Installing winches and cable drums below deck in very limited space

SITUATION

Pioneering Spirit, the largest lifting ship in the world, owned by the Swiss offshore company Allseas, was built to remove, install and transport offshore platforms. For the Jacket Lift System (JLS), several winches and cable drums had to be installed at the rear of the ship, below deck. To achieve this, several, partly identical, displacement actions were required. 

CHALLENGE

A height restriction due to existing pipes and cables ensured that installation by using a crane or forklift was not an option. The only efficient and safe solution was to skid the winches and cable drums to the defined positions.  

In addition to the height restriction, there was a second challenge: various changes in direction (90 degrees) in the displacement route. This normally requires a lifting action and the complete relocation of the skidding system. In limited workspace, this is both complex and time consuming. The latter was particularly relevant, because the same displacement route had to be traveled several times with the different loads. Allseas was looking for a solution, in which this complex process could be completed several times safely and efficiently. The fewer steps, the better. 

SOLUTION

Holmatro has developed an extremely lightweight, fast and easy to set up skidding system that could be easily carried, handled and positioned by one or two persons without the need of a forklift or the use of extra equipment. The system has a capacity of 200 tons, based on 2 parallel tracks. The total construction height of the system section under the load is just 56 mm (2.20 inches).
 
The essence of a skidding system is that relatively little force is required to move a heavy load horizontally. The tracks are easy to connect to each other by a click system. With a handle on the push-pull unit, the push or pull direction of the lightweight Skidding System can be switched in a split of a second. The return line of the push-pull cylinders (each with a capacity of 10 tons) is integrated in the cylinder, which significantly reduces the chances of this being damaged.

In order to be able to carry out the multiple displacement actions and easily change direction, Holmatro has developed a special cross section, which enabled Allseas to carry out the work quickly and safely in the limited space. The installation plan of the skidding system required different track lengths. Holmatro designed 4 different lengths (1.8 m, 1.5 m, 1.1 m and 0.8 m), which were needed to carry out the 6 displacement actions. 

During the operation, several lifting actions had to be done. For this, Holmatro supplied several cylinders. These were operated with the same hydraulic pump, which was also used to control the skidding system. This ensured a smooth and efficient working situation. Partly due to the optimized design of the skidding and lifting system, Allseas was able to complete the displacement actions much faster than planned. 

Read more about Holmatro Skidding Systems