Offshore oil, gas and marine energy structures · reference card
Fixed platforms, topside piping and subsea pipelines welded under classification-society rules and the transportation codes. The pain points that cost offshore fabricators most, and which Therness signal addresses each.
Offshore fabrication carries every difficulty of structural steel and pipeline welding at once, plus an environment that makes each of them harder. A jacket or topside is structural steel under a design code; the process piping and risers running through it are transportation or plant piping code; and increasingly the record for both has to satisfy the same classification survey.
Access is the recurring problem. A joint welded in a fabrication yard can be inspected from any angle before load-out; the same joint offshore, on a moving vessel or already installed, often cannot. Evidence captured while the weld is made is not a convenience in that setting — it may be the only evidence that will ever exist for that joint.
The design life compounds the stakes. A platform is built to serve for decades against a fatigue and corrosion allowance fixed at construction, so a joint made outside its qualified envelope is a liability that stays invisible until the structure is already in service, far from the yard where the mistake could once have been caught cheaply. The related pipeline application and shipbuilding application cover the two codes offshore work straddles in more depth.
| Code | Why it applies |
|---|---|
| Classification society and offshore structural rules | DNV, ABS and Lloyd's Register each publish rules for offshore units and fixed structures that a fabricator's approval rests on. |
| API RP 2A-WSD | Recommended practice for planning, designing and constructing fixed offshore platforms, covering the structural steel the jacket and topside are built from. |
| AWS D1.1 | Structural welding code commonly invoked for topside and jacket steel alongside the platform-design recommended practice. |
| ISO 3834-2 | Welding quality-system certification widely required of offshore fabricators regardless of which structural rules apply. |
| Pain point | Consequence | Signal that sees it |
|---|---|---|
| Structural and piping welds on the same platform sit under different codes with different evidence expectations | A quality system built around one code leaves gaps when a surveyor asks about the other. | One process record format that carries both structural and piping welds without a translation step. |
| Fabrication happens onshore, offshore and on a moving vessel, each with different access | Inspection coverage that is straightforward in a yard becomes impractical once the structure is on location. | Continuous per-weld thermal and parameter capture that does not depend on physical access after the fact. |
| A platform's design life is measured in decades against a fatigue and corrosion allowance fixed at build | A joint made outside its qualified envelope is a liability that stays invisible until the structure is already in service, far from the yard. | Interpass and heat-input evidence retained for the life of the asset, not just through handover. |
| Class survey windows are short relative to the welding scope on a large structure | A surveyor samples a fraction of the joints, and the rest of the record has to stand on its own. | A complete per-weld record that tells the surveyor where the sample should be taken. |
Therness measures what happens while the arc is running — parameters, thermal signature, per-weld records — so the problems on this page surface on the shift that made them.
Progetto cofinanziato nell'ambito del PR Piemonte FSE+ 2021-2027,
Priorità I, Obiettivo Specifico a), Azione 4 – "Sostegno alla nascita delle start up"
