Pipe welding is an efficient, cost-effective way to join sections of pipe. The current methods for welding have existed for decades, but, with new technological advances, what new techniques will be developed in the future and how will they compare to existing methods?
The current, most common method for connecting pipelines is gas metal arc welding (GMAW). With this technique, an electric arc is produced that comes between the piece(s) of metal to be welded and a wire electrode. The result is an intense heat source that melts and welds metal. The welding gun also produces a gas that protects the process from contamination.
There are various iterations of the GMAW process, such as the use of different sources of power to weaken and soften metal. A consistent supply of DC and voltage is the preferred method of power for pipe welding equipment, but AC and constant current methods are available as well.
There are also options regarding how the metal is transferred, with the four main techniques being pulsed-spray, short-circuiting, spray and globular. Each method has its pros and cons, however.
A slightly slower welding method, but still common today, is shielded metal arc welding (SMAW). The process is the same a GMAW, but the electrode feed is not continuous. In total, there are several arc welding techniques that have their uses in industry, as well as other methods such as resistance, gas and energy beam welding.
GMAW is still considered the best option for most processes. Also, costs are predicted to be reduced greatly in the future with duel-tandem and root pass GMAW developments.
When it comes to maximising productivity, the attention has always been centred on one-shot welding. With this method, the welding time is shorter than GMAW. The problem, though, is that the welding needs to be carried out at one station. Also, there are post-welding procedures needed to finish the process and the important path operations may take longer to complete, due to a greater setup time.
At the moment, power beam welding is seeing more development than one-shot techniques due to there being fewer problems to overcome. The issues with one-shot methods arise because multi-head and multi-pass welding is not possible with this technique, whereas it is with beam welding.
Related to power beam welding, Nd:YAG is a type of laser that can be used to connect pipeline, but they are of more use in areas of fibre-optic beam delivery. In combination with GMAW, they have shown to be electrically inefficient and, therefore, of no use for pipeline construction. The problems of Nd:YAG are solved, however, with the latest laser technology, which is of a higher power in comparison. The efficiency issues are overcome and, as such, are more promising as a method for pipeline construction.
Overall, one-shot techniques using magnetically impelled arc butt (MIAB) and induction methods are the ultimate aim for pipeline welding, but there has been little success so far.
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