Dredgers

89.05 - Light-vessels, fire-floats, dredgers, floating cranes, and other vessels the navigability of which is subsidiary to their main function; floating docks; floating or submersible drilling or production platforms. - Dredgers 8905.20 - Floating or submersible drilling or production platforms 8905.90 - Other 8905.10 This heading covers : (A) Light-vessels, fire-floats, dredgers, floating cranes, and other vessels the navigability of which is subsidiary to their main function. These normally erform their main function in a stationary position. They include : light-vessels; drilflships; fire-floats; dredgers of all kinds (e.g., grab or suction dred ers); salvage ships for the recovery of sunken vessels; permanently moored air-sea rescue {oatsbathyscaphes; pontoons fitted with lifting or handling machines (e.g., derricks, cranes: grain elevators) and pontoons clearly designed to serve as a base for these machines. House-boats, laundry boats and floating mills are also covered by this group. (B) Floating docks. Floating docks are a type of floating workshop used instead of dry docks. They are generally sfructures of a U-section corn rising a platform and side-walls, and are equipped with umprng compartments which ena le them to be artly submerged to permit the entrance o vessels requiring repair. In some cases they may r3e towed. g P A further type of floating dock functions in a similar manner, but is self-propelled and e uip ed with powefil engines. These are used for the repair or transport of amphibious ve ic es or other craft. %. 7 (C) Floating or submersible drilling or production platforms. Such platforms are generally desi ed for the discovery or exploitation of off-shore depos~tsof oil or natural gas. Apart om the equipment required for drilling or roduction, such as derricks, cranes, pumps, cementing units, silos, etc., these platforms ave living quarters for the personnel. g R These platforms, which are towed or in some cases self- ropelled to the exploration or roduction site and are sometimes capable of being floate fiom one site to another, may e! divided into the following main groups : S (1) Self-elevating platforms which, apart. fiom the workin platform itself, are fitted with devices (hulls, caissons, etc.) wh~chenable them to oat, and with retractable legs which are lowered on the work site so that they are supported on the sea bed and raise the working platform above the water level. i? (2) Submersible latforms, the substructures of which are submerged over the work sites with their bal ast tanks resting on the sea bed in order to provide a hi degree of stability to the working platform which is kept above the water level. The allast tanks may have skirts or piles which penetrate more or less deeply into the sea bed. f' (3) Semi-submersible latforms which are similar to submersible latforms, but differ fran them in that t e submerged part does not rest on the sea ged. When working, these floating platforms are kept in a fixed position by anchor lines or by dynam~c positioning. E Fixed platforms used for the discovery or exploitation of off-shore deposits of oil or natural gas, which are neither floating nor submersible, are excluded from this heading (heading 84.30). This heading also excludes ferry-boats (headin 89.01), facto shi s for processing fishery products (heading 89.02), cable-laying ships and weather (heading %.06fl LPa -