Development of a Mechanical Damage Classification System for Use in the Post Construction Code for Nonmetallic Repair of Piping and Pressure Vessels

Abstract

ASME PCC-2, Repair of Pressure Equipment and Piping, Article 4.1, addresses the repair of high-pressure systems with nonmetallic composite systems and generally permits the repair of dents and gouges in paragraph 1.2(b) with certain substrate preparation requirements. Research done at The University of Tulsa along with meta-analysis of the work preformed over the last three decades at PRCI, GRI and Battelle has shown that classification of mechanical damage must be further refined and delineated to adequately address all applicable facets of non-metallic repair. This paper covers the author’s work with the Nonmetallic Repair Subgroup (SG NMR) to classify types of mechanical damage and the associated permissible repair methods. These damage classifications are set to be included in future editions of the PCC-2. The types of mechanical damage that were considered for this research were dents, cracks, gouges and certain repairable combinations of the three. Specific definitions are laid forth for the damage types and their subclasses along with geometric nomenclature in an attempt to standardize classification across the differences in the international standards. Other forms of mechanical damage and associated amplifying factors exist and are issues that pipeline and refinery assurance managers are concerned with. Additional examples of mechanical damage that are often considered for non-metallic repair are wrinkles and wrinkle bends, creases, buckling points and seismic folds. A common amplifying factor for mechanical damage is that increased corrosion rates often appear at the site of damage due to breeching of protective coatings or creation of extreme geometries that facilitate crevice corrosion, or the development of residual stresses.