Mobile close proximity orbital welding system having a shielded weld zone

An orbital welding system for joining a riser to a pulled collar on a manifold runner with a circumferential weld bead, comprising:

• a) a multi-axis welding platform including a base plate defining a horizontal plane, a lift plate adjustable along a vertical axis relative to the base plate, a lower slide plate adjustable within a first horizontal plane relative to the lift plate along a first horizontal axis, an upper slide plate adjustable within a second horizontal plane relative to the lower slide plate along a second horizontal axis that is perpendicular to the first horizontal axis, and a tilt stage assembly including a lower tilt plate defining a third horizontal plane and an upper tilt plate that is adjustable within a tilt plane relative to the lower tilt plate;
• b) a weld head assembly supported on the upper tilt plate of the tilt stage assembly of the multi-axis welding platform and including a shaft housing, an elongated radially outer electrode drive shaft mounted for axial rotation within the shaft housing, a drive motor operatively connected to the electrode drive shaft for axially rotating the electrode drive shaft relative to the shaft housing, and an elongated non-rotating radially inner insulated support shaft extending coaxially through an axial bore of the outer drive shaft;
• and
• c) a torch assembly including a dual-axis slide mechanism coupled to an upper end portion of the electrode drive shaft so that the torch assembly rotates coaxially with the electrode drive shaft, an elongated vertical torch shaft extending from the dual-axis side mechanism, and an electrode holder connected to an upper end portion of the vertical torch shaft for retaining a tungsten electrode.