Open Weld Heads for Orbital Exterior Diameter Welding

AMI Model 79 series open weld heads

Automated orbital welding offers many advantages over manually welding piping systems. Consistency, higher quality, lower overall cost, and faster project completion are just a few reasons to employ an orbital welding approach. Additionally, orbital welding enables the operator to work at a safe distance from the weld puddle and any potentially toxic fumes. To meet your project needs, the industry leader in orbital welding equipment, Arc Machines Inc. (AMI), offers you a choice of weld head types for external or outer diameter welding: open and closed configurations. 

Why Open Weld Heads?

AMI’s open and closed orbital weld heads both deliver high-quality weld results. However, there are times when one is preferable. Although closed weld heads are compact and reduce exposure to shielding gases, open weld heads can be used in much tighter environments. For example, open weld heads offer advantages when welding onsite and angular movement is limited or pipes are tightly arranged.  

When using AMI’s open weld heads, you can expect superior performance and features as listed below for the Model 79 series.

  • Arc Voltage Control (AVC) for precise arc gap control.
  • Programmable oscillation and motorized cross-seam positioning.
  • Precision wire feeder with wire guide positioner.
  • Standard is without cameras, option to have dual cameras & motorized wire positioning.
  • Integral clamping system with the ability to adjust for different pipe and tubing diameters in seconds.
  • Clamping mechanism allows automatic centering of the weld head on pipe.
  • Water cooled torch for 100% Duty Cycle operation.

Choosing the Best Open Weld Head Orbital Equipment

AMI offers several options for open weld heads, as shown below. 

AMI’s Open Weld Heads

Open Weld Head Compatible Power Source(s) Max 

Wall Thickness


Pipe OD


Pipe OD

79 -2375 227, 415 0.44 in (11 mm) 0.75 in (19 mm) 2.375 in (61 mm)
79 -3500 227, 415 0.44 in (11 mm) 1.0 in (25 mm) 3.5 in (90 mm)
79 -4500 227, 415 0.675 in (17 mm) 1.9 in (48 mm) 4.5 in (114 mm)
79 -6625 227, 415 0.75 in (19 mm) 2.0 in (50 mm) 6.625 in (170 mm)

To maximize performance for exterior diameter welding, you need the right electrode. AMI offers tungsten electrodes that match or exceed any in the industry. 

AMI Tungsten Electrodes

AMI provides ground and polished electrodes that will meet your open weld head orbital project needs for industries including food processing, pharmaceuticals, energy generation, and other high-spec projects

Electrodes Description Common Applications
Pure 99.5% or higher purity. Good ignitability. AC welding of magnesium and aluminum.
Thoriated Up to 4% thorium dioxide. Very versatile. Used when stable electron exit is required, such as in narrow gap welding.
Lanthanated 2% or less lanthanum (III) oxide. Most versatile electrodes. Aluminum welding with AC. 
Ceriated Increasingly used to replace thoriated tungsten electrodes. Best for low current use.
Zirconiated Only 0.8% zirconium oxide Used to create high-purity TIG welds. 

As shown above, AMI tungsten electrodes have varied use cases; however, all can be used for consistent, high-quality TIG welding. Additional equipment, though, is necessary to complete and optimize your open weld head orbital system.

Other Equipment

In addition to industry-leading open weld heads and electrodes, AMI also delivers advanced equipment as listed below.

If your application calls for open weld head orbital diameter welding, look to the experts at AMI for the best equipment to suit your project needs.


Arc Machines, Inc., since its founding by former NASA engineers in 1976, has been an industry leader in delivering high-quality and high-tech welding equipment. This includes open weld heads for orbital exterior diameter welding and high-grade reliable tungsten electrodes. For inquiries regarding products, contact For service inquiries, contact Arc Machines welcomes the opportunity to discuss your specific needs. Contact us to arrange a meeting.