PD-50


PD-50, Soviet designation Project 7454, was a Russian large floating dry dock built at the Götaverken Arendal shipyard in Gothenburg, Sweden and commissioned in 1980s. At the time, it was the world's largest floating dry dock and used primarily to service the ships and submarines of the Northern Fleet.
The long and wide floating dock was owned by and stationed at Roslyakovo near Murmansk. In November 2018, the dock sank after a power outage while holding the Admiral Kuznetsov.

History

In March 1978, Götaverken Arendal shipyard in Gothenburg, Sweden was awarded a contract for the construction of the world's largest floating dry dock for the Soviet Union. While the company had previously built mainly oil tankers and bulk carriers, it was struggling for new orders after demand for one of its main product had dwindled following the 1973 oil crisis, and bidding for the dry dock was one of the attempts to diversify the shipyard's portfolio. With delivery time agreed as 18 months from signing the contract, the work was split between two shipyards in order to speed up the construction: Götaverken Arendal would build five of the seven sections while the nearby Eriksbergs Mekaniska Verkstad would supply the remaining two parts, and the sections would be joined together afloat using underwater welding. The floating dock was named PD-50 ; "PD" being short for "Plavuchiy Dok".
In August 1979, the nearly-finished PD-50 was towed to open sea for trials. During the final test, which involved finding out how fast the submerged dock could be deballasted, two ballast water tanks partially collapsed due to underpressure. The floating dry dock was hastily towed back to Arendal with visible denting on the shell plating and the shipyard workers scrambled to fix the damage. The repairs were completed in early September and PD-50 was handed over to the customer.
On 22 September 1979, PD-50 began its delivery voyage to Murmansk under tow by two Dutch tugboats, Smit Rotterdam and Smit London. On 3 October, after sailing around the Norwegian coast, the floating dry dock broke free in a storm and was blown ashore on the Soviet side of the Norwegian border. The grounding of the brightly-illuminated PD-50 was witnessed by Soviet border guards who later described the incident as if a small city had appeared from the sea and, only to be driven on the rocks by the storm.
While the damage to the grounded dry dock was extensive, PD-50 was deemed repairable. After refloating, it was towed first to Kirkenes and later to a shipyard in Stord. The repairs included lifting PD-50 fully out from water using pontoons and replacing 4,000tonnes of steel. In September 1980, one year after the grounding, PD-50 finally reached Murmansk.
On 29 December 2011, Russian Delta IV-class nuclear submarine caught fire while being docked in PD-50. The fire was extinguished by partially submerging PD-50 twice while K-84 was atop it.
In 2013, the Russian oil company Rosneft took over Shipyard No. 82 and its assets, including PD-50, in preparation of turning the old naval shipyard into a base for the company's Arctic operations. This has caused an outrage in the naval circles as the shipyard was one of the few in Russia with facilities capable of docking the country's largest surface vessels.
On 30 October 2018, Russian aircraft carrier was damaged when PD-50 suddenly sank under it, and one of the dock's 70-ton cranes crashed onto the ship's flight deck. One shipyard worker went missing and four others required medical attention, one of whom later died in hospital.

Replacement

In July 2019, Zvezdochka Ship Repair Center JSC and St. Petersburg company Investments Engineering Construction signed a contract for reconstruction and modernization of the Shipyard No. 35 located in Murmansk. As part of the RUB20 billion deal, two adjacent dry docks at the plant will be merged into one joint dock by a demolition of a partition between them and walls, slipways and other dock equipment will be modernized. After the modernization, it will be the largest dry dock in Russia, capable of docking Russia's sole aircraft carrier Admiral Kuznetsov as well as other country's largest vessels, such as the battlecruiser. As of December 2019, the work on reconstruction of the shipyard was underway.