Subsea Structure Steel Supply | STS Case Study

Sector: Upstream Oil & Gas — Subsea Structures Client: Two of Perth's leading steel fabricators Scope: Offshore structural steel for the fabrication of subsea mudmat, manifold, and protection structures for projects including the Jansz-Io project and the Scarborough project. Location: Perth, Western Australia Status: Completed

The Jansz-Io project and the Scarborough project are two of the most significant offshore gas developments in Australian history. The Jansz-Io project involved the fabrication of what are understood to be the largest subsea mudmats ever built, alongside complex subsea manifold structures, all requiring offshore structural steel to exacting specifications. Both projects faced a common challenge: the need for offshore structural steel grades, specifically EN10225 offshore structural plate, beams, and tubulars, which are not available in the Australian market.

Perth's fabrication community had the capability to win work on both the Jansz-Io project and the Scarborough project. What they lacked was access to the right offshore structural steel material. 

EN10225 offshore structural steel is not produced or stocked locally in Australia. Without a reliable, cost-competitive supply route for compliant offshore grade material, local fabricators faced the real prospect of losing these packages to overseas yards. 

A further complication: the EPC's specification referenced an older version of EN10225, creating a technical compliance challenge that required careful management to align currently available material with the project's purchase order requirements.

STS worked directly with two of Perth's largest fabricators to build a supply solution that made local participation viable for both the Jansz-Io project and the Scarborough project. 

We sourced EN10225 offshore structural steel, including structural plate, beams, and tubulars from qualified mills in Europe and South East Asia, selecting supply routes based on both delivered cost and lead time to keep pace with each fabricator's production programme. 

On the technical side, our team supported the EPC and fabricators through the specification deviation process, preparing and submitting technical queries and deviation requests to align current EN10225 material with the legacy specification referenced in the purchase orders. 

We then managed the complete logistics chain and international freight, customs clearance, local transport, and final delivery to each fabricator's door. Both yards received their material on time, with full documentation packages, including mill test certificates, inspection reports, and certificates of conformance ready on arrival.

Both fabricators successfully delivered their scopes of mudmats, manifolds, and protection structures on the Jansz-Io project and the Scarborough project, with Perth-based fabrication retained on two of Australia's most prestigious offshore projects. 

The mudmats for the Jansz-Io project are understood to be the largest ever fabricated. By providing access to offshore structural steel that is unavailable in Australia and managing the full supply chain to the fabricators' doors, STS directly enabled local businesses to compete for and win major subsea scopes, thereby keeping the work, jobs, and economic value in Western Australia.

EN10225 offshore structural steel — including plate, beams, and tubulars — is essential for projects like the Jansz-Io project and the Scarborough project. We focus on multi-source supply optimization across Europe and SE Asia, ensuring technical deviation support for legacy EN10225 specification management. Our end-to-end logistics cover everything from international freight to delivery at the fabricator's door. We also provide third-party inspection and full material traceability. Our parallel supply capabilities allow us to support multiple fabricators working on concurrent projects while promoting Australian local content on major offshore projects.