Fouling on a ship’s hull creates friction as a vessel moves through the water. This friction increases the power needed by the ship to maintain a given speed, which in turn leads to higher fuel consumption and more emissions.
From the moment a vessel hits the water fouling will inevitably follow. Certain parameters increase the rate of growth such as warmer waters, or where the vessel is closer to the shore, or when it is slow-steaming or idle. It has been calculated that even minor fouling will have a significant impact on the ship’s hydrodynamics and fuel consumption. The smallest micro-fouling is caused by slime and can result in an increased fuel consumption of between 7-9%, as the vessel uses more fuel to counter the increased drag. Macro-fouling – seaweed, barnacles, oysters and mussels – typically increases the engine power needed by about 18- 20% over five years.
It therefore comes as no surprise that in today’s challenging markets this increasing cost is one that few shipowners or operators can afford. Add to this the stricter environmental regulations coming into force, such as the International Maritime Organization’s (IMO) impending sulphur cap of 0.5% in January 2020, and this has driven an increased focus on fuel efficiency.
Worldwide coatings manufacturer Hempel recognises the need for sustainable solutions to help maximise operational efficiency, which is why it launched SHAPE (Systems for Hull and Propeller Efficiency) last year.
SHAPE is founded on the ISO 19030 standard that describes how to measure the changes in ship specific hull and propeller performance and defines a set of performance indicators for hull and propeller maintenance, and repair activities. Based on these principles, SHAPE monitors a vessel’s long-term trends using in service key performance indicators (KPI). This provides detailed data allowing the shipowner or operator to make fact-based operational decisions.
An easy process
SHAPE is a simple and transparent process. Six key stages comprise the SHAPE measuring and monitoring system. First, the vessel’s individual speed power reference curves are established. This is followed by collecting in-service data which is then cleansed and purified to eliminate extreme operating conditions and the effects of environmental factors.
Next, a precise speed loss calculation is performed. This is a critical measure for understanding vessel performance and fuel efficiency as power increase and speed loss are directly related. From this, the four KPIs are calculated:
Dry docking performance – calculates the changes in hull and propeller performance over drydocking periods.
In service performance – calculates the effectiveness of the vessel’s hull and propeller solutions.
Maintenance trigger – calculates the change in hull and propeller performance over a given period between drydocking and in-service use.
Maintenance effect – calculates the change in hull and propeller performance before and after a maintenance event.
Following this indepth analysis, Hempel can offer solid, valuable technical advice to the ship operator, advising them on the operational decisions they can take to positively impact their fuel efficiency and ensure best practice in vessel maintenance.