32" Mechanically Lined Pipe Qualification

The Challenge

A major Caspian field development required corrosion-resistant lined pipe at a diameter well beyond anything previously qualified for reel-lay installation. Mechanically lined pipe relies on a residual interference fit between the carbon steel backing and the CRA liner — an interface that is progressively challenged every time the pipe is spooled, straightened and re-spooled.

At 32 inches, liner wrinkling and collapse during reeling were credible failure modes with no precedent to fall back on. No existing qualification covered the diameter, and the project could not proceed to installation without one.

Our Approach

The largest mechanically lined pipe ever qualified for reel-lay — analysis and full-scale test correlated, not one substituted for the other.

VORYX team members led the qualification programme end to end, combining nonlinear finite element analysis with full-scale physical testing rather than relying on either alone. The FE model captured liner–backing contact, large plastic strain, residual interference and the complete reeling load history — spooling, straightening, laydown and hydrotest in sequence.

Strain-based design was applied where reeling imposes displacement-controlled deformation, with engineering critical assessment to BS 7910 and DNV-RP-F108 used to derive weld flaw acceptance criteria that fabrication and NDT could actually work to.

A full-scale reeling simulation programme validated the analysis. Test results were correlated back to the FE model, closing the loop between prediction and measured behaviour and giving the third-party verifier a basis to accept the qualification.

Standards Applied

• DNV-ST-F101
• DNV-RP-F108
• BS 7910
• API 5LD
• DNV-RP-F112

Operator and project names are anonymised for confidentiality and disclosed on request. Experience described is that of VORYX team members.