St1 Refinery — Three-Phase Turnaround Campaign
Client: WP Welding AB (main contractor) Site: St1 Refinery, Sweden Industry: Oil & Gas · Refinery Period: November 2024 – April 2025 Services: Industrial Welding · Pipeline Installation · Maintenance & Turnarounds · Equipment Installation
Context
St1 operates one of Sweden’s key refineries, supplying domestic and regional fuel markets. Like most operating refineries, it runs on a rolling turnaround programme — scheduled outage windows during which furnaces, heat exchangers, columns, and process piping are inspected, repaired, or replaced.
In late 2024, WP Welding AB — a Swedish welding main contractor — was scoped to deliver welding and mechanical works across three sequential St1 outage campaigns. The challenge wasn’t any single window. It was the cumulative reliability required across three back-to-back campaigns: the same crews, the same documentation discipline, the same safety record, delivered three times in a row with no slip between windows.
MIDAS was brought in as WP Welding AB’s welding subcontractor for all three phases.
Phase 1 — Furnace Turnaround, November–December 2024
Scope: Refinery turnaround works focused on furnace repair. Welding and installation of process piping in confined and hard-to-access areas under active PTW regime.
Furnace work is some of the hardest welding in a refinery environment. Access is tight. Preheat is typically required. The position is often overhead or 6G. And the consequence of a weld defect on a furnace tube is a forced outage extension nobody can afford.
Our crew delivered:
- Welding of furnace-adjacent piping per client WPS
- Repair welding of identified weld defects and corroded sections
- Integration into daily PTW briefings and hot work permit procedures
- Full weld documentation and traceability to welder ID
Phase 1 handed over on schedule with all welds accepted on first-pass inspection for the critical scope.
Phase 2 — Furnace Turnaround Continuation, January 2025
Scope: Repair of Furnace No. 2 during a subsequent shutdown, mid-January to end of January 2025. Welding and piping installation works.
Phase 2 came two weeks after Phase 1 handover. For MIDAS, this meant demobilizing and re-mobilizing the same crew back to the same site within a window too short for any new welder qualification testing. Our welding coordination had the qualification matrix ready, the scope was pre-briefed, and the crew walked back onto site pre-inducted.
Delivered:
- Furnace tube and header welding
- Process piping installation and tie-ins
- Continued integration into main contractor’s QA/QC documentation stream
The back-to-back nature of Phase 1 → Phase 2 is what the St1 case study demonstrates more than any individual scope element: our crews can be re-deployed on consecutive windows without ramp-up time loss.
Phase 3 — Equipment Installation, March–April 2025
Scope: Turnaround works at the refinery focused on equipment installation. Installation of new process equipment and associated piping systems.
Phase 3 shifted focus from repair to new-build-in-place. Process equipment — new units installed on existing foundations, tied in to existing process piping — requires both mechanical installation discipline and welded tie-in integrity.
Delivered:
- New equipment placement coordination
- Tie-in welding to existing process piping
- New piping fabrication for tie-in spools
- Pressure testing and handover to commissioning
Outcome
Across the three-phase campaign, MIDAS delivered:
- Welding and piping scope across five months of intermittent outage windows
- Back-to-back crew deployment across all three campaigns
- Full documentation handover per phase
- Integration with WP Welding AB’s main contractor QA/QC and HSE systems
The reliability of delivering three consecutive St1 outage windows has made the St1 campaign MIDAS’s most-referenced project to date — and the proof point behind our “mobilization speed” claim.
Technical summary
| Scope | Furnace repair, process piping, equipment installation |
| Standards | ISO 3834-2, EN 13480, client plant-specific specs |
| Welding processes | 141 TIG, 135/136 MAG, 111 SMAW |
| Materials | Carbon steel pressure grades |
| Access conditions | Confined, overhead, positional, hot work PTW |
| Duration | 3 campaigns, November 2024 – April 2025 |
| Delivered via | WP Welding AB |
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