Sector:

  • Ports & Shipyards

Expertise:

  • Heavy lifting

  • Jacking

Benefits:

  • Record breaker

  • Optimized schedule

  • Increased safety

Location:

  • Russian Federation

Battling the Barents Sea to raise the Kursk. The Kursk hit the seabed 108 meters below, driving its bow 2 meters deep into the clay.

On August 12, 2000, during an exercise in the Barents Sea, the Soviet nuclear submarine Kursk was rocked by two devastating explosions, the second of which measured 3.5 on the Richter Scale. 

One of the largest, newest and finest in the Russian fleet, the Oscar Class 2 nuclear submarine plummeted to the seabed together with her precious crew of 118 navy personnel. In the days that followed, efforts to reach and rescue the crew unfortunately failed, and all the men on board were lost. The Kursk would remain at icy depths of 108 meters for the next 14 months before an international team was assembled to bring the Kursk home.

Kursk before tragedy

The Kursk, measuring 115 meters long and weighing 24,000 metric tons, was badly damaged when torpedoes onboard the submarine detonated and blasted a hole through the bow. This enormous submarine, immobilized upon the seabed, still contained two nuclear reactors and 24 missiles, as well as an unknown number of live torpedoes in the bow.

The rescuers must contend with the threat of unexploded weapons, possible radiation and unknown structural integrity to raise the Kursk. And all of this must take place 108 meters below sea level in one of the world’s most hostile bodies of water, the perilous Barents Sea on the edge of the Arctic Ocean, 250 kilometers off the coast of Norway. Impassable in the winter months due to high winds and icy conditions, there would only be a narrow window in which the lift could take place.

Back in the Netherlands, a team of 100 technicians, computer programmers and engineers began on designing and building the 3,000 ton of cutting and lifting equipment that would be needed to raise the Kursk. The team would have just five months from initial preparations to actual lift.

Within a 3-month period, over 3,000 tons of tailor-made equipment was designed, fabricated, installed, and commissioned onto a barge which was mobilized to the Barents Sea in August. The safest way to lift the Kursk would be to remove the damaged bow section. Mammoet’s team designed a robotic cutting wire that would provide the precision and force needed to remove the front section in the underwater environment.

Consisting of a steel thread with a specially processed buffer, the cutting wire was positioned between two suction anchors and moved hydraulically between the anchors as they sucked themselves deeper into the seabed.

Meanwhile, in Rotterdam, the Netherlands, another team began to prepare an enormous barge with the lifting equipment needed to raise the remainder of the submarine. 26 strand jacks, each with a hydraulic lifting capacity of 900 ton, were assembled on the Giant 4 barge. Each strand jack was fitted with purpose-built grippers, attached to 200-kilometer cables, wound around purpose-built steel wheels. Each gripper would be inserted through a small hole and then opened to fix to the surrounding area, providing a strong anchor to the vessel. The strand jacks would then be used to synchronize all points of contact, compensating to ensure a level and controlled rise.

The 130-meter semi-submersible barge was specially adapted for use. A large hole was cut in the hull and large saddles constructed under the barge to transport the precious cargo underneath, with the Kursk’s command tower protruding into the hull.

After two months of engineering and construction, the barge with cutting equipment left for Norway, arriving in the port of Kirkenes in August 2001, shortly followed by Giant 4 with the integrated lifting equipment.

A team of specialist divers from Scotland, experienced in complex engineering projects in the North Sea, was hired to prepare the hull for the lift. 26 holes were cut with an abrasive jet of high-pressure water mixed with sand in both the outer and inner hull so that grippers could be placed inside the vessel.

Each gripper was joined to a strand jack and hydraulically operated, using remote onboard technology. Only once all grippers were in place could strand jacks lift the Kursk.

Each diver had to work a six-hour shift every 24 hours, spending the rest of the time resting in a pressurized tank on the dive ship. For 28 days, the divers would remain working, eating and sleeping at the same pressure as the seabed 108 meters below the surface.

After several weeks of hard work, the holes were ready and the divers guided the cutting tool into place. The cut site was very close to the chamber containing the remaining torpedoes so the positioning of the saw was important, a wrong placement could have set off another explosion and risked the lives of the dive crew. Several days later the cutting wire released the damaged bow from the rest of the Kursk.

Finally, Giant 4 moved into place above the Kursk ready to lower the grippers and begin the lift. But just as the maneuver was about to begin, the winter winds started raging. Although the strand jacks were each fitted with heave compensators, these could only steady the cables against a swell of eight feet.

The Giant’s captain needed to make a call: stay in place and wait for clear weather to come or head for shore and forfeit the operation.

The crew decided to stay, all equipment was secured on deck and the Giant 4 rode out the storm. After two days, the seas calmed, the Giant 4 lowered the strand jacks and the divers secured the grippers into the holes.

At 03:45 on 8 October 2001 the lift began. 9,000 tons of traction was needed to pull the Kursk from the seabed, combatting the suction of the mud surrounding it. Each connection point was independently and continuously compensated, and the carefully controlled ascent began.

At 15:00, a little more than 11 hours later, the Kursk was secured underneath Giant 4, ready for its final voyage home.

The Giant 4 and Kursk combined were towed into the dry dock at the port of Murmansk in the far North-East of Russia.

The dock was too shallow to receive the Giant 4 with the Kursk cradled underneath, so the same Russian engineers who designed the Kursk constructed two pontoons to lift the Giant 4 six meters above sea level. The Kursk rose and became visible above the water for the first time in over a year.

The Kursk was carefully transferred from the Giant 4 into the harbor but before the crew left, they spent time with the Russian Navy honoring the 118 men who made their final journey home. A poignant reminder of the immense responsibility of this salvage mission.

This operation was no doubt a risky one, harsh conditions and a dangerous cargo added significant challenges. The most important focuses were on the safety of the salvage crew and the protection of the marine environment. An independent team of British and Belgian radiologists was present throughout the salvage, protecting the crew and measuring equipment for radiation. No radiation leakage was detected and every recorded level well was within the permitted levels of background radiation.

In just five months, the Kursk was recovered and brought safely back to port. A President’s promise fulfilled by creative engineering in a race against time.

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