Browsing by Author "Madhu, Joshi"

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    Antifouling paint schemes for green ships
    (Ocean Engineering, 2019) Mukherjee, A.; Madhu, Joshi; Misra, S. C.; Ramesh, U. S.
    Recent advances in antifouling (AF) paints in general prevent fouling in about 95% of the vessel's immersed surface. However the remaining area which amounts to 5% or less of the total area does get fouled. Although this level of fouling has marginal impact on the routine performance of the vessel it is a predominant vector for the transmigration of invasive species which is now a serious environmental concern. Virtually all ocean going vessels are coated with antifouling paints predominant among them are “Self polishing coatings”. CFD analysis conducted on various types of vessels have indicated that there are certain “hotspots” where the polishing rates are exceedingly high and would polish the AF paints at a much faster rate and ultimately result in the failure of the AF coating. A possible solution to this issue is to first identify these hotspots and suitable paint schemes/formulations are to be applied in such areas. An experimental procedure utilizing a “drum-test” apparatus can be used to compute the coating thicknesses based on wall shear stresses. Such painting schemes would prevent the premature failure of the AF coating in general and significantly reduce the risk of transmigration of invasive species in particular.
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    Control of bio corrosion to prevent the propagation of invasive species
    (National Corrosion Council of India (NCCI), 2010-09-16) Madhu, Joshi; Mukherjee, A.; Misra, S. C.; Ramesh, U. S.
    Biocorrosion or biofouling on ships hull occursdue to the attachment of barnacles, mollusks and other aquatic organisms on the surface of ships which leads to increase in fuel consumption, reduction of the vessels speed, premature failure of the hull, etc. Recent developments in antifouling paints, in general, prevent fouling in about 95% percent of the vessels underwater surface, which ship operators find satisfactory as far as the routine vessel operation is concerned. However, this is not sufficient to prevent the transport or invasion of alien species. In recent years the issue of invasive marine species has been receiving considerable attention due to the fact that introduction of nonidegenous species or non-native species transmigrated from other areas to coastal waters often results in the reduction and even extinction of the native species and thereby severely disrupting the natural marine ecosystems. The predominant vector for the transport of nonindigenous species in marine environments has been shipping. While ballast water receives the most attention, hull fouling is now considered to be the most significant means for translocation of these organisms. For example, 90 percent of the 343 marine alien species in Hawaii are thought to have arrived through hull fouling. Certain niche areas of the vessel such as bow thrusters, sea chest, stern tube, rudder etc. are the likely areas to be heavily fouled. In addition, the other areas that are likely to be fouled are on locations where antifouling paint has been worn of due to excessive shear and bending of the hull. This paper reviews the various antifouling strategies and aims identify areas on the hull surfaces of certain classes of vessels that are prone to fouling by excessive shear and bending and identify suitable antifouling treatments to further reduce the risk of transportation of alien species.