Hull degradation is one of the most important vessel performance levers in shipping, but is very often overlooked. The reason for this is the high level of difficulty in computing hull degradation properly.
Only a proper computation allows a shipping company to go away from current practices, i.e. troubleshooting after a charter party consumption claim or planned maintenance such as cleaning the hull and propeller, despite whether it is needed. Usually, the speed-consumption development is monitored rather than the hull index itself.
Industry experts, ourselves included, have developed ISO 19030 to detail correct computation. This norm serves as a good basis for assessing the condition of the hull based on collected data. With more than 2,000 vessels using StormGeo’s ECO Insight Performance solution, we have discovered some shortcomings of ISO 19030:
The main downside of the ISO 19030 is that it measures performance improvements rather than the absolute level of performance. So while you will see X% improvement of performance after dry dock, you won’t know whether you came back to 100% performance.
To explain the significant improvements to ISO 19030 that have been implemented, we will first describe the basic methodology for hull performance assessment. A main KPI can be the speed-power relationship, i.e. the power increase needed to move a fouled ship forward or the loss in speed when keeping constant power. We prefer to look at the power increase needed, due to the exponential relationship between speed and power.
Steps to assess hull degradation:
As the hull performance index is a relation between ideal power and corrected measured power, it represents a simple way to understand the KPI for added resistance due to hull and propeller fouling. The hull performance index is approximately 100% for a ship with new paint and below 80% for a degraded hull.
After assessing hull degradation continuously for many ships, we not only recognized the issues above, but also took the opportunity to solve them.
Our aim is to show hull degradation as an absolute level and as a degradation trend, which is reset by a dry-docking or cleaning event.
While this development work took about one year, how can we be sure our new approach is better than the existing ISO one?