C120 and FXT20 Planning for DN16-DN100 Closed-Head Tube Welding

Do not assign the complete nominal range to C120

C120 lists actual OD 19–114.3 mm and wall thickness 0.5–3 mm. The lower limit matters as much as the upper limit. If an actual tube OD is below 19 mm, it should not be assigned to C120 simply because the request also includes larger DN labels. Build a row for each actual tube size and map it to an individually suitable head and collet.

Confirm the pipe or tube dimensional standard behind the DN labels, especially where a small nominal label could refer to a different tubing series. Add wall thickness, material grade and joint form to the list. The same FXT20 host can work with different listed C heads, but each family still needs its own setup and validated program.

The public account supports a configuration-planning discussion, not a claim of completed shipment or accepted production. A useful next step is a sample plan covering the relevant smallest and largest tube families and their real access conditions. The following checks make that plan concrete without assuming that one head or one recipe covers everything.

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.

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.

Check the complete installation and removal envelope

Head selection is a geometry problem as well as a diameter problem. Confirm the straight clamping length on both sides of a butt joint, the radial clearance around the tube and the space needed to open or remove the head after welding. Nearby elbows, tees, supports and adjoining tubes can obstruct an otherwise correctly sized head. Check these conditions on a dimensioned assembly drawing or a representative mock-up.

Cable, gas and cooling connections also need a route that stays usable throughout the weld cycle. A fitting that clears the closed head at rest may interfere with opening, unloading or the next setup. Show the operator's working position and the order in which the assembly will be completed. A head that fits the first joint can become trapped when another tube is installed beside it.

For dense manifolds, consider smaller suitable heads, subassembly welding and a planned joining sequence. Each option must still match the specified tube OD, wall and joint form. Do not solve an access problem by assuming an unsupported micro-tube range or by changing the joint design without engineering approval. If a special fixture or custom arrangement is needed, describe the geometry and validate it with the proposed equipment.

Include handling in the trial: load the joint, connect services, weld, cool, remove the head and reach the next location. Time and inspect the full sequence. This establishes whether a configuration can be used repeatedly by an operator in the actual assembly, rather than merely showing that the electrode can rotate once around a tube.

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.

C-series standard head coverage

Practical questions

Does DN16–DN100 automatically fit C120?

No. C120 lists 19–114.3 mm actual OD. Resolve every nominal label and use another suitable head if a tube falls outside its range.

Can the host share programs across different tube families without validation?

Store distinct validated setups as appropriate. Head interchangeability does not make all joint dimensions or materials equivalent.

What should be confirmed before procurement?

Provide the actual OD and wall list, material, joint access, selected fixtures, site power, purge arrangement and inspection plan.

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.