Mechanized Underwater Welding and Cutting Techniques for VLFS
A0110Yoji Ogawa Organization National Institute of Advanced Industrial Science and Technology (AIST)
Mechanized underwater welding and cutting techniques are very
important for actual usage of very large floating structrures (VLFS).
In the case of construction, offshore welding plays a major part of
construction process. The total weld line is very long and a half
part is submerged under water. Water curtain type wet underwater
welding technique had shown its excellent ability for the construction
of a Mega-float which was carried out by the Technology Research
Association of Mega-float. A mechanized underwater welding machine in
over head position was also developed for maintenace of the Mega-float.
A kind of public facilities like offshore airport requires frequent
maintenance and alterlation to catch up the latest needs. Therefore
underwater mechanized cutting technique for alterlation and
dismantling has developed. At the final stage of the Mega-Float
project, we had dismantled the whole structure into eleven small units
to reconstruct another usage. In case of alteration, quality and
operating cost of cutting are very important. Therefore, we used
mechanized underwater flame cutting. Total length of underwater flame
cutting was more than 1000 meters. High quality cut was obtained
under sever condition such as heavy attachment of bio-fouling on the
bottom. This paper describes general aspect of mechanized underwater
welding and cutting techniques for an actual VLFS.