ASME B31G:2009 pdf download

ASME B31G:2009 pdf download Manual for Determining the Remaining Strength of Corroded Pipelines
confidence to warrant their usage,may be used withLevel 3 evaluations. Statistical representations of mate-rial properties may be used with Levels 1,2, or 3 forpurpose of establishing a probability of failure; however,the details of such analyses are outside the scope of thisdocument.
(b) Flow sfress is a concept relevant to fracture mechan-ics and is used in the Level 1,Level 2, and Level 3evaluations. It is not a property specified in a materialgrade or finished product standard. Research indicatesthat it may be defined variously as given below.
(1)Saos for plain carbon steel operating at tempera-tures below 250°F (120°C) may be defined by Shlowe=1.1 × SMYS.Snow shall not exceed SMTS.
(2) Sflcow. for plain carbon and low-alloy steel havingSMYS not in excess of 70 ksi (483 MPa) and operatingat temperatures below 250°F (120°C) may be defined byShlow = SMYS + 10 ksi (69 MPa). Snow shall not exceedSMTS.
(3)Saow for plain carbon and low-alloy steel havingSMYS not in excess of 80 ksi (551 MPa) may be definedby Snow =(Syr+Surr)/ 2, where Sy and Surare specifiedat the operating temperature in accordance with theASME Boiler and Pressure Vessel Code, Section II, PartD; applicable pipe product specification; or room tem-perature strength multiplied by the temperature derat-ing factor specified by the applicable construction code.Linear interpolation of strength values is allowedbetween listed temperatures.
(c) This document does not prescribe which definitionfor flow stress should be used where more than onedefinition applies. Where more than one definitionapplies, the various definitions produce acceptablethough not necessarily identical results when used withany given evaluation method. It is noted that Sfow wasdefined as 1.1 ×SMYSin previous editions of B31G.Thisdefinition remains an inherent element of the Level 0assessment and is recommended with the Level 1 assess-ment performed in accordance with para. 2.2(a).
(d)Only the specified nominal wall thickness shallbe 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 witha Level 1, Level 2, or Level 3 evaluation, with a suitableadjustment of the hoop stress due to internal pressure.(e) Pipe body material may be considered to haveadequate ductile fracture initiation properties for pur-poses of this Standard if the material operates at a tem-perature no colder than 100°F (55C) below thetemperature at which 85% shear appearance is observedin a Charpy V-notched impact test.
(f》Electric resistance welded(ERW) seams that havebeen subjected to a normalizing heat treatment, singleand double submerged arc welded seams, and girthwelds made using the shielded metal arc, gas metal arc,flux cored arc, and submerged arc processes (manual or automated, and in any combination) are considered tohave adequate ductile fracture initiation properties forpurposes of this Standard.Other seam and weld typesshail be investigated to establish fracture propertiesbefore applying methods described herein to metal lossaffecting such welds. Consideration shall be given tothe disposition of workmanship flaws or manufacturingflaws within a weld or seam that could interact withmetal 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 adverselyaffect the ductility and fracture toughness properties ofsome materials. It is the user’s responsibility to considersuch conditions where necessary before applying meth-ods described herein.
1.8Evaluation Procedure
Evaluations shall be carried out in accordance withthe procedures described in section 2.In addition, thefollowing considerations apply:
(a) Units may be in any self-consistent system. It isthe responsibility of the user to determine unitary con-version factors as may be required.
(b)This document makes no recommendation as towhich evaluation level and evaluation method to select.All methods described herein have been demonstratedto provide reliable and conservative results when theyare applied correctly and within stated limitations. Notall methods give identical numerical results or consistentdegrees of conservatism. It is the pipeline operator’sresponsibility to select an evaluation method, based onexperience and judgment, that is consistent with itsoperating procedures.
ic) Original source reference documents for eachmethodology are cited.Further references may be foundin other documents available in the public domain.wWhile each method can be applied as presented, sourcedocuments may provide additional information to theuser. The user should consider referring to applicablesources as necessary in order to best implement a givenmethod.
d) Other evaluation methods may evolve or comeinto use which were not contemplated by this document.It is not the intention of this document to prohibit theiruse,but the user of such methods shall be able to demon-strate that the objective of a safe and reliable assessmentof metal loss can be achieved.
1.9 Safety Factors and the Meaning of AcceptanceA flaw or anomaly is considered acceptable wherethe computed failure stress is equal to or greater thanthe hoop stress at the operating pressure multiplied bya suitable safety factor. There is no single safety factorthat is suitable for all types of pipeline construction, forall modes of pipeline operation, or for all types of flawsor anomalies.