Orbital welding is a very specialized area of welding. It is a type of arc welding where the arc is rotated by machine around a static workpiece – such as a pipe – a full 360 degrees. It is an automated process and can be very useful. Pipes that are as large as several centimeters around or even as small as just a few millimeters can all be welded this way. It is a process that was developed over fifty years ago.
There are several main components that make up an orbital welding system. These components are the controller and power source, welding head, and in some cases a wire feed mechanism. There are many factors that have an influence on the results of the welding. Some of the most significant parameters are the magnitude, arc length, and the welding current's pulse frequency, the parent material and filler material, welding speed, weld preparation, inert shielding gas, thermal conductivity, and weld preparation. The way to ensure a high quality weld is to have detailed knowledge about how to adjust all of these individual parameters precisely enough for every welding task.
Manual welding is very tricky because in order to meet the highest standards of safety and quality a perfect balance has to be found between surface tension and gravitational force in each position that the torch is in. But when the system has mechanized components, certain parts of the process are handled by components that are mechanical while a welder controls and monitors the entire process. While it would be perfect for all the welding parameters to already be programmed in before welding ever begins, the reality is that a welder has to often make corrections throughout the process. If the entire process is automated, a computer controls the welding process and there is no need for the operator to intervene at all.
Orbital welding is carried out using Tungsten Inert Gas (TIG) techniques. It uses non-consumable electrodes and when necessary, a cold-wire feed. There are many kinds of metal that can be welded: copper, titanium, aluminum and associated alloys, nickel alloys, high strength, corrosion resistant and high temperature steels, low alloyed and unalloyed carbon steels, and nickel alloys. Because the process is carried out in an atmosphere that is inert, results that are produced are extremely clean, with no unwanted spatter and having low particle counts.
The tiniest diameters of just 1.6 millimeters can be welded using orbital welding. Pipes that are up to 170 millimeters with 3.5 millimeter thick walls can also be welded using weld heads that are closed chamber. Closed chamber weld heads let the pipe be held securely and the torch positioned precisely. Even the most sensitive materials will not have tinting from heat thanks to the inert atmosphere. If tubes are in diameters that are between 8 and 275 millimeters, open welding heads that are more easily manageable can be used. Flexible hoses supply power, cooling water, inert gas, and filler wire to the welding head when it is required. Whether or not filler wire is needed depends entirely on the task. For example, thin-walled tubes need no extra wire but thick-walled materials will. Tube ends must be carefully prepared and the work pieces must have no scale or impurities.
Orbital welding is used in the semiconductor industry in the clean rooms. It's use has also expanded to the building of equipment and pipework for industries such as pharmaceuticals, food processing, chemical engineering, automotive engineering, shipbuilding, biotech, and aerospace. It's even used in thermal power plants. There are many openings for this type of welding to be used and there is a need for welders who can program the systems.
