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December 8, 2014

Dry dock for big ships like INS Viraat to be ready by mid-2016

In another two years, Mumbai might finally have a dry dock large enough for the repair and refitting of warships like INS Vikramaditya and INS Viraat at the naval dockyard. A senior navy officer said that the construction has been going on for many years now and is in its advanced stages.
As the term 'dry dock' suggests, it is a place where a ship can be docked and water can be drained out so repairs can be made in dry conditions. This method is particularly used when a ship's hull is to be surveyed and repaired.
While the city has other dry docks, none are big enough to accommodate large ships. At the moment, the INS Viraat, being a big warship, has to sail all the way to Cochin Shipyard Ltd. for repair and refit. Similarly, even the INS Vikramaditya's first repair and refit is scheduled to happen at this shipyard due to the unavailability of a dry dock to accommodate a warship of its size. The INS Vikramaditya is 283.5 metres or 930 feet long, whereas the INS Viraat is 226.5 metres or 743 feet long.
On April 12, 2010, the Hindustan Construction Company (HCC) was awarded the contract to build a new dry dock as well as north and south wharves (a structure on the shore of a harbour or river bank where ships can be docked). At that time, the cost of the project was Rs 608.39 crore, and the deadline for completion was April 2014 (48 months).
There are plans to test the strength of the retaining walls constructed by de-watering the dry dock area. This is likely to be carried out in February next year. If the result is favourable, further construction work will be carried out to complete the project that is already behind schedule. The scope of work includes earthwork, diaphragm walls, cofferdam, underwater concreting, dock walls, pumping systems, diesel tanks and ventilation system and also sub-station, emergency gen-sets etc. The permanent dock systems include caisson gates, dock-arm, hauling-in systems, cargo lifts, capstans etc.
The navy officer added that one of the key factors that will be observed is strength of the walls of the dry dock. If positive, there is likelihood of the project to get over in mid-2016. Once ready, it will enable various kinds of repair and refit work which varies from Short Refit to Medium Refit-cum-Midlife Update.
The dry dock at the naval dockyard was being constructed over 14 years ago for INS Viraat, but had collapsed on June 7, 2000. The wall of the dry dock had collapsed while a de-watering operation was being carried out to test the structure. This dock was made at a cost of over Rs 700 crore. The dock was made up of several blocks. While de-watering, silt began to seep in, followed by water. However, the design of the new dry dock is a single block to prevent any kind of seepage.

DNA
 

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