19 GTAW Orbital Welding

Orbital welding is most commonly used with GTAW for welding tube to tube and tube to tube fittings, pipe to pipe and pipe to pipe fittings, and tube to tube sheet. (Tube sheet is metal plate with regularly spaced holes designed to support and isolate the dense array of tubes in heat exchangers and boilers.) Orbital GTAW can be used on a variety of materials, including carbon steels, alloys steels, stainless steels, titanium, nickel, copper, and aluminium alloys. Orbital GTAW is typically specified where high internal weld quality is required, such as in semiconductor clean rooms, in the pharmaceutical and food processing industries, in the petrochemical industry, with power generation, and with aerospace applications.

Specialized, closed-chamber weld heads are available for orbital GTAW applications involving tubes with diameters ranging from 1.6mm to 170 mm (0.0625” to 6.7”) and wall thicknesses of up to 3.5mm (0.14”). Closed-chamber weld heads hold a joint in alignment and ensure complete shielding gas coverage of the weld area. Alternatively, open welding heads combined with special running gear around the circumference of the pipe can make it possible to use orbital GTAW on large-diameter pipe, such as those used as water intake pipes for hydroelectric power plants.