
Engine problems that have been encountered as a result of inadequate treatment of fuel include wear of piston rings and liners, corrosion of post-combustion parts, clogging of engine filters, and reduced energy levels in the fuel. Many of these cases can lead to substantial repair costs and operational downtime. Nonetheless, these are situations which can be mitigated by having insight into what type of fuel is entering a vessel’s engine.
Simple solution
A Fuel System Check programme built for testing the fuel at critical points in the fuel system allows a vessel to have access to the condition of the fuel at these critical junctures. In addition, analyses of cat fine, sediment (Total Sediment Potential), water, and sodium levels are carried out to determine if the equipment is operating efficiently.
Damage caused by cat fines
The ISO 8217:2012 marine fuel specification has a limit of 60 mg/kg for catalytic fines (aluminium and silicon) whilst most engine manufacturers recommend levels of 15 mg/kg or less at the engine inlet. There have been several cases where liners and rings have been damaged, and in some instances, engine failure has resulted even when cat fine levels have been reduced to 30 mg/kg – half the ISO 8217:2012 limit. It is very important to monitor these hard particles as most heavy fuel oil deliveries around the world will require the reduction of the cat fine levels to avoid wear on engine components.
Other risks
Other risks include water and sodium contamination. Water in the fuel can lead to a reduction in fuel economy as the specific energy of the fuel is reduced by its presence. If the water present is due to sea water ingress, then corrosion of engine components is probable with poor separator efficiency. Sodium can also originate from the refining process and be present in the fuel as given from the supplier. The effects of the presence of sodium in the fuel is the corrosion of exhaust valves and high pressure parts of the fuel system. Another effect is an increase of deposits in the post-combustion spaces.
Monitoring Sediment Potential
Unstable or “dirty” fuel oil is another issue frequently dealt with by marine vessels. Unstable fuel oil can indicate that a fuel has a low reserve stability. Asphaltene molecules must remain in suspension in order for a fuel oil to remain stable. If these molecules fall out of suspension, sludging occurs. Inorganic matter can also be present in the form of dirt, grit, or clay. These contaminants are sometimes present in the different fuel streams used to make marine fuel oil and can lead to high sediment levels. When sediments are produced it can lead to build up in storage tanks and piping systems. It is important to know the sediment potential of fuels as many times an unstable fuel with poor asphaltenic properties can lead to more serious issues when mixed with another fuel. In severe cases, fuel with high sediment potential can lead to blocked separators and filters creating high maintenance situations for a vessels crew. Monitoring the sediment potential of the fuel on board your vessel can help keep a bad situation from getting worse.
Regular fuel system checks to mitigate risks
As each batch of fuel purchased tends to have different physical properties, it is important to have a robust fuel monitoring programme in place, meaning that every bunkers should be tested.
In addition to routine testing at least once a quarter, fuel system samples should be taken to perform the standard battery of tests to help the ship’s crew mitigate the risks involved with the quality of the fuel and to take preventive action, if needed. This ensures that the fuel treatment system always operates at optimum efficiency by enabling a vessel’s crew to take corrective action more quickly
The fuel treatment system is the single most important protection for vital engine components. Hence, enlisting a vessel in a comprehensive programme to ensure the efficiency of the fuel treatment equipment, is a proactive measure that can lead to more efficient engine operation as well as peace of mind for a vessel crew and its managers.
Financial benefits and ‘peace of mind’
With the current headwinds in the global economy, identifying such risks to the engine components is now more important than ever as ship operators and owners seek new ways to reduce costs and stay profitable. The financial benefits of avoiding the pitfalls involved with marine fuel oil cannot be overstated and can provide a practical way to keep valuable finances for other endeavours.
By enlisting in a sound fuel system programme, a ships operator and crew members can rest easier knowing that they have taken the necessary precautions to minimize the more ominous situations that could lead to loss of propulsion or power.
Christian Ryder is Technical Manager, Americas at Veritas Petroleum Services.
Email: [email protected]
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