Integrating Automated Ball Indentation With ASME B31G Code to Assess Integrity of Corroded Pipelines Available to Purchase

In order to provide deterministic structural integrity assessment for safe and efficient operation of corroded pipelines, the following information is required: (a) the actual key mechanical properties (yield and ultimate strength, and fracture toughness) of the pipeline materials, (b) the present thickness and diameter of the pipeline, and (c) the profile of the maximum depth of corrosion pits over the pipeline axial length, and the size of sharp cracks. Both items (b) & (c) can be determined by conventional techniques. A patented in-situ Stress-Strain Microprobe (SSM) system was used to provide item (a), the required key mechanical properties (tensile and fracture toughness), in a nondestructive and localized fashion without any interruption of the pipeline transmission using its novel Automated Ball Indentation (ABI) test technique. The SSM system was used on a short segment of a 356-mm (14-inch) diameter Kerosene pipeline. Although there was no documentation of the pipeline steel grade, the minimum ABI-measured yield strength at four locations was 277 MPa (40.2 ksi) and the minimum ultimate tensile strength was 378 MPa (54.8 ksi) indicating that the steel met the requirements of Grade “A”. Both the Rstreng software and the ASME B31G code were used to calculate the maximum safe operating pressure for the corroded pipeline. The calculations showed that a profile with a few corrosion pits [3–6 mm (0.075–0.236 inch) maximum depth spaced over 483 mm (19 inches) length] reduced the maximum safe pressure significantly from 4.24 MPa (615 psi) to 0.74 MPa (107 psi). The operator of the pipeline limited the maximum operating pressure to 0.69 MPa (100 psi). Furthermore, it was recommended that the ABI measurements be performed on at least 10% of the 7-km Kerosene pipeline and on all patches and welds in order to provide the minimum yield strength values required for determining the remaining strength of the pipeline. This work proves that the integration of the ABI measurements with the corrosion pitting profile allows calculation of the maximum safe operating pressure in order to make the appropriate decision of replacement or repair of certain pipeline sections.