TWI Industrial Member Report Summary 394/1989
M D F Harvey
A wide range of mechanised orbital TIG welding equipment is now available to the process pipe fabricator, ranging from basic function systems for stringer bead welding to full function systems featuring automatic arc voltage control, mechanical welding head oscillation and synchronised pulsed welding current with pulsed wire feed and pulsed travel. The degree of sophistication is reflected in the cost of the equipment.
This report describes the modification of a simple basic function orbital TIG welding system, capable of stringer bead passes only, to facilitate magnetically controlled arc oscillation as an alternative to mechanical welding head oscillation.
Welding procedures were developed in the 5G (horizontal) position for 60mm OD X 5.7mm wall (2in NB Schedule 80), Type 304 stainless steel pipe using magnetically controlled arc oscillation. This was chosen as being typical of a range of pipe sizes which, when welded using a mechanised stringer bead procedure, did not meet the BS 4677: 1984 requirements on bore constriction.
Comparison welds were made manually and using mechanised equipment with both stringer bead and weaving procedures.