Successful under extreme conditions

The North Sea Giant, with its two cranes, is one of the largest and most advanced ships ever built in this way. The huge ship is driven with five propellers from Voith Schneider. The North Sea Giant has a length of 161 meters and is designed with a width of 30 meters for extreme deployments in high seas. It is equipped with several crane systems and has a total capacity of nearly 1,000 tons. 

With a lifting capacity of 420 t, the SHS Tower Crane from AXTech in Molde, Norway, is a new tool for installing and maintaining subsea installations and technical equipment in the North Sea. TSUBAKI KABELSCHLEPP products contribute significantly to the safe function of the complex crane system, which is operated and maintained by TechnipFMC, a global leader in oil and gas projects. Due to the particularly massive construction and advanced technical equipment of the ship, the North Sea Giant is operational under extreme maritime conditions.

The ship's crane is designed so that it has a movement span of 180°. This allows heavy equipment and facilities up to 400 tons to be lifted from the deck of the ship into the sea. The transport is ensured with more than 15 hydraulic hoses which are filled to approximately 450 bar.

Due to the circular movement of the crane, it is necessary to guide the hose during movement to ensure a secure supply to the crane. And due to the extreme sea conditions during use with swinging loads in excess of 400 tons, the power supply to the crane is a critical interface in ensuring the function, and in particular, the safety of the entire facility.

Special engineering challenge

In order to achieve the maximum safety and service life for the crane, it was decided to use a cable carrier for routing the hoses. The system is to guarantee the power supply to the base of the crane, a few meters above the water level, at any time and under extreme weather conditions. Here, it is inevitable that the entire device will be regularly 100 % exposed to the salt water. The system must also guarantee the necessary stability required due to ship movements in rough seas.

With these technical parameters and operating conditions TSUBAKI KABELSCHLEPP was contacted, among others, as one of the leading companies in cable carriers, in order to get a complete solution. It became clear to AXTech in the selection process that in this extremely demanding, time-critical and also for AXTech at this time, unique project, that only TSUBAKI KABELSCHLEPP could meet this challenge - no other provider could provide a comparably convincing concept.

"We felt from the beginning that KABELSCHLEPP would be the right partner in this project in the area of engineering and solution competence. We immediately noticed that the KABELSCHLEPP Team absolutely wants to successfully implement this challenging project with us," said Andreas Ludvigsen, Lead Engineer – Mechanical Design at AXTech. 

When the cable carrier project planning was started, all construction space conditions of the existing and already partly made steel structure of the crane were already given. Due to this, the adaption of the entire design of the solid stainless steel cable carrier and the necessary supporting structure in close consultation with the customer was required.

Here, a complete solution was developed in close cooperation with the various technical departments and using 3D simulations, that met the limited construction space specifications and the extreme requirements.

Manufacturing and testing under maximum quality standards

The production of all parts was subject to maximum requirements to ensure the quality of parts. The safe and high-quality production of all components was controlled during production using a comprehensive inspection schedule.

Due to the particular environmental conditions and the possible dangers posed by a failure of the cable carrier, each screw was subject to a burden of proof of meeting the customer requirements and ensuring the quality requirements.

"The time frame was extremely tight and if I'm honest we had doubts about whether KABELSCHLEPP could really succeed - they showed us they could - a great performance" attested Torgeir Haubekø, Manager Project Department, the KABELSCHLEPP team.

Installation and commissioning

Through the experience gained during the test design of the facility, the requirement that TSUBAKI KABELSCHLEPP would be responsible for the safe installation and commissioning arose from the beginning. Due to the time line and the installation costs on board the ship, the shortening of the installation time from an estimated 15 days to a few days was requested.

The steel structure from TSUBAKI KABELSCHLEPP was created so that a possibility was established to pre-assemble the complete facility in an assembly hall in order to subsequently raise these segment parts onto the ship within the shortest possible amount of time and with only 3 lifts. Through this, the assembly time and the resulting costs were able to be drastically reduced.

The entire construction was subject to stringent safety precautions. Therefore, the stability and load carrying capacity of the system were tested in advance using modern calculation programs to ensure the safe lifting process from land to ship. Using a highly variable mounting system, the entire system was able to be installed on board the North Sea Giant quickly and safely and below the predetermined tolerance conditions.

The North Sea Giant has now been successfully at sea for 2 years with the new crane system and it is now attested: AXTech and Kabelschlepp - a successful partnership!