ISO 24817 and ASME PCC-2 Article 401 provide guidance on the use of composite materials for repair of pressurised piping. This paper will provide the clarity required to ensure the repairs specified using these standards will fully restore the capacity of impaired pipelines and will focus on:
- Selection of the relevant design requirement/intent and design factor, and how to account for the original Location Class used in the design of the pipeline.
- Appropriate consideration of the contribution of the original line and the proportion of pressure it will carry in a repaired line.
- Interpretation, limitations and use of the performance testing requirements (specified in ISO 24817 Annex E and ASME PCC-2 401-V) in determining the thickness of repair required, with quantification of the effects of assuming that pipelines behave perfectly plastically in the derviation of long-term design stress / strain for the repair.
- How to treat Poisson's ratio effects on repair thickness. ISO 24817 either discounts the effect or assumes the contribution increases repair thickness whereas ASME PCC-2 401 either discounts the effect or assumes it acts to reduce the repair thickness required. The differences in approach will be reviewed and clear recommendations for reliable design consideration provided.
- The effect of line pressure at time of installation will be considered and the impact on repair thickness derived quantified. Recommendations for future updates to the requirements in the stanardard will be made.
- Calculation methods for considering defects other than wall thinning due to external corrosion will be presented (e.g. crack-like features).
It is intended that this paper will provide a technical basis and starting point for the future revisions of both standards.