Come September 28, Navy’s 1st aircraft carrier dry dock to start operation

The dry dock will be inaugurated by Defence Minister Rajnath Singh on September 28. (Express Photo by Pradip Das)

THE Naval dockyard in Mumbai is bustling with workers readying the place for the September 28 grand opening of the Navy s first aircraft carrier dry dock, designed to accommodate INS Vikramaditya.

The state-of-the-art dry dock, constructed over nine years at a cost of Rs 1,000 crore to cater to the repair, refuelling and maintenance of Navy ships, will be inaugurated by Defence Minister Rajnath Singh next week.

A dry dock is a berth where maintenance and repair works, which are not possible when the ship is in water, take place. It is flooded to allow the ship to enter the berth, after which the water is removed so that the works on it can be carried out.

The dimensions of the Navy s largest dry dock are 281-m long, 45-m wide and almost 17-m deep, designed chiefly for INS Vikramaditya. When INS Vikramaditya is not docked here, it can accommodate two smaller vessels.

The naval dockyard in Mumbai has three other dry docks Bombay Dock, Duncan dock and Cruiser Graving Dock all dating back at least 150 years. Vikramaditya could not dock at any of these facilities.

Naval officers said the construction of the dry dock stretched over 40 lakh man days. Around 8,000 metric tonne of steel forms the core of the project. If laid down as one inch rebars, this would stretch all the way from Mumbai to Srinagar, an officer said. The project also consumed 5 lakh metric tonne of concrete, which is one-and-a-half times of what was used in building the Bandra-Worli Sea Link.

The project also includes two wharves, adding about a kilometer of berthing space to the dockyard. The design, inspired by a Singapore dock, saves space on land because it is built into the sea. It has the sea on three sides, and only its head on land.

The project commissioned by the Director-General Naval Project, Mumbai, was awarded to Hindustan Construction Company (HCC) on April 12, 2010. HCC s contract was to build the dry dock and strengthen the north and south wharves. The design of the dry dock went through several rounds with engineering firm Royal Haskoning India. Officials said the design took about five years to be finalised.

The dry dock can hold up to 200 million litres of water more than 80 Olympic-sized swimming pools and the 1.5-m thick massive reinforced concrete dock floor can hold ships weighing up to 90,000 tonne. The dry dock has two equilibrium valves that can fill it up in 90 minutes each. It also has eight massive dewatering pumps that can empty a water tanker of about 10,000 litres in three seconds, removing water from the dock in about two-and-a-half hours.

Constructing the dock floor 300 m into the sea was an engineering challenge met by building a coffer dam to keep the sea water out, said an official. The coffer dam was built with 114 steel piles filled with reinforced concrete, each weighing 60 tonne and 170-m long concrete beam. The officer added, A team of workers worked night and day to remove a 2.23 lakh tonne of silt, enough to lay 90 football fields and 45,000 tonne of concrete debris, paving the way for the construction of the dock floor.

The first trial at the dock was conducted in June with INS Delhi docking in. On Thursday, INS Kolkata was docked in. Before this, we had to take Vikramaditya to the Cochin Shipyard for maintenance, said an officer.

Officers said that using private dry docking facilities meant that the Navy, too, queued up to avail dry docking facilities. It meant a huge burden estimated to be about Rs 10 lakh a day depending on the ship and the maintenance it needed on the exchequer.

Now the Navy will have control over how much time its ship will take to get repaired or serviced. This will have a huge impact on the turnaround time of ships coming out of the docks. Private facilities providing dry docks for a profit would not always give precedence to naval ships. Now that it has this new dry dock, this will make a great difference to its fleet of over 150 vessels, an officer said.

Unlike its predecessors, the dry dock will have mechanical arms running on rails along its length, from where every part of the ship will be easily accessible. The dry dock project also entailed a dock master complex, with a parking facility for 400 vehicles.