In 1984 Vickers Shipbuilding in Barrow enquired if F. Bode and Son Ltd could design and manufacture a bespoke set of welding and fabrication positioning equipment for the then new submarine project.
Before this date vessels around 6 metre diameter were the norm, and these submarines were nearly twice this size, so new techniques were required to manipulate 200 tonne parts, and rotate them accurately for welding.
Prior to these designs the traditional way of welding was with a Column and Boom that had a ‘Lay Trough’ attached to the Boom to which the welder had to lay down on his stomach to watch the welding arc. Health and safety laws now prevent this dangerous practice.
The welding process was also slow. Single or double welding wires would be used, using only 25 kg weld wire spools meaning constantly stopping to change the wire. Welding deposition rates were also low, leading to longer welding times.
Another issue for welding large diameter vessels is aligning them to give a straight length. Special methods of carrying out this process were needed as personnel could not undertake this alone.
Due to the immediate requirement in Germany for modern day wind tower manufacturing, Bode has taken their ‘know how’ from years of experience in providing fabrication equipment throughout Europe. The company have supplied many German companies and are associated with Ambau (all four works in Germany), SIAG (Germany, Czech Republic, and France), EEW (Germany), Steelwind (Germany), and Weserwind (Germany).
Bode immediately to used their experience and technology in improving the working designs. The use of welder platforms, Hydraulic Fit Up rotators, Crocodiles and long internal welding Booms, that would reach up inside the longest of vessels, were the answer for the new 60 metre Wind Tower Fabricators.
Using hydraulics, so called Crocodiles, and ‘Fit up’ rotators, the company can accommodate any diameter and weight of vessel which allows thick walled steel shells to be hydraulically pressed together. They are then tack welded, then fully welded together as they grow in length (Growing Lines)
The new method was to have a 14 m tall welders platform, with rear lifts to get the operator to the top, and for the welders to sit in comfort and safety many meters up off the floor. These platforms are capable welding longitudinal seams as well as circumferentially and of supporting many tonnes, and several 100 Kg drums of weld wire can be safely stored, so very few wire changes are required.
We also pay particular attention to operators’ safety, seeing that diameters are going up to 13 m and wall thicknesses 150 mm. A lot of time must be spent high off the ground, and safety harnesses are used while at the top.
There have further been advances in internal welding by the use of very long multi head booms, which can reach 26m down the inside of the vessel to perform Butt welds.
The increase in vessel diameters has further necessitated longer plates to roll into a circle. Therefore Bode has developed Flat Bed Butt welding rigs whereby sheets of 40m long and 3m wide can be firstly produced in the flat, then rolled to form a single shell and then welded via the Platform seam welding machine.
Increased welding speeds are needed in these very competitive markets. The twin welding wire method is slow due to low deposition.
UP Helfert have manufactured bespoke Pipe Mill Multi head Submerged Arc welding equipment for many years which was readily adaptable for the wind tower industry that demanded very fast welding speeds, with up to four and five welding heads.
Bode’s 4 wire welding heads can deposit up to 45 KG of wire per hour which is twice as fast as their competitors.