An Introduction to Orbital Welding

Orbital welding is a mechanised version of the tungsten inert gas arc welding (TIG) process and is used to weld stationary tube or pipe; the tungsten electrode contained in the weld head rotor rotates or “orbits” around the weld joint circumference.

The TIG process can be either a fusion (autogenous) process in which the edges of the weld joint are heated by the arc and fused together without the addition of filler material to the weld pool. Or filler, usually in the form of a solid wire can be added. The choice of autogenous or wire feed is dependent on a number of factors such as: material, wall thickness, application, and acceptance criteria.

In a typical fusion application the tube or pipe would have a thin, regular wall (typically less than 3mm), the material would be suitable for welding without the use of a filler (such as Austenitic Stainless Steel or Titanium) and the weld acceptance criteria requires a good visual profile and surface finish such as that required in the semiconductor and pharmaceutical industries. Other industries such as aerospace and offshore also utilise the fusion technique.

The OSK range of Orbitec weld heads are fully enclosed and are designed for fusion welding of thin walled pipe and tube, the weld heads come in a number of sizes and configurations covering tube diameters ranging from 3mm (≈1/8”) to 115mm (≈4.500”).

In a typical wire feed application the pipe would have a heavier wall thickness, materials less suitable for fusion welding such as Cr Mo, Inconel etc. can be welded because the filler materials used are designed to assist and complement the welding process. Weld acceptance criteria is biased more towards strength and reinforcement of the weldment, typically wire feed is more widely used in the petrochemical, power generation, and nuclear industries.

The OSW & OSZ range of Orbitec weld heads are the open frame type, these can be used for fusion applications where the weld finish criteria is less stringent, they can also be used in conjunction with a wire feeder to add wire and so complete welds with wall thickness up to 15mm thick.