ASME B31G-2009 pdf download.Manual for Determining the Remaining Strength of Corroded Pipelines.
1 INTRODUCTION 1.1 Scope This document is intended solely for the purpose of providing guidance in the evaluation of metal loss in pressurized pipelines and piping systems. It is applica- ble to all pipelines and piping systems within the scope of the transportation pipeline codes that are part of ASME B31 Code for Pressure Piping, namely: ASME B31.4, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids; ASME B31.8, Gas Transmission and Distribution Piping Systems; ASME B31.11, Slurry Transportation Piping Systems; and ASME B31.12, Hydrogen Piping and Pipelines, Part PL. Where the term pipeline is used, it may also be read to apply to piping or pipe conforming to the acceptable applications and within the technical limitations dis- cussed below. 1.2 Acceptable Applications The application of this document is limited to the evaluationofwallloss inmetal pipewithinthe following limitations: (a) metal loss in pipelines located below ground, above ground, or offshore (b) metal loss due to external or internal corrosion (c) metal loss produced by grinding where used to completely remove mechanical damage, cracks, arc burns, manufacturing defects, or other defects from the pipe surface (d) metal loss in field bends, induction bends, and elbows (e) metal loss that incidentally affects longitudinal or helical electric seam welds or circumferential electric welds of sound quality and having ductile characteris- tics, provided workmanship flaws are not present in sufficiently close proximity to interact with the metal loss (f) metal loss of any depth with respect to the pipe wall, except that due consideration shall be given to the accuracy of measurements and effective corrosion rates when the depth of metal loss exceeds 80% of the actual pipe wall dimension (g) metal loss in new pipe where allowed bythe appli- cable code of construction
(h) metal loss in pipe material having ductile fracture initiation characteristics [see paras. 1.7(e) and (f)] unless using a Level 3 assessment in accordance with paras. 2.2(b) and 2.3 (i) metal loss in pipe operating at temperatures above ambient within the range of operating temperature rec- ognized by the governing standard, and provided mate- rial strength properties at temperature are considered (j) metal loss in pipe operating at any level of allow- able design hoop stress [see paras. 1.4(a) and (b) for additional considerations] (k) metal loss in pipe where internal pressure is the primary loading [see paras. 1.4(c) and (d) for additional considerations] 1.3 Exclusions This document does not apply to the following: (a) crack-like defects or mechanical surface damage not completely removed to a smooth contour by grinding (b) metal loss in indentations or buckles resulting in radial distortion of the pipe wall larger than 6% of the pipe outside diameter, unless a Level 3 assessment is performed in accordance with para. 2.3 (c) grooving corrosion, selective corrosion, or prefer- ential corrosion affecting pipe seams or girth welds (d) metal loss in fittings other than bends or elbows (e) metal loss affecting material having brittle fracture initiation characteristics [see paras. 1.7(e) and (f)] unless a Level 3 assessment is performed in accordance with para. 2.4 (f) pipe operating at temperatures outside the range of operating temperature recognized by the governing standard or operating at temperatures in the creep range 1.4 Additional Considerations The user is cautioned that additional considerations may apply in certain situations, described below. (a) Pipe operating at low hoop stress levels due to internal pressure (e.g., less than 25% of SMYS) may be perforated by corrosion without inducing structural material failure. The methods and criteria provided herein do not address failure by perforation.