Two flowlines installed in the Suncor Terra Nova riser replacement programme were found to leak during leak tests performed after site installation. No hydrocarbon loss was suffered nor was there any pollution incident; however the scheduled production start-up for the pipes was delayed. Investigations confirmed that the leaks in both pipes occurred due to a crack in the polymer (PVDF) barrier within the end fitting region of the pipe. It was also concluded that the crack in the barrier in these pipes occurred either during the transportation or installation of the pipes in the field due to thermo-mechanical loading on the pipe during this period. Both failures were found to have initiated from a void in the epoxy which was used to fill small clearances within the end fitting.

This paper describes the finite element stress/stain analyses performed to investigate the effects on the PVDF barrier and epoxy within the end fitting due to the thermal and mechanical loading encountered during pipe installation. A multi-scale modelling approach has been used where a full pipe with detailed end fitting components was modelled in a coarse mesh model whilst the stress-strain behaviour near epoxy void was analysed using a macroscopic sub-model. A brief description of the models and the results are presented.

The analyses involved predicting the barrier deformation response at the failure location under the anticipated thermo-mechanical loading exerted on the pipe. The results have shown that the failure occurred due to the presence of the void in the epoxy at a critical location; cooling of the pipe during its transportation was considered to have created the thermo-mechanical loading to drive the crack from the epoxy into the PVDF. It was concluded that the failure in the pipes would not have occurred if either the void was not present in that critical region in the epoxy, or if it had not been subjected to the thermo-mechanical loading. A design change removing the filling of epoxy in the end fitting process is being implemented to prevent this failure in the future.

This content is only available via PDF.
You do not currently have access to this content.