{"operation":"document","citation":"PI-22-0006","title":"CH-IV Regulatory — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2022-05-25","effective_on":null,"summary":"PI-22-0006 response to CH-IV Regulatory concerning 193.2167.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-22-0006.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-22-0006.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-22-0006","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/pipeline/interpretations/76511/ch-iv-pi-22-0006-5-24-2022-part1932167.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nMay 24, 2022\nMr. Juan Carlos Rivadeneira\nCH-IV\n11700 Katy Freeway\nSuite 1350\nHouston, TX 77079\nDear Mr. Rivadeneira:\nIn a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA), dated\nFebruary 28, 2022, you requested an interpretation of the federal pipeline safety regulations in\n49 Code of Federal Regulations (CFR) Part 193 with respect to the applicability of § 193.2167 to\nburied liquefied natural gas (LNG) piping systems.\nIn your letter you quoted the applicable provisions for enclosed impounding systems found in the\npipeline safety regulations, and the 2001 and 2019 editions of the National Fire Protection\nAssociation 59A Standard for the Production, Storage, and Handling of Liquefied Natural Gas\n(NFPA 59A-20011 and NFPA 59A-20192, respectively). You noted that § 193.2167, NFPA\n59A-2001, and NFPA 59A-2019 all recognize the hazards involved with the use of enclosed\nLNG impoundment systems and, therefore, prohibit the use of such systems or provide specific\nrequirements for the safe design of such systems. You explained that enclosed LNG impounding\nsystems can result in confined vapor explosions resulting from the mixture of LNG vapors and\noxygen from the atmosphere. You opined that the prohibition on the use of covered impounding\nsystems in § 193.2167 was to reduce the risk of confined vapor explosions due to the mixture of\nLNG vapors with air in enclosed volumes.\nTherefore, you reasoned that § 193.2167 should only be applied to covered impoundment\nsystems where air is expected or can be present under normal operating conditions. You asserted\nthat buried LNG piping is not open to the atmosphere and does not have empty voids in between\nthe piping and soil where LNG vapors from a leak could concentrate with ambient air leading to\na confined vapor explosion. You stated that even if LNG or LNG vapors were to surface to\ngrade, the LNG would then be unconfined and would not result in the kind of vapor explosion\n§ 193.2167 was designed to prevent.\n1 Incorporated by reference into Part 193. See, § 193.2013(g)(1)).\n2 NFPA 59A-2019 is not incorporated by reference into Part 193.\nThe Pipeline and Hazardous Materials Safety Administration, Office of Pipeline Safety provides written clarifications of the Regulations (49 CFR\nParts 190-199) in the form of interpretation letters. These letters reflect the agency's current application of the regulations to the specific facts\npresented by the person requesting the clarification. Interpretations are not generally applicable, do not create legally-enforceable rights or\nobligations, and are provided to help the specific requestor understand how to comply with the regulations.\n\n<<<PAGE 2>>>\n\n2\nAsserting the same line of reasoning, you argued that a buried LNG pipeline surrounded\ncompletely by soil with a concrete slab directly placed on top of the soil, such as a buried piping\ninstallation crossing a road, is also not an enclosed impoundment system. As you explained, in\nthis scenario, there is no empty void in between the soil and concrete slab that is open to\natmosphere where ambient air and LNG vapors can form an explosive mixture in a confined\nvolume.\nYou further contended that for a buried pipeline to become a closed impoundment system such\nas those prohibited by § 193.2167, the soil impoundment over the pipeline, exposed to the\natmosphere, would need to be covered or congested in such a manner that LNG vapors could\nmix with ambient air in a confined or congested volume. You explained that for LNG vacuum\njacketed piping, the soil surrounding the outer jacket will also serve as the impoundment system\nwhere 1) the outer pipe is not used for LNG impoundment, and 2) where the vacuum jacketed\npipe does not affect the prescribed design spills, impoundment determinations, or other hazard\ncalculations.\nConcluding, based on the inherent differences between an enclosed impoundment system and\nburied piping, you asked if § 193.2167 applies to buried LNG piping.\nPart 193 prescribes safety standards for LNG facilities used in the transportation of gas by a\npipeline that is subject to the pipeline safety laws (49 U.S.C. 60101 et seq.) and Part 192 of this\nchapter. See § 193.2001(a). Section 193.2167 is specifically found in Subpart C, Design, of Part\n193, which incorporates by reference NFPA 59A–2001. See § 193.2101. If there is a conflict\nbetween Part 193 and NFPA 59A–2001, the requirements in Part 193 prevail.\nThe applicable definitions and requirements in 49 CFR Part 193 and NFPA 59A-2001 are as\nfollows:\n§ 193.2007 - Definitions.\nImpounding space means a volume of space formed by dikes and floors which is\ndesigned to confine a spill of hazardous liquid.\nImpounding system includes an impounding space, including dikes and floors for\nconducting the flow of spilled hazardous liquids to an impounding space.\n§ 193.2167 Covered systems.\nA covered impounding system is prohibited except for concrete wall designed tanks\nwhere the concrete wall is an outer wall serving as a dike.\nNFPA 59A-2001 Section 2.2.2.3\nEnclosed drainage channels for LNG shall be prohibited.\nThe Pipeline and Hazardous Materials Safety Administration, Office of Pipeline Safety provides written clarifications of the Regulations (49 CFR\nParts 190-199) in the form of interpretation letters. These letters reflect the agency's current application of the regulations to the specific facts\npresented by the person requesting the clarification. Interpretations are not generally applicable, do not create legally-enforceable rights or\nobligations, and are provided to help the specific requestor understand how to comply with the regulations.\n\n<<<PAGE 3>>>\n\n3\nException: Container downcomers used to rapidly conduct spilled LNG away from\ncritical areas shall be permitted to be enclosed if they are sized for the anticipated liquid\nflow and vapor formation rates.\nPart 193 does not require buried LNG piping to have an impoundment system. However, if an\noperator has an impoundment system, pursuant to § 193.2167 a covered impounding system is\nprohibited except for concrete wall designed tanks where the concrete wall is an outer wall\nserving as a dike. This requirement applies to all impoundment systems without consideration of\natmospheric exposure. Therefore, a buried LNG piping system with a covered impoundment\nsystem or vacuum jacketed piping, where the secondary pipe serves as the impoundment system,\nis prohibited under § 193.2167.\nIf an operator desires to have buried LNG piping with a covered impoundment system or\nvacuum jacketed piping, the operator may seek a special permit to deviate from the prohibition\nagainst covered impoundment systems in § 193.2167.\nIf we can be of further assistance, please contact Tewabe Asebe at 202-366-5523.\nSincerely,\nJohn A. Gale\nDirector, Office of Standards\nand Rulemaking\nThe Pipeline and Hazardous Materials Safety Administration, Office of Pipeline Safety provides written clarifications of the Regulations (49 CFR\nParts 190-199) in the form of interpretation letters. These letters reflect the agency's current application of the regulations to the specific facts\npresented by the person requesting the clarification. Interpretations are not generally applicable, do not create legally-enforceable rights or\nobligations, and are provided to help the specific requestor understand how to comply with the regulations.\n\n<<<PAGE 4>>>\n\nContact Name: Juan Carlos Rivadeneira Title: Engineer\nDirect Line: 713-964-6775\nDirect Email: jcrivadeneira@ch-iv.com\n11700 Katy Freeway, Suite 1350\nHouston, TX 77079 USA\nwww.CH-IV.com\nFebruary 28, 2022\nMr. John A. Gale\nDirector, Office of Standards and Rulemaking\nOffice of Pipeline Safety (PHP-30)\nPipeline and Hazardous Materials Safety Administration\nU.S. Department of Transportation\n1200 New Jersey Avenue, S.E.\nWashington, D.C. 20590-0001\nRequest for Interpretation of 49 CFR §193.2167\nDear Mr. Gale,\nThis letter is a formal request for written interpretation from the Pipeline and Hazardous Materials\nSafety Administration of Title 49 Code of Federal Regulations Part 193. This interpretation is\nrequested to clarify the intent and applicability of §193.2167 to buried liquefied natural gas (“LNG”)\npiping systems.\n§193.2167 states that:\nA covered impounding system is prohibited except for concrete wall designed\ntanks where the concrete wall is an outer wall serving as a dike.\nSimilarly, the National Fire Protection Association 59A Standard for the Production, Storage, and\nHandling of Liquefied Natural Gas (“NFPA 59A”) 2001 edition (“NFPA 59A-2001”), Chapter 2.2\nprovides requirements regarding the use of enclosed LNG drainage channels. NFPA 59A-2001\nSection 2.2.2.3 states:\nEnclosed drainage channels for LNG shall be prohibited.\nException: Container downcomers used to rapidly conduct spilled LNG away from\ncritical areas shall be permitted to be enclosed if they are sized for the anticipated\nliquid flow and vapor formation rates.\nAlthough not considered by Part 193, the 2019 edition of NFPA 59A (“NFPA 59A-2019”), Chapter\n13, provides specific requirements for installation of enclosed impounding systems. NFPA 59A-\n2019, Section 13.5 states that:\n1 of 3\n\n<<<PAGE 5>>>\n\nEnclosed impounding systems for piping shall be prohibited except for where\nthey met one of the following conditions:\n(1) The system is sealed from the atmosphere, filled with an inert gas, and\ninstrumentation and controls are provided to maintain pressures at a safe\nlevel and to monitor gas concentrations.\n(2) Pipe-in-pipe is installed in accordance with 10.13.3.2.\nNFPA 59A-2019, Section 10.13.3.2, states that:\nIf the outer pipe also functions as the secondary containment system, the following\nshall apply:\n(1) The outer pipe shall be designed to contain the inner pipe product upon any\nrelease from the inner pipe.\n(2) The outer pipe shall be designed, fabricated, examined, and tested in\naccordance with the requirements of ASME B31.3, Process Piping.\n(3) The outer pipe shall include a stress analysis of the mechanical forces and\nthermal shock upon a release from the inner pipe.\n§193.2167, NFPA 59A-2001 and NFPA 59A-2019, all recognize the hazards involved with the\nuse of enclosed LNG impoundment systems and therefore, prohibit the use of such systems or\nprovide specific requirements for the safe design of such systems. Enclosed LNG impounding\nsystems can result in confined vapor explosions resulting from the mixture of LNG vapors and\noxygen from the atmosphere. This hazard is clearly recognized by the design requirements in\nNFPA 59A-2019, Section 13.5, which specifically address the need to prevent air ingress to the\nenclosed impounding system, eliminating the risk of confined vapor explosions as the LNG vapors\nbecome an ignitable mixture when ambient air is present. Two industry examples where LNG\nvapor (natural gas) leaked into confined spaces and formed an explosive mixture with air include:\n(1) The October 1944 East Ohio Gas Company incident where LNG from a failed storage tank\nspilled onto residential streets and storm sewer systems resulting in a fire and explosions\nwithin the sewer system.\n(2) The 1978 Cove Point LNG Receiving Terminal incident where LNG leaked through an\ninadequately tightened LNG pump electrical penetration seal, vaporized, passed through\n200 feet of underground electrical conduit and entered the substation. The natural gas-\nair mixture within the substation was ignited, resulting in a confined explosion.\nConsistent with LNG industry codes and safe practices, §193.2167 prohibits the use of covered\nimpounding systems to reduce the risk of confined vapor explosions due to the mixture of LNG\nvapors with air in enclosed volumes. Therefore, §193.2167 should only be applied to covered\nimpoundment systems where air is expected or can be present under normal operating\nconditions, for example, an aboveground LNG trench with a cover or an underground drainage\nsystem that is open to atmosphere.\nA buried LNG pipeline is not open to the atmosphere and does not have empty voids in between\nthe pipeline and soil where LNG vapors from a leak could concentrate with ambient air leading to\na confined vapor explosion. Even if LNG or LNG vapors would surface to grade, the hazardous\nfluid would then be unconfined and would not result in a vapor explosion (where no congestion is\npresent above the area) such as that prevented by §193.2167.\n2 of 3\n\n<<<PAGE 6>>>\n\nSimilarly, a buried pipeline surrounded completely by soil with a concrete slab directly placed on\ntop of the soil, such as a buried pipeline installation crossing a road, is not an enclosed\nimpoundment system, as there is no empty void in between the soil and concrete slab that is open\nto atmosphere where ambient air and LNG vapors can form an explosive mixture in a confined\nvolume.\nFurthermore, §193.2007 defines an Impounding Space as:\na volume of space formed by dikes and floors which is designed to confine a spill\nof hazardous liquid.\nOn a buried LNG pipeline, the soil surrounding the pipeline provides the volume of space to\nconfine the spill. A pipeline that has a leak or has failed cannot provide containment to itself; it is\nthe soil around the pipeline that confines the spill. For a buried pipeline to become a closed\nimpoundment system such as those prohibited by §193.2167, the soil (impoundment) over the\npipeline, exposed to atmosphere, would need to be covered or congested in such a manner that\nLNG vapors could mix with ambient air in a confined or congested volume. For example, a buried\nLNG pipeline routed along a congested process area or inside a building.\nFor buried LNG vacuum jacketed piping, the soil surrounding the outer jacket will also serve as\nthe impoundment system where:\na) the outer pipe is not used for LNG impoundment, and\nb) where the vacuum jacketed pipe does not affect the prescribed design spills,\nimpoundment determinations, or other hazard calculations.1\nFor the same reasons described above, this impoundment system is not “covered” as prohibited\nby §193.2167.\nBased on the hazard prevented by §193.2167 and NFPA 59A, and the inherent differences\nbetween an enclosed impoundment system that could lead to a confined explosion and a buried\npipeline, we would like to confirm that §193.2167 does not apply to buried LNG pipeline\ninstallations such as those described in this interpretation request.\nI am available for future discussions as needed. Thank you for your assistance and I look forward\nto hearing from you soon.\nJUAN CARLOS RIVADENEIRA\nEngineer\n1 See PHMSA, LNG Plant Requirements: Frequently Asked Questions, D4, (last updated: October 23,\n2017). available at: https://www.phmsa.dot.gov/pipeline/liquified-natural-gas/lng-plant-requirements-\nfrequently-asked-questions.\n3 of 3","truncated":false,"body_characters":14887}