What Is Orbital Welding? Joint Types and System Selection

Choose the joint form before choosing the model

A tube-to-tube butt joint, a tube-to-tubesheet seal weld and a U-tube socket joint have different locating and torch-access requirements. For a butt joint, the head works around two aligned ends. At a tubesheet, the torch works relative to the sheet and the tube end. A U-tube configuration must accommodate bend geometry, straight sections and insertion conditions.

The enclosed-head and open-head routes also serve different process needs. Autogenous thin-wall work uses the parent material to form the joint. A prepared pipe groove that needs added metal and multiple passes calls for a filler-capable route. Start with the drawing and the required finished joint, then identify the appropriate equipment family.

The advantage of automation is controlled repetition after a setup has been established. End preparation, internal purge, material condition and inspection remain part of the process. The best machine selection therefore joins mechanical head coverage to an achievable operating and acceptance workflow.

Where FXT20 and C-series enclosed heads fit

FXT20 with a C-series head is an enclosed, autogenous TIG system for tube butt joints. The standard family covers actual OD 6.35–168 mm and wall thickness 0.5–3 mm across different heads; every individual head has a narrower rating. The listed heads are C5, C10, C40, C80, C120 and C170. Select the head and its collets from the actual tube dimensions, then check whether the head can be installed and removed at the intended joint.

Autogenous welding melts the parent material without adding filler wire. That makes a consistent end face and fit-up especially important: there is no added wire to compensate for a poorly prepared gap. The enclosed chamber protects the outside of the hot joint with argon. It does not eliminate the need to establish the required protection inside the tube. Material, purge arrangement and inspection criteria still belong in the procedure review.

The FXT20 power source uses single-phase 220 V input and provides 5–200 A DC output. C5 is air-cooled; C10, C40, C80, C120 and C170 are water-cooled. The host itself is air-cooled, with an internal tank and pump supplying the water-cooled head circuit. These are separate cooling functions. Tube OD 3.175 mm is outside the standard range and requires a paid custom assessment of control precision and current capability. Do not treat a headline family maximum or a custom enquiry as the standard rating of every head.

Where FXT40 Pro and K-series open heads fit

FXT40 Pro with a K-series head addresses open-head industrial TIG welding, including prepared joints that need filler wire and multiple passes. The standard family OD range is 20–325 mm. K76 covers 20–76 mm with a standard wall range of 2–10 mm. K114, K168, K219 and K325 have standard wall ranges of 2–12 mm, with their own diameter coverage. Check the actual head rating before grouping small and large pipe into one package.

The standard three-phase 380 V power-source version provides 10–400 A DC; the optional single-phase 220 V version provides 10–300 A. These are different configurations, so a quotation must identify the intended version rather than combining the current rating of one with the supply requirement of the other. The power source is air-cooled and the K-series head is water-cooled. Site power, cooling connections and the working cable route all need to be included in commissioning planning.

Arc-voltage control and oscillation can help control the process, but arc-voltage control is not automatic seam tracking. Joint alignment, bevel geometry, wire position and the approved pass sequence remain essential. Custom K-series work up to 20 mm wall thickness can be evaluated for a confirmed head, material and procedure; it is not the standard rating of every head. Choose the open-head route because the joint needs its process and access capabilities, rather than assuming that a higher maximum current automatically makes it better for thin clean tubing.

Turn the pipe list into measurable joint families

Start with outside diameter, measured wall thickness, material grade and joint drawing. A nominal pipe label is useful for ordering pipe, but it is not the dimension a weld head clamps. For example, NPS 3 pipe has an outside diameter of 88.9 mm, while a tube sold as 3-inch OD measures 76.2 mm. Those two workpieces may require different heads, collets and preparation equipment. Keep nominal size and actual OD in separate columns instead of converting them informally during purchasing.

Schedule is another label that must be resolved before selection. Schedule 40 does not mean a fixed wall thickness across every pipe diameter. Read the material specification or drawing and enter the actual wall in millimetres. Where metric and imperial tubing coexist, record both units but nominate one controlled dimension for fixtures. Include minimum and maximum manufacturing tolerances when the clamp fit is critical.

Build a joint-family sheet with one row for each combination of OD, wall, material and joint form. Add the required quantity and access condition. A straight tube butt joint, a socket joint and a tube-to-tubesheet joint should not share a selection row simply because their tube diameters are equal. This sheet becomes the basis for head coverage, sample selection, program naming and the configuration review. It also makes gaps in a proposed package visible before an order is placed.

Validate representative joints before releasing production

Use sample joints that represent the intended materials, wall thicknesses and access conditions. A convenient straight tube on a bench may be useful for initial setup, but it does not establish that a crowded assembly or a prepared field joint is ready for production. Include the smallest and largest relevant dimensions and any geometry that changes clamping, gas protection or operator access.

Agree the acceptance plan before the demonstration. Identify who reviews external and internal appearance, dimensions and the required tests. Where a project uses a welding procedure specification and qualification records, align the trial with those requirements. A stored machine program is an instruction to the controller; it is not itself a qualified welding procedure or an approval certificate.

Capture the starting condition as carefully as the finished bead. Record material, end preparation, fixture, electrode setup, gas arrangement, power-source version and program revision. If a test fails, classify the observed problem and change one relevant variable at a time. Repeat with a fresh sample and keep the comparison. This approach is more informative than adjusting several settings until one attractive bead appears.

Before production release, repeat the accepted setup over a representative sequence so that handling, cooling, consumable condition and record collection are exercised together. Include head removal and access to the next joint. The result should be an executable setup sheet and an inspection agreement, not simply a successful photograph. Automation improves repetition when the inputs are controlled; it does not remove the need to establish those inputs.

Practical questions

Is orbital welding always autogenous TIG?

No. The appropriate process and filler requirement depend on the equipment and joint. FXT20 C-series is standard autogenous TIG, while FXT40 Pro K-series supports filler-wire work.

Can a PT head replace a C head at the same diameter?

No. Their joint geometries and locating arrangements differ. Select a tube-to-tubesheet or tube-to-tube configuration from the drawing.

What makes a stored program repeatable?

The program must be used with controlled material, preparation, tooling, gas protection and inspection. Repeating settings alone does not establish joint quality.

Discuss your joint and equipment configuration

Send FYID-Feiyide the actual outside diameters, wall thicknesses, material grades, joint drawing, available working space, site voltage and inspection requirements. Include the expected production mix and any sample-test requirement so the head, tooling and operating workflow can be reviewed together. Contact our team, or compare the system selection guide and model specification tables.