Repair yes, buy the standard part – build-up welding is regulated, the standard part is in stock

Rule of thumb

Build-up welding on an existing part runs under the rules of welding and is the oldest and best-regulated form of additive manufacturing; for flange, elbow, tee and pipe the stock part is faster, cheaper and standardised.

Where does the rule come from?

From maintenance. Building up sealing faces, shafts and stems, cladding walls, compensating corrosion loss – this has been done for decades, to a qualified welding procedure and with testing of the deposit. That it is technically the same as "3D printing with wire" changes nothing in the rules: it is welding. And for everything that has a product standard the opposite applies: do not repair, do not print – buy.

What is technically correct?

Directed energy deposition (DED) builds material onto an existing part – with laser and powder precisely and with low heat input, with arc and wire fast, coarse and on site if needed. The deposit is machined and tested like a weld. Because the base part remains, its identity remains: a repaired flange is still the flange to EN 1092-1 with its certificate, provided the repair is made to the rules and documented. For the standard part, on the other hand, neither printing nor repair pays when the replacement comes from stock: the forged flange, the formed elbow, the standard pipe are denser, faster and orders of magnitude cheaper than any layer-by-layer production – and certified to product standard.

Where does the rule end?

• Whether a repair is permissible is decided, for pressure equipment, by the operator within his risk assessment, if necessary with the inspection body; the rule says "technically and normatively regulated", not "always allowed".
• For large components, long lead times for forgings or special materials the repair may be the choice even where a standard part exists – then for schedule, not for price.
• Repair of castings (valve bodies) follows the manufacturer's rules and the weldability limits of the material.
• "Buy the standard part" presupposes that it exists in size, material and certificate – for special parts the sister rule "three questions before every enquiry" applies.

What does the standard say?

EN ISO 15614 (welding procedure qualification), EN ISO 9606 / EN ISO 14732 (welders and operators), EN 13480-4 (fabrication of piping), AD 2000 HP (fabrication and testing), EN ISO 17635 (NDT of welds); for the products EN 1092-1, EN 10253, EN 10216/10217 (standard parts from stock). Additive manufacturing: ISO/ASTM 52900 (DED as a category), DIN/TS 17026, E EN 13445-14.

DIN/EN versus ASME/ASTM

In the ASME world build-up welding is Section IX (qualification) and, for pressure retaining parts, Code Case 3020 (wire arc additive manufacturing); repairs to pressure equipment are governed by the National Board Inspection Code (NBIC) with the R stamp. The rule holds there too: repair to code, buy the standard part to B16.5 or B16.9.

Worked example

Plant maintenance: the sealing face of a welding-neck flange DN 300 PN 40 is washed out. Two routes: cut the flange out and weld on a new one from stock – downtime with cutting, weld preparation, two new welds and testing; or build up the sealing face by laser or arc and re-machine – on site, to a qualified procedure, with testing of the deposit. At DN 300 the repair usually wins; at DN 50 the new flange from stock. What never wins: printing the flange.

Zickwolff reference

Zickwolff delivers the standard part – flanges, fittings, pipes, valves from stock or to order – and knows from consulting when the repair is the better answer. A dedicated knowledge section on welding is in preparation; repair by build-up welding is the bridge to additive manufacturing there.

Checked today

Traffic light: applies (class A). Build-up welding is fully regulated in the rules of welding; for standard parts there is neither an additive product form nor an economic reason. The permissibility of a repair in the individual case stays with the operator.

Further reading

• Flange standards explained: EN 1092-1, DN, PN, types & sealing faces – flanges from stock
• Test methods explained: destructive, non-destructive – and how much is tested – testing the deposit
• Printed is not standardised – why an additively manufactured part is no standard part – the sister rule
• 3D printing of flanges, fittings, pipes, valves and spare parts in steel: what is technically possible – repair by build-up welding
• Additive manufacturing in piping: what can be printed, what cannot – and why – overview