Stegra — Large Diameter Pipe Prefabrication
Client: WP Welding AB (main contractor) Site: Stegra green steel facility, Boden, Sweden Industry: Steel Production · Green Steel / Hydrogen Period: September – December 2025 Services: Pipe Prefabrication · Industrial Welding
Context
Stegra (formerly H2 Green Steel) is building Europe’s first large-scale green steel production facility in Boden, Northern Sweden. The project is one of the flagship decarbonisation investments on the continent — replacing traditional blast-furnace steelmaking with a hydrogen-based direct reduction process powered by local hydroelectric energy.
Greenfield industrial projects at this scale generate enormous demand for prefabricated process piping. Large-diameter carbon steel pipe sections carry the hydrogen, gases, cooling water, and process fluids that tie the plant together. Prefabrication happens off-site, in fabrication shops, under quality control conditions — then ships to Boden for site installation.
MIDAS was engaged through WP Welding AB to deliver pipe prefabrication for part of Stegra’s process piping network, covering diameters from DN25 (small instrument and process lines) up to DN2000 (large-bore headers for primary process flow).
Scope
Four months of prefabrication output, September to December 2025:
- Fabrication of pipe spools in carbon steel across the full DN25–DN2000 range
- Cutting, bevelling, fit-up, welding, and visual inspection
- Heat number traceability from mill test certificate to completed spool
- Weld numbering and documentation per spool
- Test pack assembly: WPS, weld map, material traceability, NDT coordination
- Load-out for transport to Boden site
The scale is what distinguishes this project. DN2000 carbon steel pipe is heavy — shell alone can weigh several hundred kilograms per meter. Handling, fit-up, and welding at that diameter requires rotating positioners, heavy rigging in the shop, and welders qualified for heavy-section multi-pass welding.
At the same time, the scope included small-bore DN25 lines. The full range from precision instrument tubing to heavy-wall large-bore headers meant crew composition needed welders qualified across the full thickness and diameter spread — something we tracked through our welder qualification matrix throughout the campaign.
Approach
Prefabrication campaigns of this scale depend on three things: material flow, welder allocation, and documentation discipline.
Material flow. Carbon steel pipe and fittings flowed in from main contractor supply. Each item was logged on receipt, heat numbers captured, MTC matched to the list, and staged by spool ID.
Welder allocation. Welders were assigned to spool classes based on their qualification range. Small-bore lines went to welders with strong TIG qualifications. Large-bore heavy-section work went to welders qualified for multi-pass 141 root + 135 fill/cap with SAW capability for the heaviest sections.
Documentation. Every spool left the shop with a complete test pack. WPS referenced, weld map filled in, welders signed off, NDT coordinated, visual inspection recorded. The test pack is the output we deliver, even more than the physical spool — without it, the spool can’t be accepted at site.
Outcome
Across four months of campaign execution, MIDAS delivered large-diameter prefabricated spools into Stegra’s on-site installation programme, on schedule and with complete documentation per spool.
The Stegra campaign is the proof point behind our DN25–DN2000 range claim. Most small welding subcontractors can handle the middle of that range. Very few can genuinely execute both ends of it — instrument-grade precision and heavy-section large-bore — in a single campaign with the same crew discipline.
Stegra is also the proof point for our green-transition readiness. The future of European heavy industry includes more green steel, more hydrogen, more carbon capture. These projects need certified welded piping and they need contractors who can handle it at scale. We’re one of them.
Technical summary
| Scope | Carbon steel pipe prefabrication for process and service piping |
| Diameter range | DN25 – DN2000 |
| Standards | ISO 3834-2, EN 13480-4 (fabrication and installation), EN 1090-2 where adjacent to structural |
| Welding processes | 141 TIG root, 135 MAG fill/cap, 121 SAW on large-diameter positioner, 111 SMAW repair |
| Material | Carbon steel, ISO/TR 15608 group 1.1 / 1.2 |
| Output | Pipe spools with full test pack per spool |
| Duration | September – December 2025 |
| Delivered via | WP Welding AB |
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Large-diameter prefabrication campaigns are scope we actively seek — they play to the capabilities we’ve built. If you have a greenfield or revamp project with significant pipe spool production ahead, send us the isometric package.
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