Structural integrity evaluation of X52 gas pipes subjected to external corrosion defects using the SINTAP procedure H. Adib-Ramezani a, * , J. Jeong a , G. Pluvinage b a Ecole Polytechnique de l’Universite ´ d’Orle ´ans, CNRS-CRMD, 8 rue Le ´onard de Vinci, 45072 Orle ´ans Cedex 2, France b Laboratoire de Fiabilite ´ Me ´canique (LFM), Universite ´ de Metz-ENIM, 57045 Metz, France Received 27 July 2005; received in revised form 26 December 2005; accepted 1 February 2006 Abstract In the present study, the SINTAP procedure has been proposed as a general structural integrity tool for semi-spherical, semi-elliptical and long blunt notch defects. The notch stress intensity factor concept and SINTAP structural integrity procedure are employed to assess gas pipelines integrity. The external longitudinal defects have been investigated via elastic–plastic finite element method results. The notch stress intensity concept is implemented into SINTAP procedure. The safety factor is calculated via SINTAP procedure levels 0B and 1B. The extracted evaluations are compared with the limit load analysis based on ASME B31G, modified ASME B31G, DNV RP-F101 and recent proposed formulation [Choi JB, Goo BK, Kim JC, Kim YJ, Kim WS. Development of limit load solutions for corroded gas pipelines. Int J Pressure Vessel Piping 2003;80(2):121–128]. The comparison among extracted safety factors exhibits that SINTAP predictions are located between lower and upper safety factor bounds. The SINTAP procedure including notch-based assessment diagram or so-called ‘NFAD’ involves wide range of defect geometries with low, moderate and high stress concentrations and relative stress gradients. Finally, some inspired and advanced viewpoints have been investigated. q 2006 Elsevier Ltd. All rights reserved. Keywords: Gas pipeline; External corrosion defects; SINTAP; Notch stress intensity 1. Introduction Pipelines have been employed as one of the most practical and low cost methods for oil and gas transmission since 1950. Pipeline installation for oil and gas transmission has drastically increased in the last three decades. The economical and environmental considerations involve struc- tural integrity and safety. Therefore, reliable structural integrity and safety of oil and gas pipelines under various service pressure events including defects should be warily evaluated. The external defects, e.g. corrosion defects, gouges, foreign object scratches and pipeline erection activities are major failure reasons of gas pipelines. In the present work, finite element stress analysis for API X52 is performed including longitudinal external defects under high internal pressure. The failure assessment and structural integrity of the gas pipeline have been compared with SINTAP failure assessment levels (levels 0B and 1B) [2] and limit load analysis (ASME B31G, modified ASME B31G, DNV RP-F101 and Choi et al. [1]). The elastic–plastic finite element analysis is utilized and the SINTAP procedure is applied to the notch problem for calculating the structural integrity of the considered pipelines. 2. Assessment of corrosion defects In Fig. 1, a list of methods available for corrosion defect assessment is presented. The methods are grouped vertically by their type, codified methods or others, and horizontally by their applicability, pressure or combined loading, etc. The structural integrity of corrosion defects is substantially studied and the outcomes for gas pipelines are classified in ASME B31G [3] and DNV RP-F101. In Fig. 1, the coded methods, i.e. ASME B31G, modified ASME B31G [4,5] and DNV RP-F101 are taken into account. Moreover, the SINTAP procedure is also considered to be investigated for the structural integrity assessment of corroded pipelines. In the present study, corroded pipes under pressure excluding combined loading and external force are addressed. International Journal of Pressure Vessels and Piping 83 (2006) 420–432 www.elsevier.com/locate/ijpvp 0308-0161/$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijpvp.2006.02.023 * Corresponding author. Tel.: C33 2 384 94992; fax: C33 2 384 17329. E-mail address: hradib_2000@yahoo.com (H. Adib-Ramezani).