Planned maintenance turnarounds are among the most consequential operational events in a refinery’s calendar. The Soyo refinery’s 2025 major turnaround, executed over a 42-day window from September through November, provided an opportunity to assess the facility’s maintenance management maturity, local content capability, and readiness for the next operational cycle.
Scope and Execution
The 2025 turnaround encompassed work across the crude distillation unit, vacuum distillation unit, naphtha hydrotreater, diesel hydrotreater, and associated utility systems. The scope included inspection and repair of over 400 static equipment items, replacement of 12 heat exchanger bundles in the crude preheat train, installation of new column internals in the atmospheric tower, and comprehensive inspection of pressure vessels and piping circuits.
Peak workforce during the turnaround reached approximately 2,800 personnel, including 1,600 contractor personnel from international specialized maintenance firms and 1,200 Angolan nationals. The local content ratio of 43% represented an improvement over the 2021 turnaround (35%) but remained below the government’s aspirational target of 50% for downstream maintenance activities.
Cost Performance
The total turnaround cost came in at approximately $145 million, representing a 12% overrun against the original budget of $129 million. The primary sources of cost variance were scope growth driven by inspection findings (particularly corrosion-related repairs in the vacuum unit overhead system), foreign exchange movements affecting imported material costs, and extended duration of certain critical path activities.
On a per-barrel-of-daily-capacity basis, the turnaround cost equated to approximately $725/bpd, which compares to a global benchmark range of $500-$800/bpd for turnarounds of similar scope. The Angolan operating environment imposes a cost premium of approximately 15-25% relative to turnarounds in mature refining centers, primarily driven by logistics costs and the need for imported specialized labor.
Key Findings and Remediation
Inspection findings during the turnaround identified several conditions requiring attention beyond the planned scope. The most significant was accelerated corrosion in the vacuum unit overhead system, attributed to changes in crude quality that increased naphthenic acid content above the design basis. Remediation included replacement of affected piping sections with upgraded metallurgy (317L stainless steel) and installation of online corrosion monitoring probes.
Other notable findings included fouling in the crude desalter that was reducing salt removal efficiency, wall thinning in several heat exchanger shells approaching minimum retirement thickness, and degradation of catalyst in the naphtha hydrotreater that warranted early replacement ahead of the planned catalyst cycle.
Implications for Next Cycle
The 2025 turnaround findings have informed the planning basis for the next major maintenance window, scheduled for 2029. Key planning considerations include proactive metallurgy upgrades in corrosion-susceptible circuits, expansion of online monitoring to enable condition-based rather than time-based maintenance intervals, and increased investment in local workforce capability development to improve the local content ratio and reduce dependence on imported specialist labor.
The intermediate maintenance window planned for 2027 will focus on targeted interventions in systems flagged during the 2025 turnaround, with a reduced scope and shorter duration targeting 12-15 days.