Abstract:
With the growth in pipeline installations all over the world, there is a great demand for highly
productive and robust welding systems. Mechanised pipe welding has been developed over the
last 50 years and the present focus is towards development of automated pipeline welding
systems. Pipeline welding automation is aimed at reducing costs and improving the installation
quality. To attain fully automated pipe welding systems there is a need to rely on sensors and
controls systems to mimic human like capabilities, such as visual inspection, in real time. The
key aim of this work is to develop and evaluate methods of automatic assessment of weld bead
shape and quality during narrow gap GMAW of transmission pipelines. This implies that the
measured bead profile will be assessed to determine whether the bead shape will cause defects
when the subsequent pass is deposited. Different approaches have been used to conquer the
challenge that is emulating human reasoning, all with different objectives in mind. In spite of
extensive literature research performed, very little information was found concerning the real
time determination and assessment of bead shape quality and none of it was reported to be
applied successfully to the pipeline industry. Despite the continuous development of laboratory
laser vision systems commercial ones have been on the market for decades, some specifically
developed for the welding application. Laser vision sensor systems provide surface profile
information, and are the only sensors which can satisfactorily measure bead profile on a narrow
groove. In order to be able to use them to automatically assess weld bead shape and quality, a
deep understanding of their characteristics and limitations needs to be achieved. Once that
knowledge was attained it was then applied to determine the best sensor configuration for this
purpose. After that the development of human like judgment algorithms were developed to
accomplish the aim that was set. Empirical rules were obtained from an experienced welder
regarding the acceptability of bead shapes and were then applied in the developed system with
good results. To scientifically evaluate and determine the rules to use in this system, further
experiments would be required. The output of the system developed showed very accurate,
reliable and consistent results that were true to the external measurements and comparisons
performed. The developed system has numerous applications in the pipeline industry and it
could easily be implemented on commercial systems.