Coating selection process for Gulf Stream hydroturbines

2001

Biofouling, 2010

Biofouling, 2003

Protection against biofouling is essential for efficient operation of boats and ships. Restrictions on the use of traditional, toxic antifouling coatings call for new less toxic methods. Future antifouling strategies will likely be based on more specific action against dominant foulers and will require more detailed information about spatial and temporal differences in fouling communities on artificial substrates. In this study, the recruitment and succession of fouling organisms was examined on artificial (PMMA) panels exposed to natural flow speeds on the Skagerrak coast (Sweden). The recruitment of foulers on static panels was then compared to fouling allowed to develop on boat hulls in surveys of new nontoxic coatings. The temporal and spatial variation in recruitment was examined on a monthly interval within the boating season, from May-September. Furthermore, the succession of the fouling community was examined during the same interval. A total of 12 sessile invertebrate species was recorded on the static panels with dominant foulers being the barnacle Balanus improvisus (July-September) and the mussel Mytilus edulis (June-August). The mean abundance during peak settlement on panels after 1 month's deployment was 370+134 individuals dm 72 for B. improvisus and 340+415 individuals dm 72 for M. edulis. The succession of foulers on the panels led to a dominance of M. edulis (maximum of 7470+2830 individuals dm 72 ) over B. improvisus (maximum of 2295+680 individuals dm 72 ). This was in contrast to the fouling development on boat hulls, examined after 4 months exposure in 3 successive years, where B. improvisus was the dominant species (mean abundance 222+104 and maximum 713+527 individuals dm 72 ). Some boats were covered to an extent of almost 100% by B. improvisus with only a few M. edulis (mean abundance 20+16). The biomass of fouling on boat hulls varied from average dry weights of 1.3+1 to 13+5 g dm 72 . These results show that extrapolation from static panels (common in evaluation of antifouling performance) to fouling on boat hulls may be problematic.

As part of the Dutch Top consortia for Knowledge and Innovation (TKI) project 'Re-Drag with Nature' an inventory was made of the strategies that sea weeds apply to reduce the settlement and development of fouling organisms on their surface. This inventory was made based upon available literature and the results were assessed for their potency to protect man-made structures against biofouling. The reason for the focus on seaweeds was initiated by the observations that fouling pressure on seaweeds is in general low, and further supported by the knowledge that a lot of effort is currently being made to cultivate seaweeds and to utilise the compounds that can be extracted from it. However, the inventory was not fully limited to seaweeds. Where it inspired the thinking of new alternatives these were also briefly assessed. Seaweeds make use of physical and chemical strategies to keep their surface free of biofouling organisms. The physical strategies are based on the continuous renewal of surface material and are, therefore, not considered applicable to protect man-made structures without continuous maintenance. Self-polishing coatings are available for ship hulls, but these are only effective in combination with biocides. An alternative physical process that is not applied by seaweeds, but that may have the potency to reduce fouling is a combination of flow velocity and surface structure that could prevent early stages of fouling organisms from attaching to a surface. As this requires a controlled environment, it is not applicable to ship hulls or maritime infrastructure. It could work in industrial cooling water systems, but as the current methods that are applied there seem to fulfil the needs of the industry, this option was not further investigated. The chemical anti-fouling strategies of seaweeds are based on the production of a broad range of metabolites with the potential to reduce settlement and/or development of fouling organisms. Although the effectiveness of several of these metabolites has been shown on experimental scale, commercial application of bio-based compounds for anti-fouling purposes does not seem attractive, due to the high costs that are related with legislation/registration procedures for new chemicals. Apart from producing anti-fouling metabolites themselves, seaweeds can also support specific microbes that have little or no negative impact on their condition, but that prevent the settlement of more harmful species. A similar strategy, where a fouling species with low negative impact is favoured and supported, can have potential to manage fouling in an environmental friendly way on man-made surfaces where some drag is acceptable. As far as we are aware this is a completely new approach to deal with biofouling. When writing this report a proposal for a joint industry project (JIP) is being prepared that aims to investigate the potency of this approach to manage bio-fouling on offshore infrastructure.

This standard is issued under the fixed designation D4939; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval. 4

Biofouling, 2020

Today, ship hull fouling is managed through fouling-control coatings, complemented with inwater cleaning. During cleaning, coating damage and wear must be avoided, for maximum coating lifetime and reduced antifoulant release. When possible, cleaning should target early stages of fouling, using minimal forces. However, such forces, and their effects on coatings, have not yet been fully quantified. In this one-year study, minimal cleaning forces were determined using a newly-designed immersed waterjet. The results show that bi-monthly/monthly cleaning, with maximum wall shear stress up to $1.3 kPa and jet stagnation pressure $0.17 MPa, did not appear to cause damage or wear on either the biocidal antifouling (AF) or the biocide-free foul-release (FR) coatings. The AF coating required bimonthly cleanings to keep fouling to incipient slime (time-averaged results), while the FR coating had a similar fouling level even without cleaning. The reported forces may be used in matching cleaning parameters to the adhesion strength of the early stages of fouling.

Biofouling, 2017

When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent macrofouling growth in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds approximately 0.01 Pa. This value is found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.

Biofouling, 2000

Little is known about the performance of foulingrelease coatings at different geographical locations. An investigation was designed to measure the differences in biofouling and biofouling adhesion strength on three known silicone formulations and an epoxy control at seven static immersion sites located in California, Florida, Hawaii, Hong Kong, India, Italy and Singapore. The study found that whilst the relative performance of the coatings was similar at each site, there were statistically significant differences in the type and intensity of fouling that developed on the coatings and in barnacle adhesion strength among sites. The results emphasize the importance of evaluating potential coatings at more than one static immersion site.

2001

When marine fouling organisms attach to a ship, they create an uneven surface on the hull and increase the drag on it. Coatings are used to help minimize drag by keeping ship hulls free of fouling. Most antifouling coatings on ship hulls contain biocides and release them to control fouling settlement. Foul release coatings (FRCs) work differently, by preventing the settlement of the fouling by providing a low-friction, ultra-smooth surface onto which organisms have great difficulty attaching. Because FRCs are developed on the basis of an entirely different method for controlling fouling, it is helpful to understand this method to study their effectiveness. This article focuses on 2 issues relevant to drag and FRCs. It first discusses the preliminary findings from towing tests conducted to study the relationship of smoothness of the surface to drag on ships coated with FRCs. It then discusses the effects of slime fouling on drag on FRCs and self-polishing co-polymers. Observations ab...