Orbital welding
[2] Rodrick Rohrberg of North American Aviation invented the orbital welding process to address fuel and hydraulic fluids leaking in and around the plumbing of the X-15 Rocket Research plane.
In order to have complete control over the weld pool, a perfect balance must be maintained between gravitational force and surface tension at every position of the torch.
Training and experience are required for an operator to be successful at consistently producing acceptable, repeatable, high-precision welds that meet today's standards.
Typically only 316L stainless steel tubing (not pipe) and fittings are used for automatic orbital welding and are obtained from a number of specialty manufacturers.
Automatic Orbital GTA welding has become the standard joining method for high integrity gas and liquid systems used in the Semiconductor and Pharmaceutical manufacturing industries.
An entire specialty industry supplying valves, fittings, regulators, gauges and other components for orbital welding and use in high purity applications has developed since the mid 1980s.
Orbital welding has almost always exclusively been carried out by the Tungsten Inert Gas (TIG / GTAW) technique using non-consumable electrodes, with additional cold-wire feed where necessary.
Carried out in an inert atmosphere, this controlled technique produces results that are extremely clean, have low particle counts and are free from unwanted spatter.
A flexible hose system is used to supply the welding head with power, inert gas, cooling water and filler wire where required.
In order to create high-quality weld seams it is essential that tube ends are carefully prepared with the edges of the workpieces being free of scale and impurities.
Owing to its ability to realise high-purity results, orbital welding found its place in the production of clean-room components for the semiconductor industry.
The construction materials used must be able to withstand the enormous mechanical loads produced by the high pressures and temperatures created by the media carried in the tubes.
Notches, pores and inclusions in the weld seams must be avoided at all costs, as these create weak points that can lead to subsequent formation of cracks.
One manufacturer has developed an orbital narrow gap welding system with hot-wire feed specifically for this purpose, which uses running gear that moves on a guide ring fixed around the tube.
This new variant has created a lot of interest in the sector, with the worldwide boom in power station construction fueling the never-ending search for increasingly productive manufacturing methods using new types of high-temperature steels.
