Pipeline Safety: Identification and Evaluation of Potential Hard Spots-In-Line Inspection Tools and Analysis

<NOTICE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Pipeline and Hazardous Materials Safety Administration</SUBAGY> <DEPDOC>[Docket No. PHMSA-2024-0176]</DEPDOC> <SUBJECT>Pipeline Safety: Identification and Evaluation of Potential Hard Spots—In-Line Inspection Tools and Analysis</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Pipeline and Hazardous Materials Safety Administration (PHMSA), Department of Transportation. <HD SOURCE="HED">ACTION:</HD> Notice; issuance of advisory bulletin. <SUM> <HD SOURCE="HED">SUMMARY:</HD> PHMSA is issuing this advisory bulletin to notify pipeline owners and operators of the importance of evaluating their pipeline facilities for the existence and potential threat of hard spots in the pipe body. That susceptibility comes from the plate and pipe manufacturing and is broader than previously understood; recent data and incident investigations indicate that hard spots could affect multiple pipelines manufactured prior to 1970. Hard spots, if not identified and mitigated, pose a threat to the integrity of the pipeline from interacting threats such as coating degradation, soil chemistry, and/or increased hydrogen exposure, which can result in hydrogen-induced cracking. Pipeline owners and operators should consider expanding their hard spot threat evaluation to all pipe manufactured prior to 1970, regardless of manufacturer; collecting and analyzing data associated with hard spot magnetic flux leakage in-line inspection tools; and following industry best practices when conducting in-line inspection data analysis. </SUM> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Max Kieba, Director, Engineering & Research Division, at 202-420-9169 or <E T="03">Max.Kieba@dot.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">I. Background</HD> The purpose of this advisory bulletin is to notify owners and operators of gas, hazardous liquid, and carbon dioxide pipelines of the importance of evaluating their pipeline facilities for the existence and potential threat of hard spots in the pipe body. A major tenet of PHMSA's pipeline safety oversight program is that pipeline operators must know and understand their pipeline systems, and use appropriate technologies and procedures to address risks to prevent pipeline failures while considering the inherent limitations of such technology. PHMSA prescribes factors that must be addressed to mitigate risk and conducts inspections to ensure adequate measures are carried out effectively. A hard spot is a defect that is created at the time the steel plates are rolled during the pipe manufacturing process. The creation of hard spots in manufacturing is not attached to the in-service product. Even where a pipe may have an intended service at the time of manufacture, the intended service may change after manufacture. A localized increase in hardness produced during the hot rolling of steel plates as a result of localized cooling can form a hard spot. Localized hardening may also occur through the unintentional quenching during the manufacturing process or by cold work. Although hard spots are more prevalent in plate-formed pipe, seamless pipe can also be susceptible to hard spots when poor controls in the manufacturing process result in material property variations, including hardness. <SU>1</SU> <FTREF/> <FTNT> <SU>1</SU>   <E T="03">See</E> Jeremy Faissat et al., “ <E T="03">Pipeline Hard Spots: How Hard is Hard?</E> ,” Pipeline Technology Conf. 2021 (Apr. 1, 2021), <E T="03">https://www.pipeline-conference.com/abstracts/pipeline-hard-spots-how-hard-hard; see also</E> Rosen Group, Presentation, “ <E T="03">Hard Spot Assessment & Integrity Analyses</E> ,” slide 6 (Dec. 13, 2022), <E T="03">https://primis-meetings.phmsa.dot.gov/archive/Day_1_AM_1050_Hard_Spot_Assessment_-_Integrity_Analysis.pdf</E> (National Tube pipe). </FTNT> Hardness can be measured in any condition, at any time, and is determined by measuring the depth of an indentation made by a calibrated indentation device. There are three industry standards that address hardness testing: (1) ASTM E92 Standard Test Methods for Vickers Hardness of Metallic Materials; (2) ASTM E10-18 Standard Test Methods for Brinell Hardness of Metallic Materials; and (3) ASTM E18-22 Standard Test Methods for Rockwell Harness of Metallic Materials. Hard spots found by in-line inspection (ILI) analysis can be verified through the use of calibrated devices that press a specific tool into the plate's surface and then measure the resulting width or depth of the indentation. <SU>2</SU> <FTREF/> American Petroleum Institute (API) Specification 5L states that “[a]ny hard spot larger than 50 mm (2.0 in) in any direction shall be classified as a defect if its hardness exceeds 35 HRC, 345 HV10 or 327 HBW, based upon individual indentations.”  <E T="51">3 4</E> <FTREF/> However, recent improvements in technology have revealed incidents on hard spots with lower hardness measures. <FTNT> <SU>2</SU>  The three hardness units—HRC, HB and HV <E T="52">10</E> —can be converted using a standard conversion table. </FTNT> <FTNT> <SU>3</SU>  API Specification 5L, “Specification for Line Pipe,” section 9.10.6, (46th ed., Apr. 2018) (incorporated by reference under 49 CFR 192.7 and 195.3). <SU>4</SU>  49 CFR 192.3 defines a “hard spot” as “an area on steel pipe material with a minimum dimension greater than two inches (50.8 mm) in any direction and hardness greater than or equal to Rockwell 35 HRC (Brinell 327 HB or Vickers 345 HV <E T="52">10</E> ).” </FTNT> Hard spots generally form on the surface of pipe and, by themselves, can be considered a stable threat. Unfortunately, hard spots can become unstable when the threat is activated by a change in service conditions such as coating degradation, effects of soil chemistry, and/or influence of the cathodic protection hydrogen film. The presence of hydrogen can result in hydrogen-induced cracking due to hydrogen accumulation at inclusions, impurities, and lattice structure irregularities in the presence of stress on the steel ( <E T="03">e.g.,</E> from operating pressures). Typically, coatings insulate hard spots from exposure to hydrogen generated by the cathodic protection system, but coatings can deteriorate over time. Recent Pipeline Research Council International (PRCI) research indicates that the level of cathodic protection may also contribute to hydrogen cracking. <SU>5</SU> <FTREF/> <FTNT> <SU>5</SU>  Zoe H. Shall, Presentation, “ <E T="03">PRCI Efforts on Hard Spots: Past, Present, and Future,</E> ” slide 15 (Dec. 13, 2022), <E T="03">https://primis-meetings.phmsa.dot.gov/archive/Day_1_AM_1020_PRCI_Efforts_on_Hard_Spots_Dec_2022.pdf.</E> </FTNT> PHMSA has previously discussed, in public meetings and workshops, the threat evaluations of pipelines constructed with pipe manufactured by A.O. Smith Corporation (A.O. Smith) from 1948 through 1952 due to the pipe's susceptibility to hard spot related hydrogen cracking. <SU>6</SU> <FTREF/> In the past 20 years, the following five incidents highlight hydrogen-induced cracking of hard spots. All but one of the incidents occurred on pipe manufactured by A.O. Smith. <FTNT> <SU>6</SU>  Gery Bauman & Mary McDaniel, Presentation, “Recent Case Study hard Spts and NTSB Recommendation P-22-3,” slide 20 (Dec. 13, 2022), <E T="03">https://primis-meetings.phmsa.dot.gov/archive/MtgHome.mtg@mtg=161.html; see generally,</E> PHMSA, “Class Location Special Permits: FAQs,” FAQ 34 (June 16, 2010) (providing that hard spots are a safety condition that may reduce the toughness of pipe body), <E T="03">https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fwww.phmsa.dot.gov%2Fsites%2Fphmsa.dot.gov%2Ffiles%2Fdocs%2Ftechnical-resources%2Fpipeline%2Fclass-location-special-permits%2F64051%2Ffaqsclass-location-special-permits20180726.docx&wdOrigin=BROWSELINK.</E> </FTNT> • On July 18, 2013, a 30-inch natural gas pipeline ruptured in Natchitoches, Louisiana. The pipe was manufactured in 1952 by A.O. Smith. Evidence suggested the failure was caused by hydrogen-induced cracking in a hard spot that was previously reinforced with a Type A sleeve. The leak, in this instance, was repaired with a Type B sleeve. • On January 14, 2015, a 30-inch natural gas pipeline ruptured in Brandon, Mississippi. The pipe was manufactured in 1952 by A.O. Smith. The failure was caused by hydrogen-induced cracking in a hard spot greater than two inches in length, previously reinforced with a Type A sleeve. Hardness testing could not be performed with the sleeve in place. • On August 1, 2019, a 30-inch natural gas pipeline ruptured in Danville, Kentucky. The pipe was manufactured in 1957 by A.O. Smith. The failure was caused by hydrogen-induced cracking in a hard spot. Hardness testing by the National Transportation Safety Board (NTSB) identified the origin hard spot was 5.85 inches by 3 inches, and had hardness values between 362 and 381 Brinell. Hardness readings extended through the pipe wall. • On February 13, 2022, an 18-inch natural gas pipeline ruptured in Perry County, Mississippi. The pipe was manufactured in 1950 by A.O. Smith. The failure was caused by hydrogen-induced cracking in a hard spot. Metallurgical testing found hardness values between 35 to 45 Rockwell, and was measured at approximately 0.6-inch by 2.5-inch. • On March 8, 2023, a 30-inch natural gas pipeline ruptured in Fauquier County, Virginia. The pipe was manufactured in 1957 by Bethlehem Steel. The failure was caused by hydrogen-induced cracking in a hard spot. Post incident ILI identified six hard spot features, and hardness values were confirmed from four features that ranged from 192-208 Brinell, which was slightly harder than base hardness (approximately 170 to 180 Brinell). In this instance, the operato ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 18k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━