ASME B31G-2012 pdf download

ASME B31G-2012 pdf download.Manual for Determining the Remaining Strength of Corroded Pipelines.
(b) Flow stress is a conceptrelevanttofracture mechan- ics and is used in the Level 1, Level 2, and Level 3 evaluations. It is not a property specified in a material grade or finished product standard. Research indicates that it may be defined variously as given below. (1) S flow forplaincarbon steel operatingattempera- tures below 250°F (120°C) may be defined by S flow p 1.1 ? SMYS. S flow shall not exceed SMTS. (2) S flow for plain carbon and low-alloy steel having SMYS not in excess of 70 ksi (483 MPa) and operating at temperatures below 250°F (120°C) may be defined by S flow p SMYS + 10 ksi (69 MPa). S flow shall not exceed SMTS. (3) S flow for plain carbon and low-alloy steel having SMYS not in excess of 80 ksi (551 MPa) may be defined by S flow p (S YT + S UT )/2, where S YT and S UT are specified at the operating temperature in accordance with the ASME Boiler and Pressure Vessel Code, Section II, Part D; applicable pipe product specification; or room temperature strength multiplied by the temperature derating factor specified by the applicable construction code. Linear interpolation of strength values is allowed between listed temperatures. (c) This documentdoes notprescribewhichdefinition for flow stress should be used where more than one definition applies. Where more than one definition applies, the various definitions produce acceptable though not necessarily identical results when used with any given evaluation method. It is noted that S flow was defined as 1.1 ? SMYS inprevious editions ofB31G. This definition remains an inherent element of the Level 0 assessment and is recommended with the Level 1 assess- ment performed in accordance with para. 2.2(a). (d) Only the specified nominal wall thickness shall be used for the uncorroded wall thickness when con- ducting a Level 0 evaluation. If known with confidence, the actual uncorroded wall thickness may be used with a Level 1, Level 2, or Level 3 evaluation, with a suitable adjustment of the hoop stress due to internal pressure. (e) Pipe body material may be considered to have adequate ductile fracture initiation properties for pur- poses of this Standard if the material operates at a tem- perature no colder than 100°F (55°C) below the temperature at which 85% shear appearance is observed in a Charpy V-notched impact test. (f) Electric resistance welded (ERW) seams that have been subjected to a normalizing heat treatment, single and double submerged arc welded seams, and girth welds made using the shielded metal arc, gas metal arc, flux cored arc, and submerged arc processes (manual or 3 automated, and in any combination) are considered to have adequate ductile fracture initiation properties for purposes of this Standard. Other seam and weld types shall be investigated to establish fracture properties before applying methods described herein to metal loss affecting such welds. Consideration shall be given to the disposition of workmanship flaws or manufacturing flaws within a weld or seam that could interact with metal loss due to corrosion. (g) Some operating conditions, such as low- temperature service, or long-term exposure to sour envi- ronments or to very high temperatures, could adversely affect the ductility and fracture toughness properties of some materials. It is the user’s responsibility to consider such conditions where necessary before applying meth- ods described herein. 1.8 Evaluation Procedure Evaluations shall be carried out in accordance with the procedures described in section 2. In addition, the following considerations apply: (a) Units may be in any self-consistent system. It is the responsibility of the user to determine unitary con- version factors as may be required. (b) This document makes no recommendation as to which evaluation level and evaluation method to select. All methods described herein have been demonstrated to provide reliable and conservative results when they are applied correctly and within stated limitations. Not allmethods give identicalnumerical results or consistent degrees of conservatism. It is the pipeline operator’s responsibility to select an evaluation method, based on experience and judgment, that is consistent with its operating procedures. (c) Original source reference documents for each methodology are cited. Further references may be found in other documents available in the public domain. While each method can be applied as presented, source documents may provide additional information to the user. The user should consider referring to applicable sources as necessary in order to best implement a given method. (d) Other evaluation methods may evolve or come into use which were not contemplated by this document. It is not the intention of this document to prohibit their use, butthe user ofsuchmethods shall be able to demon- strate that the objective of a safe and reliable assessment of metal loss can be achieved. 1.9 Safety Factors and the Meaning of Acceptance A flaw or anomaly is considered acceptable where the computed failure stress is equal to or greater than the hoop stress at the operating pressure multiplied by a suitable safety factor. There is no single safety factor that is suitable for all types of pipeline construction, for all modes of pipeline operation, or for all types of flaws or anomalies.