ASME B31G:2009 pdf free download

ASME B31G:2009 pdf free download.Manual for Determining the Remaining Strength of Corroded Pipelines.
(h) metal loss in pipe material having ductile fracture initiation characteristics Isee paras. 1.7(e) and (1)1 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 recognized by the governing standard, and provided material strength properties at temperature are considered
(j) metal loss in pipe operating at any level of allowable design hoop stress Isee paras. 1.4(a) and (b) for additional cunsiderationsi
(k) metal loss in pipe where internal pressure is the primary loading Isee paras. 1.4(c) and (d) for additional considerationsl
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 preferential 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 Isee paras. 1.7(e) and (1)1 unless a Level 3 assessment is performed in accordance with para. 2.4
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 he perforated by corrosion without inducing structural material failure. The methods and criteria provided herein do not address failure by perforation.
(b) Pipe affected by general corrosion of the pipe wall (i.e., corrosion-caused wall loss over the entire pipe surface) effectively operates at a greater hoop stress
Metal-loss corrosion anomalies indicated by inline inspection may be evaluated by a Level I or level 2 evaluation method. The user is cautioned against overstating the precision of evaluations applied with flaw dimensions indicated by inline inspection without adequate calibration or verification of actual flaw sizes by investigations carried out in the field.
1.12 Flaw Interaction
The methods described herein are suitable for evaluating isolated areas of metal loss. Corrosion may occur such that multiple areas of metal loss are closely spaced longitudinally or transversely. If spaced sufficiently closely, the metal loss areas may interact so as to result in failure at a lower pressure than would be expected based on an analysis of the separate flaws. The following guideline is suggested with reference to Fig. 1.12-1, based on limited testing and analysis:
(a) Flaws are considered interacting if they are spaced longitudinally or circumferentially from each other within a distance of 3 times the wall thickness (3t). Interacting flaws should be evaluated as a single flaw combined from all interacting flaws.
(b) Flaws are considered noninteracting if spaced outside of the above dimensions. Noninteracting flaws should be evaluated as separate flaws.
Care should be exercised when grouping or clustering anomalies indicated by inline inspection for purposes of evaluating interaction during the prioritization process. Consideration should be given to minimum thresholds of metal loss for reliable detection and sizing, minimum thresholds for reporting, and the expected mode of coating failure (e.g., localized failure versus disbondment over large areas). Methods employed for clustering of inline inspection anomalies should be validated by field verification of actual flaw dimensions and spacing.
1.13 Flaw Orientation
Corrosion caused by disbondment of continuous wrapped coatings may exhibit a helical pattern. If the helical pattern lies at an angle less than 45 deg to the pipe axis, the overall length of the corroded area indicated as L1 in Fig. 1.13-1 shall be considered in the evaluation. If the helical pattern lies at an angle of 45 deg or greater to the pipe axis, it is sufficient to consider the most severe longitudinal section through the corroded area having a length L2 in Fig. 1.13-1.