{"operation":"document","citation":"PI-25-0003","title":"Matrix PDM Engineering — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2024-10-23","effective_on":null,"summary":"PI-25-0003 response to Matrix PDM Engineering concerning 193.2007, 193.2013, 193.2401.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-25-0003.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-25-0003.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-25-0003","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-11/Matrix-PDM-PI-25-0003-10-23-2024-NFPA-59A-combined.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nOctober 21, 2025\nMr. Harry C. Parker, PE\nMechanical Supervisor\nMatrix PDM Engineering\n100 Beecham Drive, Suite 200\nPittsburg, PA 15205\nDear Mr. Parker:\nIn a letter dated October 23, 2024, Matrix PDM Engineering (Matrix PDM) requested a written\nregulatory interpretation from the Pipeline and Hazardous Materials Safety Administration’s\n(PHMSA) Office of Pipeline Safety (OPS) regarding the applicability of the liquefied natural gas\n(LNG) facilities safety standards in Title 49, Code of Federal Regulations (CFR) Part 193 to\n“pressure vessels” and “heat exchangers.” Specifically, Matrix PDM asked if pressure vessels or\nheat exchangers that do not contain any flammable, toxic, or corrosive gas or liquid are subject to\nthe regulations under 49 CFR Part 193 and the National Fire Protection Association’s Standard\nfor the Production, Storage, and Handling of Liquefied Natural Gas, 2001 edition (NFPA-59A-\n2001), as incorporated by reference in 49 CFR § 193.2013.\nBackground\nNFPA-59A-2001 sections 3.4.2 and 3.4.3 specify that boilers and pressure vessels (section 3.4.2)\nand shell and tube heat exchangers (section 3.4.3) must be designed and fabricated in accordance\nwith certain standards, such as ASME Boiler and Pressure Vessel Code (BPVC) Section VIII,\nDivision 1. Matrix PDM presented three questions regarding the applicability of NFPA-59A-\n2001 to specific boilers (pressure vessels) and shell and tube heat exchangers (heat exchangers)\nwithin a jurisdictional LNG plant (as defined in 49 CFR § 193.2007).\n• First, Matrix PDM asked if all pressure vessels and heat exchanges utilized in a\njurisdictional LNG plant are subject to NFPA-59A-2001, or only those that contain or\nutilize a hazardous fluid.\n• Second, Matrix PDM asked if the guidance in PHMSA’s LNG Frequently Asked\nQuestions (FAQ), questions D5 and D6, apply to “all” pressure vessels and heat\nexchangers, regardless of service.\n• Third, Matrix PDM asked if PHMSA fully adopts ASME BPVC Section VIII, Division 1,\nincluding paragraph U-1.\n\n<<<PAGE 2>>>\n\nMr. Harry C. Parker, PE\nPage 2\nRelevant Regulations\nOPS has determined the following regulations are relevant to Matrix PDM’s request for\ninterpretation:\n• 49 CFR § 193.2007 Definitions.\no Component means any part, or system of parts functioning as a unit, including,\nbut not limited to, piping, processing equipment, containers, control devices,\nimpounding systems, lighting, security devices, fire control equipment, and\ncommunication equipment, whose integrity or reliability is necessary to maintain\nsafety in controlling, processing, or containing a hazardous fluid.\no Gas, except when designated as inert, means natural gas, other flammable gas, or\ngas which is toxic or corrosive.\no Hazardous fluid means gas or hazardous liquid.\no Hazardous liquid means LNG or a liquid that is flammable or toxic.\no LNG facility means a pipeline facility that is used for liquefying natural gas or\nsynthetic gas or transferring, storing, or vaporizing liquefied natural gas.\no LNG plant means an LNG facility or system of LNG facilities functioning as a\nunit.\n• 49 CFR § 193.2401 Scope. After March 31, 2000, each new, replaced, relocated or\nsignificantly altered vaporization equipment, liquefaction equipment, and control systems\nmust be designed, fabricated, and installed in accordance with requirements of this part\nand of NFPA-59A-2001. In the event of a conflict between this part and NFPA 59A\n(incorporated by reference, see § 193.2013), this part prevails.\n• NFPA-59A-2001 Section 3.4.2. Boilers shall be designed and fabricated in accordance\nwith the ASME Boiler and Pressure Vessel Code, Section I, or CSA Standard B 51,\nBoiler, Pressure Vessel and Pressure Piping Code, and pressure vessels shall be designed\nand fabricated in accordance with the ASME Boiler and Pressure Vessel Code, Section\nVIII, Division 1 or Division 2, or CSA Standard B 51, Boiler, Pressure Vessel and\nPressure Piping Code, and shall be code-stamped.\n• NFPA-59A-2001 Section 3.4.3. Shell and tube heat exchangers shall be designed and\nfabricated in accordance with the standards of the Tubular Exchanger Manufacturers\nAssociation (TEMA). The shells and internals of all exchangers shall be pressure tested,\ninspected, and stamped in accordance with the ASME Boiler Pressure Vessel Code,\nSection VIII, Division 1 or Division 2, or CSA B51, where such components fall within\nthe jurisdiction of the pressure vessel code.\n• ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, 1992 Edition,\nSection U-1(c). The following classes of vessels are not considered to be within the\nscope of this Division:\no (1) those within the scope of other Sections;\no (2) fired process tubular heaters;\no (3) pressure containers which are integral parts or components of rotating or\nreciprocating mechanical devices, such as pumps, compressors, turbines,\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\nMr. Harry C. Parker, PE\nPage 3\ngenerators, engines, and hydraulic or pneumatic cylinders where the primary\ndesign considerations and/or stresses are derived from the functional requirements\nof the device;\no (4) except as covered in U-l(t), structures whose primary function is the transport\nof fluids from one location to another within a system of which it is an integral\npart, that is, piping systems;\no (5) piping components, such as pipe, flanges, bolting, gaskets, valves, expansion\njoints, fittings, and the pressure containing parts of other components, such as\nstrainers and devices which serve such purposes as mixing, separating, snubbing,\ndistributing, and metering or controlling flow, provided that pressure containing\nparts of such components are generally recognized as piping components or\naccessories;\no (6) a vessel for containing water under pressure, including those containing air,\nthe compression of which serves only as a cushion, when none of the following\nlimitations are exceeded: (a) a design pressure of 300 psi; (b) a design\ntemperature of 21 0°F.\no (7) a hot water supply storage tank heated by steam or any other indirect means\nwhen none of the following limitations is exceeded: (a) a heat input of 200,000\nBtu/hr; (b) a water temperature of 2l0°F; (c) a nominal water containing capacity\nof 120 gal;\no (8) vessels having an internal or external operating pressure (see 3-2) not\nexceeding 15 psi with no limitation on size [see UG-28(e)];\no (9) vessels having an inside diameter, width, height, or cross section diagonal not\nexceeding 6 in., with. no limitation on length of vessel or pressure;\no (10) pressure vessels for human occupancy.\n• LNG Plant Requirements: Frequently Asked Questions.\n1\nAnalysis\nEach new, replaced, relocated, or significantly altered vaporization equipment, liquefaction\nequipment, and control system must be designed, fabricated, and installed in accordance with the\nrequirements of Part 193 and of NFPA-59A-2001. 49 CFR § 193.2401. Boilers, pressure vessels,\nand shell and tube heat exchangers are types of equipment that may be used in vaporization and\nliquefaction. In addition, PHMSA has defined a “component” in 49 CFR § 193.2007 as any part,\nor system of parts functioning as a unit, including processing equipment and other equipment,\nwhose integrity or reliability is necessary to maintain safety in controlling, processing, or\ncontaining a hazardous fluid (e.g., gas or LNG). PHMSA has previously said that “[t]he term\n‘component’ has a very broad meaning in Part 193.” PHMSA Interpretation Response #PI-10-\n0020, p. 12, fn. 54 (Mar. 25, 2010).\n1 PHMSA, LNG Plant Requirements: Frequently Asked Questions,\nhttps://www.phmsa.dot.gov/pipeline/liquified-natural-gas/lng-plant-requirements-frequently-asked-questions (last\nupdated Aug. 19, 2025).\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\nMr. Harry C. Parker, PE\nPage 4\nIf any process or processing equipment, such as a boiler, pressure vessel, or heat exchanger, is\nnecessary to maintain safety when liquefying, storing, vaporizing, or transferring LNG, or\ncontrolling, processing, or containing a hazardous fluid, then it is a “component” and must be\ndesigned in accordance with 49 CFR Part 193 and NFPA-59A-2001, if replaced, relocated, or\nsignificantly altered after March 31, 2000, see 49 CFR § 193.2401.\nQuestion 1: In the context of NFPA-59A-2001, does the terms “pressure vessels” in section\n3.4.2 and “heat exchanger” in section 3.4.3 literally mean “all” pressure vessels and heat\nexchangers within an LNG plant, or just those that contain a hazardous fluid?\nPHMSA Response: NFPA-59A-2001 sections 3.4.2 and 3.4.3 apply to all boilers, pressure\nvessels, and shell and tube heat exchangers that are necessary to maintain safety when\nliquefying, storing, vaporizing, or transferring LNG, or controlling, processing, or containing a\nhazardous fluid.\nNFPA-59A-2001 sections 3.4.2 and 3.4.3 apply to certain pressure vessels or shell and tube heat\nexchangers that do not contain a hazardous fluid but are “necessary to maintain safety in\ncontrolling, processing, or containing a hazardous fluid” when liquefying, storing, vaporizing, or\ntransferring LNG (e.g., instrument air dryer tower vessels), liquefying natural gas (e.g., nitrogen\nstorage vessels), or vaporizing LNG (e.g., heating medium fluid expansion tanks).\nNFPA-59A-2001 sections 3.4.2 and 3.4.3 does not apply to certain pressure vessels or shell and\ntube heat exchangers that are not “necessary to maintain safety in controlling, processing, or\ncontaining a hazardous fluid” when liquefying, storing, vaporizing, or transferring LNG, such as\nthose used for utility services (e.g., a pressure vessel used in plant air system for running shop\ntools, storage of inert gases not connected to components, or similar utility use outside the\ncontrolling, processing, or containing of a hazardous fluid). NFPA-59A-2001 sections 3.4.2 and\n3.4.3 also does not apply to air-cooled heat exchangers because they are not shell and tube heat\nexchangers.\nQuestion 2: Does NFPA-59A-2001, section 1.2, as well as PHMSA LNG FAQs D5 and D6,\napply to all pressure vessels and heat exchangers within the LNG plant, regardless of service?\nPHMSA Response: All pressure vessels boilers, pressure vessels, and shell and tube heat\nexchangers that are necessary to maintain safety when liquefying, storing, vaporizing, or\ntransferring LNG, or controlling, processing, or containing a hazardous fluid are subject to 49\nCFR Part 193 and NFPA-59A-2001, and the associated LNG FAQs, including FAQs D5 and D6.\nQuestion 3: Does PHMSA fully adopt ASME BPVC, Section VIII, Division 1, paragraph U-1?\nPHMSA Response: PHMSA has incorporated by reference ASME BPVC, Section VIII,\nDivision 1 in its entirety (see 49 CFR § 193.2013). In the event of a conflict between 49 CFR\nPart 193 and NFPA-59A-2001 (and any technical standard incorporated by reference in NFPA-\n59A-2001, such as the ASME BPVC, Section VIII, Division 1), Part 193 prevails. For example,\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 5>>>\n\nMr. Harry C. Parker, PE\nPage 5\nif any of the pressure vessels and shell and tube heat exchangers fall within the classes of vessels\nin paragraph U-1 of the ASME BPVC, Section VIII, Division 1 but are a “component” as\ndefined in Part 193 that are “necessary to maintain safety in controlling, processing, or\ncontaining a hazardous fluid,” then they must be designed in accordance with 49 CFR §\n193.2401 and sections 3.4.2 and 3.4.3 in NFPA-59A-2001, and the associated LNG FAQs,\nincluding FAQs D5 and D6.\nIf we can be of further assistance, please contact Joseph Berry at (720) 601-3577.\nSincerely,\nJOHN A\nGALE\nDigitally signed by JOHN\nA GALE\nDate: 2025.10.30\n09:33:24 -04'00'\nJohn A. Gale\nDirector, Office of\nStandards and 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 6>>>\n\n25-0006\nPollack Move to hig r standard\nMATRlX P1DM\nENGINEERIN·G\nHarry C. Parker, PE\nMechanical Supervisor\nMatrix PDM Engineering\n100 Beecham Drive, Suite 200\nPittsburgh, PA 15205\n(412) 894-2270\nharryparker@Matrixpdm.com\nOctober 23, 2024\nAttn: Mr. Shane Kelley\nDirector, Standards and Rulemaktng Division\nU.S. DOT/PHMSA (PHH-10)\n1200 New Jersey Avenue\nSE East Building, 2nd Floor :iWashington,\nDC 20590\nDear Mr. Kelley,\"\nMatrix PDM requests a PHMSA ruling on the following questions we have pertaining to ASME\nPressureVessel-s·and HeatExclilangers, specifically.compliance t0 NFPA 59A (2001) and\nPHMSA FAQ D5 &,D6 when,constrwcting this equipment for an LNG Facility:\n-\n,\n,. 1) Regarding section 3.4.2 of NFPA 59A (2001) wherein the words \"pressure vessels\" are\nused, and section 3.4.3 of NFPA 59A (2001) wherein the words \"all heat exchangers\"\nare used, does PHMSA interpret these words to mean literally all pressure vessels and\nall heat exchangers within the boundary limits of any LNG Facility (under PHMSA\n_Jurisdicjion), regardless of pressure vessel or heat exchanger service (NG, Air, N2, etc.)\n- and regardless pf,the state.of the media contained (gas or liquid)? .\n1\n•\na. As an example, would this also include vessels and heat exchangers purposed\nV·-·, as either compressed air receivers, compressed instrument air dryer tower\nvessels (such as for packaged heatless desiccant instrument air dryer skids),\n. water propylene-glycol expansion tanks, water propylene-glycol air-cooled heat\nex,ch ngers, gaseous nitrogen storage vessels, or other similar vessels meant for\n100 Beecham Dr., Suite 200 I Pitts urgh, PA 15205 I P 412 471 5900 I matrixpdm.com\n\n<<<PAGE 7>>>\n\nMov to a higher standard\nMATR'l'l( P'D1M\nENGINEERING\nMr. Shane Kelley Page2 October 23, 2024\npurposes of utility, or for inert or non-toxic/ non-hazardous fluid service, and not\ncontaining hydrocarbons nor hazardous fluids in any form? (Hazardous Fluids as\ndefined in 49 CFR Part 193)\nb. Or do these requirements apply only to vessels and exchangers in hydrocarbon\nservice or hazardous fluid service? (Hazardous Fluids as defined in 49 CFR Part\n193)\n2) Does PHMSA FAQ DS & D6 and the requirements outlined therein for demonstrating\nsafety equivalency required by section 1.2 of NFPA 59A (2001) apply to literally all\npressure vessels and heat exchangers within the boundary limits of an LNG Facility,\nregardless of pressure vessel or heat exchanger service?\na. Or are these requirements limited to vessels and heat exchangers in either\nhydrocarbon service or hazardous fluid service as per the description given in\nquestion (1b) above?\n3) Does PHMSA fully adopt ASME BPVC Section VIII Division 1 paragraph U-1 Scope as it\npertains to which pressure vessels and heat exchangers must be designed, constructed,\ntested, inspected and stampe_d according to the rules of this Division versus those that\nare not considered to be within the scope of this Division?\na. If for example we have a vessel that qualifies as exempt per paragraph U-1, does\nthis mean that NFPA 59A (2001) section 1.2 and therefore PHMSA FAQ DS &\nD6 do not apply?\nAs standard practice we err on the side of a conservative interpretation of these rules but would\nnevertheless like to know if we're over-applying FAQ DS and D6 and the requirement for\ndemonstrating safety equivalency. We appreciate your assistance and forthcoming ruling on\nthese matters.\nBest regards,\nHanyPaiker@matrl\nHarry C. Parker, PE\nMechanical Supervisor\nCC: Chad R. Green, PE, Mechanical Chief (Matrix PDM)","truncated":false,"body_characters":17460}