It is submerged arc equipment specially designed for welding in narrow places, particularly for the nuclear and very heavy petrochemical industry.
In wide thickness walls (greater than two inches) making a bevel for a welding arc implies a lot of time, as well as material waste. Also the use of consumables is greater when welding with a V bevel. For that reason this joints are prepare with J bevel.
That is why narrow gap headers were developed. The arc is identical to a traditional one with the only difference in the welding torch, being this very large and thin. It can enter in spaces of less than ¾ inches and up to 6 inches depth. With this besides time saving, the input and base material waste is reduced.
For very depth applications it requires a special tracking joint device, because the operator is not able to see in such a small space.