It runs a stored program rather than a fixed setting. The supply sequences purge, upslope, a series of sectors with individually set current and travel, then downslope and overlap, while simultaneously driving head rotation and wire feed as coordinated axes. A standard TIG machine controls current only, and has no means of varying it against angular position around the joint.

Typically actual welding current, arc voltage, rotation speed, wire feed rate, gas flow and elapsed time, sampled through the weld and stored against a weld identity number, program number, operator and timestamp. The file exports for the QA package. Because it captures actual rather than commanded values, it is evidence the joint ran at qualified parameters.

Wall thickness and diameter set the current demand, and duty cycle sets whether the machine can sustain it across a shift. Thin-wall instrumentation tube needs relatively little output, while heavy-wall pipe with multi-pass filler can call for several times as much. Size on the heaviest joint in the scope, not the average, and confirm the rating at the ambient temperature of the site.

Within a manufacturer's range, generally yes, provided the control interface supports the head type. Enclosed heads need rotation control and gas sequencing; open heads add wire feed, oscillation and often arc voltage control for automatic torch height. Heads are not interchangeable between manufacturers, so the head range effectively decides the supply, not the reverse.

It holds the arc length constant by measuring arc voltage and adjusting torch height in real time. On multi-pass open-head welding the surface the torch travels over rises with each pass and is never perfectly round, so without it the arc length drifts and penetration with it. Enclosed autogenous welding on true tube rarely needs it.

Many are built for it, with case-mounted handles, sealed enclosures and tolerance of generator supply. The practical constraints on site are weight where the unit must be carried into a plant room, the quality of the incoming supply, and protection of the head connectors from dust and damage. Shop-based systems trade portability for higher output and duty cycle.

A program is developed on test coupons of the actual material, wall and heat, then verified by sectioning or by the acceptance criteria in the governing standard. Once proven it is locked and issued under a program number tied to the weld procedure. Uncontrolled editing at the machine is the usual route to unqualified welds, so access is normally password protected.