Pipe Prefabrication

What this service is

Off-site fabrication of pipe spools and welded piping assemblies to client drawings, with full weld traceability and documentation package. Prefabrication moves welding work off the live-plant critical path, improves quality control through environmental stability, and lets site installation windows stay focused on fit-up rather than production welding.

We prefabricate from carbon steel through duplex stainless, across the full DN25–DN2000 diameter range. Spool output is delivered ready for site install — cut, bevelled, welded, NDT-accepted, marked, and packed.

Scope

What a prefab package includes:

• Drawing review, material take-off (MTO), cut list generation
• Material receipt, heat number traceability, mill test certificate (MTC) matching
• Cutting, machining, and bevelling
• Fit-up with tacking and dimensional verification
• Welding per WPS (root → fill → cap)
• Visual and dimensional inspection, in-house
• NDT coordination where specified (RT / UT / PAUT via partners)
• Spool marking per client spec
• Test pack assembly: isometrics, WPS, weld map, NDT reports, MTCs
• Protective coating application (optional, partnered)
• Load-out and transport coordination

Typical prefab shop deliverable: a numbered spool with a complete traceability pack, ready to bolt into position on site.

Codes and standards

• EN 13480-4 — Metallic industrial piping — Fabrication and installation
• ISO 3834-2 — Comprehensive welding quality framework
• EN ISO 15614-1 — Welding procedure qualification
• EN ISO 9606-1 — Welder qualification
• PED 2014/68/EU — Pressure equipment compliance
• ASME B31.3 — Where process piping falls under ASME scope
• EN ISO 5817 — Weld quality levels per spool class

Test pack format follows client template where provided, or our standard template where not. Electronic and hard-copy delivery both supported.

Materials and thickness

Thickness range: 2 mm through 60 mm in standard execution.

Welding processes for prefab

Prefabrication allows process selection optimized for productivity, not site constraints:

• 141 TIG — root passes on stainless, duplex, and small-diameter carbon steel
• 135 MAG solid wire — fill and cap on carbon-steel pressure spools
• 121 Submerged arc (SAW) — heavy-wall large-diameter carbon steel on positioner
• 111 SMAW — backup and repair

The ability to run SAW on a rotating positioner is one of the main productivity differences between prefab and site welding. We qualify and run it where spool geometry allows.

Diameter range

• DN25 through DN2000
• Schedule: SCH 10 through XXS
• Bend and fit geometry: prefab accepts isometrics with field elbows, tees, reducers, caps, and flanged ends per drawing

The DN2000 upper limit is what we delivered on Stegra — large-bore carbon steel pipe sections for green steel production. Larger is a conversation worth having.

Quality control in the prefab shop

• Dimensional check — every spool checked against isometric before welding and after welding for dimensional drift
• Visual inspection — 100% VT per EN ISO 17637
• NDT — coordinated with approved partner, typically 10–20% RT on critical butts, 100% RT on high-class spools
• Traceability — every weld mapped to welder ID, WPS, material heat number, filler lot, and inspection record
• Documentation — handover test pack per spool

Prefab allows a higher first-pass NDT acceptance rate than site work because the environment is controlled — no wind, no rain, no positional constraints. Our target is ≤1% rejection on first-pass RT for prefab butts.

Where we’ve delivered this service

• Stegra (H2 Green Steel), Sweden — DN25–DN2000 carbon steel pipe section prefabrication for green steel facility
• RECION OY, Finland — prefabrication of black-steel piping systems, spools and welded assemblies for industrial installation

→ See all 9 projects

Frequently asked

Do you have your own prefab shop or do you rent capacity? Prefabrication is executed per-project, with shop arrangements confirmed at RFQ stage — either at MIDAS-controlled facilities or at a main contractor’s shop with our welding crews running the line. Both models have delivered the same quality output.

What’s your typical spool output per welder per shift? Varies by diameter, wall thickness, and material. For DN80 Sch 40 carbon steel in TIG-root/MAG-fill, a welder typically produces 4–8 butts per shift. Larger DN400+ SAW on positioner can run 1–2 butts per shift. Detailed production estimates are part of RFQ response.

How do you handle material supply and traceability? Client supply or MIDAS procurement, per contract. In both cases, every pipe, fitting, flange, and filler is tracked by heat number to MTC. The test pack delivered with each spool lists every traceable component.

Can you prefabricate to ASME B31.3? Yes. WPS and welder qualifications are maintained to both EN ISO 15614-1 and where required ASME Section IX. Client specification drives which framework applies to each spool class.

How is prefab different from the “Pipeline Installation” service? Prefab is off-site spool production. Pipeline Installation is the on-site work from receiving prefabricated spools through to pressure test. Many projects need both — we can deliver them separately or as one package.

Can you coordinate coating and insulation after welding? Coating yes, via partnered shops. Insulation is typically a site-applied follow-on and we don’t offer it directly. We do ensure spool preparation is insulation-ready on handover.

Request a quote

Send us isometrics, material list, and target delivery dates. We’ll respond within one business day with cut list, WPS mapping, and production schedule.

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