Extreme-Condition Offshore Equipment Fabrication & Duplex Welding

1. The Project Challenge

The marine and deep-sea environment subjects metal structures to severe operational challenges, including immense hydrostatic pressure, cyclic wave loads, and relentless saltwater corrosion. A Tier 1 offshore operator contracted Openex to fabricate a series of critical subsea manifold blocks.

Due to the required Pitting Resistance Equivalent Number (PREN) needed for ocean deployment, the schematics mandated the use of thick-plate Duplex Stainless Steel (2205). Duplex steel is notorious for requiring highly calibrated heat input during welding; if the austenite-to-ferrite ratio becomes imbalanced by poor welding thermal controls, the massive assembly can become brittle and suffer catastrophic structural failure underwater. Furthermore, the completed modules weighed upwards of 150 tons, requiring specialized facility maneuvering.

2. The Openex Solution & Capabilities Engaged

Openex routed this massive subsea component through our heavy fabrication hub, relying heavily on indoor crane capacities and automated weld systems to eliminate variations in manufacturing.

• Automated Heavy SAW Welding: We deployed Submerged Arc Welding (SAW) mounted on automated column booms to process the primary seams. This guaranteed precise heat input and rapid, clean deposition along the thick plates of the sub-assemblies.
• Specialty TIG Root Passes: For critical joints and highly complex pipe/nozzle connections within the manifold, our ASME Section IX master welders performed high-precision manual GTAW (TIG) root passes with internal Argon purging to preserve the Duplex metallurgy.
• Massive Capacity Manipulation: By utilizing massive indoor rotators, the 150-ton steel modules were safely rotated during assembly to allow our welders continuous 1G (flat) welding access, maximizing penetration efficiency and quality.

3. Results and Quality Assurance

Offshore marine components do not get deployed unless they pass uncompromising inspection regimes. The subsea manifolds were subjected to a 100% Ultrasonic Testing (UT) sweep on all primary load-bearing and submerged pressure joints, managed entirely by Openex's in-house Level III NDT team.

The finished components seamlessly passed all strict audits required by international maritime regulatory bodies, including ABS and DNV compliance inspections. They were successfully loaded via heavy-haul transporters from our Xiamen facilities onto port vessels directly for client deployment, delivered on-time and securely within all specified engineering codes.