Part 3: Burst Tests of Pipeline With Extensive Longitudinal Metal Loss

Part 4: Rupture Tests of Pipeline Segments Containing Long Real Corrosion Defects

“…The second article 2 presented the analysis of strain data acquired by using postyield strain gages bonded inside the metal loss areas of different pipe specimens loaded with internal pressure. The third article 3 in the series discussed data acquired for some of the pipe segments that were tested under internal pressure up to rupture and were summarized in Table 1 of Freire et al 2 The measured burst pressures were compared with those predicted by the American Society for Mechanical Engineers (ASME) B31G 4 method, by the Det Norske Veritas (DNV) RP‐F101 (Part B) for single defect 5 recommended practice, and by a recently presented elastic–plastic bilinear (EP‐2) approach 6 . The main characteristics of the specimens were (1) the long or extensive longitudinal defect length and (2) the machining (milled or spark eroded) of the defects.…”

“…Long and short corrosion defects are two types of metal loss damage defect geometries that may occur in oil and gas pipelines 2,3 . The terms “long” and “short” defects are used to mean blunt corrosion flaws, longitudinally oriented, of long or short lengths.…”

“…In the case of smooth or uniform corrosion metal loss, the measured minimum and the calculated average wall thicknesses are enough to give reasonably good predictions of the remaining strength of the defective pipes. The use of level 1 assessment approaches is sufficient to solve those problems, as discussed in Freire et al 3 In the case of irregular‐shaped thickness profiles, level 2 methods are preferable in order to avoid overconservative predictions of the allowable operating pressures. As mentioned previously, 3 quantitative procedures used to evaluate the remaining strength of corroded pipelines are organized in a sequence of three assessment levels.…”

“…The use of level 1 assessment approaches is sufficient to solve those problems, as discussed in Freire et al 3 In the case of irregular‐shaped thickness profiles, level 2 methods are preferable in order to avoid overconservative predictions of the allowable operating pressures. As mentioned previously, 3 quantitative procedures used to evaluate the remaining strength of corroded pipelines are organized in a sequence of three assessment levels. These levels unfold in terms of increasing complexity and associated inherent accuracy (reduction in the inherent conservatism of the method), for obtaining increased information about the properties of the pipe material and the corrosion geometry.…”

“…where S flow is the flow stress, which is defined as the stress required for the pipe steel to plastic collapse. The term D* is related to the pipe diameter used by each method 3 . The term RSF ij is called the remaining strength factor for each combination of adjacent segmented areas of the projected metal loss profile, as given by .…”