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AFDB Floating Drydocks [Plavuchiy Dok]

During the life cycle of the vessel or any craft, the need for its maintenance and repair is repeatedly encountered. An integral and most time-consuming part of these works are inspections, cleaning from algae and seashells, painting, and also repairing the underwater part of the ship's hull and its bottom-sided fittings. To begin such work, it is necessary to drain the underwater part of the hull.

Ship repair and shipbuilding enterprises use various lifting and release mechanisms, ship lifting facilities and facilities for launching and lifting ships and watercrafts: slipways, slips, dry, loading and floating docks, vertical ship lifters. For installation, inspection, inspection, repair and maintenance of submersible, rowing, steering and thruster mechanisms, stern shaft seals, outboard fittings, the underwater part of the hull, the vessel must be lifted out of the water or have dry areas during its laying and construction.

According to historical information, the priority in creating this type of structure belongs to Russia. The first lifting of the ship by the SPS, in which the hull of the captured ship Camel was used, was carried out in the Kronstadt region during the reign of Peter I. Instead of the cut off stern tip Sasha! And its removed decks, a waterproof shutter was installed the ship and the pumping of water from the resulting basin allowed to drain the underwater part of the ship. Structures of this type for a considerable period of time, both in our country and abroad, were called chambers, regardless of their design features and purpose. Only in the 19th century, the term floating dock was used, floating SPS acquired the traditional appearance, a pontoon with two towers.

The priority in the creation of such lifting structures belongs to lies in Germany, where the first of them was built at the beginning of the 20th century, and the largest number was built during the first and second world wars. Such ship-raising structures have found application with a significant load of ship-repair enterprises by docking repairs of the same type vessels. The number of dock pontoons for one dock uterus reached 8 units. The presence of one complex structure and several simplified components in the form of dock-pontoons as part of the floating dock complex allowed to significantly reduce not only the cost of creation, but also the operation of the entire ship-lifting complex per one berth.

A Dry (pumped out) dock is a stationary structure (pool) for docking below the level of the surrounding water area. A dry dock consists of three main elements: Chambers with watertight sides and bottom, where the docked ship enters the vessel when it is filled with water; The shutter, by which the chamber is separated from the water when it is drained; and Mechanical and lifting equipment. One of the most important parts of the dry dock is the gate of the entrance part for ensuring water tightness, quick opening and closing of the internal water basin, possibility of repairing the dock structure without decommissioning.

A Flooding dock is a building-launching structure with a deep-water channel for the input and output of ships, intended for their repair and construction, similar in design to the loading chamber, is one of the varieties of the dry dock. The main structural difference lies in the device dock camera, which allows simultaneous installation of two or more ships across the width and not on the bottom of the chamber, but on the berth platforms located along the dock walls above the maximum water level in the open water basin.

The construction of such docks is most expedient in the seas with large fluctuations in level due to frequent tides. The entry of the documented ships is carried out at the moment of high water, and the dock is drained at the moment of low water, which significantly reduces the operating time of the drainage pumping units. The ships are entered into the chamber, separated from the water area by the sluice gates system, through the deep-water channel located between the slipways, with the shutter open, then it is closed, the chamber is filled with water to a level that will ensure the ship's movement to the slipway.

A floating dock is a mobile non-propelled or self-propelled floating structure of a technical fleet, equipped with lifting and transport equipment, mechanisms for flooding and lifting, devices for entering the vessel, installing it on keel and zygomatic blocks, water, gas, steam, compressed air and electric power systems.

The floating dock consists of pontoons, on which a vessel lifted from the water is installed, and side towers. Pontoons and towers of floating docks can be composed of several sections. According to the number of sections, floating docks are divided into monolithic (one-section), in which the pontoon and the towers represent a solid structure, and sectional (composite), consisting of two, three or more sections. There are large floating docks of seven and even ten sections. Naturally, with an increase in the number of sections, the capacity of the dock increases, for example, to 100,000 tons (ten-section dock). Floating docks are steel or reinforced concrete and composite. At present, reinforced concrete docks are being widely constructed, which makes it possible to reduce the consumption of metal for construction by 5060%, and the cost of construction by 2030% compared to steel dock. Reinforced concrete docks do not require regular self-docking for cleaning, painting and repairing the underwater part of the hull. In recent years, a number of docks with reinforced concrete pontoons and steel towers have been built.

Monolithic (one-section) docks are equipped with one continuous pontoon, which forms a seamless structure with continuous towers fixed on its sides. Its disadvantage is the impossibility of self-contained. Sectional (composite) docks (sectional docks) consist of several monolithic sections, each of which is able to function independently. The length of each pontoon is less than the width between the towers, which ensures self-docking, but its longitudinal stability and longitudinal rigidity are smaller than those of a monolithic dock structure.

Docks are divided into repair, transmission, transport, cargo and multipurpose semi-submersible ship-docks:

  • repair with developed means of mechanization, welding, gas cutting, sandblasting, grinding, painting equipment
  • transfer (reloading, transfer, launch) for lifting the floating object out of the water and transferring it to a dry horizontal slipway or finishing descent from it to the water after construction, reconstruction or repair; equipped with rail tracks with mobile trolleys, clamps for precise docking with coastal berths of factories and mechanisms for maneuvering, positioning and inclining
  • transport vehicles with a minimum set of steering devices and propulsive devices for navigating watercraft over water areas with shallow depths or difficult maritime conditions
  • cargo for water delivery of very large, heavy prefabricated elements of building structures
  • multipurpose semi-submersible heavy-lift vessels (SSHLV), dock-ships with huge open, flat cargo decks have a large carrying capacity (deadweight over 117 thousand DWT), are completely autonomous and highly automated for the following activities: performance of cargo and transport functions for the rapid delivery by sea of massive and dimensional building structures, floating port cranes in the collection, offshore drilling and production platforms, decommissioned, faulty or unfinished military and civilian ship raising (ship raising, salvaging) - rescue operations for lifting aboard, sunken and submerged watercraft

Double-deck floating docks were widely used and widely used at ship-repair enterprises of the marine fleet and fisheries. The hull of this dock consists of a pontoon, on the sides of which towers were erected. They are the main links that ensure the longitudinal strength of the dock. The upper plane of the pontoon forms a slipway, on which kilta blocks are installed in the center plane, and side panels at sidewalls at a distance of 1.0-1.5 m. , 5-2.0 m) between the ships side and the inner wall of the tower. The length of the dock may be less than the length of the documented vessel by 10-15%. The upper horizontal platforms of the towers are called top-decks. The width of the towers on the top-deck make 3-4 meters.

Inside the towers there are drainage pumps, service and living quarters for the docking crew, workshops. Crane equipment is usually placed on the top deck for supplying cladding sheets or assemblies to the vessel being repaired. The towers have bevels at the ends, which make it possible to increase the illumination of the vessel being repaired in the dock and reduce the wind load when towing the dock. This kind of floating dock (as opposed to single-turret) has good stability. The height of the towers above the slipway depends on the maximum draft of ships accepted by the dock. When docking, the vessel must freely pass over keel blocks, for which a gap of 0.30.5 m is provided between the bottom of the vessel and the upper edge of the keel blocks with the shipboard docked. Dock pontoons are designed on the basis of the condition that their buoyancy exceeds the mass of the dock with its equipment and the weight of the vessel being raised to the dock. In this case, the slipway in the raised state should rise above the water level by 0.20.8 m. Inside the pontoons of the dock, they are divided into several compartments by longitudinal bulkheads. The pontoons and towers have transverse watertight bulkheads that divide the pontoons and towers into a series of wet and dry compartments. Wet compartments are used to receive ballast water, dry - to accommodate the dock devices and mechanisms.

Floating docks are provided with flooding devices and powerful means for draining ballast compartments. Pontoons are flooded by gravity through the Kingston, the opening and closing of which is carried out from the control post, located in the wheelhouse on the top deck. From the same post, the drainage pumps are controlled to remove water from the ballast compartments. Docks have drainage pumps (with a capacity of about 5% of dewatering capacity), which are designed for stripping compartments and leveling the roll and trim of the dock during flooding and lifting. Floating docks are also systems of steam (or water) heating, drinking and washing water and fire.

Vertical ship elevators (boat lift, ship-lift system) are lifting and lowering devices with a cargo platform installed between two pile piers, equipped with rail tracks with sliding carriages, lifting mechanisms on both sides, which, according to their operating principle, are divided into electromechanical, hydraulic, pontoon and combined; serve for raising from water and back descent of watercraft, concrete caissons and bataports for carrying out dry dock activities. The weight of the ship elevator ranges from 3000 tons to tens of thousands of tons. Vertical movement of the platform with a raised vessel is carried out by lifting mechanisms. On the rail tracks laid on the platform, the lifted ship on the slip carts is rolled in to the repair site at the shore berth platforms of the shipyard.




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Page last modified: 18-12-2018 18:43:26 ZULU