Measures in hull management
Undertake both technical and operational measures to maintain a smooth hull surface, and ultimately reduce fuel consumption. These measures include regular hull inspections, maintenance and reducing time at anchorage to limit hull fouling.
Planned maintenance and hull cleaning
The most fundamental measure of hull roughness management is through the Planned Maintenance System (PMS). Hull maintenance includes a complete survey of the hull in dry dock twice in 5 years. Such dry-docking maintenance allows the inspection, repair, and cleaning of the underwater hull, which is not accessible during ship’s operations.
Hull cleaning is necessary in mitigating hull’s biological roughness. Proper cleaning of light slime can reduce fuel consumptions by 7% to 9%, while heavy slime cleaning reduces that up to 18%. Removal of macro fouling caused by barnacles can account for significant fuel savings of about 20% to 30%.
Time-based maintenance is insufficient given the impact hull roughness has on dynamic CII ratings. It is prudent to continuously monitor ship performance with the help of data intelligence, hence condition-based maintenance is preferred. This involves sensors and Artificial Intelligence (AI) to detect and monitor performance levels, which indicate when cleaning is required.
Performance-based systems track change in fuel consumption levels and main engine power through data collection to identify degrading hull conditions and timely maintenance. Consider the following when undertaking hull maintenance:
- Data such as 24/7 voyage data monitoring and analysis
- Current (voyage wise) and forecasted CII rating
- Last drydock
- Cost-effectiveness and potential savings
This system of monitoring allows effective evaluations to achieve continuous improvement.
Through such measures, operators can proactively manage structural defects and anomalies early to mitigate risks and avoid more costly repairs. These fuel savings satisfy decarbonization objectives and help in improving all CII ratings from E to D and D to C etc.
Applying a coat of antifouling paint is another approach in preventing hull fouling and preserving its smoothness. At present, many environmentally friendly products such as low friction coatings and metal-free antifouling coatings are available. These high-quality paints keep the hull polished with minimum fouling for a longer period.
Some advanced anti-fouling paints provide an ultra-smooth surface and can save up to 10.8% fuel as compared to a conventional anti-fouling paint. An alternative type of coating using silicone or fluoro-silicon base is also available. This paint utilizes nonstick properties to mitigate adhesion of bio-organisms through its extremely smooth surface, shedding any micro and macro growth during the ship’s motion.
Another type of coating addresses other causes of hull surface imperfections. This covers and smoothens welding seams present on the hull through coating with a special modified epoxy. This reduces turbulence and drag to obtain 2.5% fuel savings.
With the rising need for energy-savings and low emission targets, advancement in anti-fouling coating technology is bound to progress. However, the degree of fouling reduction will vary with trading pattern and operational profiles, regardless of the coating type used. It is important to ensure regular maintenance and repainting of these coatings due to damage and deterioration over time.