Hull efficiency

Hull fouling and its effects on fuel efficiency have increasingly become central to the marine industry conversation. With fluctuating fuel prices, the IMO 2020 targets, the true effects of soft fouling like slime being recognised, and changing operational patterns (such as slow steaming and longer idle periods) now prevalent, the need to re-evaluate hull efficiency options has never been greater.

In this context, coating selection based on trading patterns and anticipated fouling has never been more important, because it helps to minimise operational expenses and the total cost of ownership (TCO). As a result, coating selection is increasingly an investment consideration, not just a capital expense.

Even so, some operators looking to minimize dry docking expenses without committing to hull performance investments are inadvertently increasing their operational cost by compromising on a more quick-fix solution – cleaning.

We recognise that hull cleaning may be a legitimate option when required by unexpected changes such as needing slow steam or idle in warm waters. However, it may be becoming a pattern for some operators, who are acting more on instinct than solid data. In fact, the boost in hull performance they are looking for would be better achieved by investing in a superior coating at the last drydocking.

Such a reactive approach may not be cost-effective or sustainable.

While cleaning has an immediate effect on removing fouling, some hull coating may also be removed or damaged, which reduces performance. Over time, this will have a cumulative impact on the smoothness of the hull, degrading the coating’s effectiveness and longevity and accelerating polishing.

If cleaning is required, at Hempel, we would recommend water jetting to achieve the desired results. Abrasive solutions would not only increase the cost but at the next dry dock more surface blasting would be needed as the coating would be scraped off and damaged.

The IMO is rightly concerned about sustainability challenges too. Invasive species transfer is a risk if an inappropriate hull coating is used. For vessels experiencing frequent long idling times, the risk grows.

And when a hull is brushed clean, what is removed is likely to enter the marine environment, a danger that even filtration or suction may not eliminate.

As a result, ports in Australia, New Zealand, California and many other parts of the world no longer permit fouled vessels to enter or hull cleaning to be done. In extreme conditions, this can mean vessels can find themselves stranded between ports.

In 2017, bulk carrier DL MARIGOLD found itself ejected from New Zealand waters because of biosecurity concerns about its hull, only to then be rejected by Fiji too, leaving the vessel in a maritime limbo.

At Hempel we strongly believe in prevention, not cure. The question of hull cleaning does not arise when a hull coating truly does its job and prevents fouling.

We design coatings to meet specific operational parameters and offer fouling protection throughout service lifetime, so that the downtime and harm of hull cleaning is avoided. An advanced system such as Hempaguard MaX, guarantees 1.2 per cent maximum speed loss over five years and new standards of idle time antifouling.

This is the fit-and-forget approach to hull performance optimisation, and the smart solution for optimum TCO.

Hempel has gained valuable insight into hull cleaning issues through its involvement in a hull cleaning working group within BIMCO, the world’s largest direct-membership organisation for shipowners, charterers, shipbrokers and agents.

The mathematics of hull cleaning