{"operation":"document","citation":"17-0065","title":"Truck Trailer Manufacturing Association — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2018-07-23","effective_on":null,"summary":"17-0065 response to Truck Trailer Manufacturing Association concerning 178.345, 178.347, 180.407.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-17-0065.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-17-0065.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-17-0065","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/standards-rulemaking/hazmat/interpretations/58541/170065.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nPipeline and Hazardous\nMaterials Safety\nJUN 15 2018\nAdministration\nMr. John Freiler\nEngineering Manager\nTruck Trailer Manufacturing Association\n7001 Heritage Village Plaza, Suite 220\nGainesville, VA 20155\nReference No. 17-0065\nDear Mr. Freiler:\nThis letter is in response to your July 6, 2017, letter requesting clarification of the Hazardous\nMaterials Regulations (HMR; 49 CFR Parts 171-180) applicable to the installation of\nU.S. Department of Transportation (DOT) 400-series cargo tank vents on Motor Carrier (MC)\n300-series cargo tank motor vehicles (CIMV). Specifically, you include in your letter two\nscenarios and enclose guidance documents and a technical bulletin from your organization; one\ndriver/vehicle examination report; and a clarification letter on this topic issued by the Research\nand Special Programs Administration, the predecessor agency of the Pipeline and Hazardous\nMaterials Safety Administration (PHMSA).\nWe have paraphrased and answered your questions as follows:\nScenario 1:\nAn MC 307 CTMV fitted with a 30-pounds per square inch gauge (psig) pressure relief device\n(PRD) has a set discharge pressure of 30 psig (or maximum allowable working pressure\n(MAWP)) to 33 psig (110% of MAWP); see superseded $§ 178.342-4(c) and\n180.407()(1)(ii)(A). However, per the requirements in § 180.4070)(1)(ii)(B), a vent upgraded to\nconform to DOT 407 specifications on a 30 psig MAWP CTMV would be required to open\nbetween 36 psig (120% of MAWP) to 39.6 psig (132% of MAWP); see §§ 178.347-4(c) and\n178.345-10(d)(1).\n01.\nBased on Scenario 1, when upgrading an MC 307 CTMV PRD to a DOT 407 CTMV\nPRD, is the correct set-to-open pressure 120-132% of MAWP?\nA1.\nAn MC 307 PRD modified to conform to DOT 407 specifications on a 30 psig MAWP\nCTMV would be required to open between 36 psig (120% of MAWP) and 39.6 psig\n(132% of MAWP), as prescribed in §§ 180.407()(1)(ii)(B), 178-347-4(c), and 178.345-\n10(d)(1).\n\n<<<PAGE 2>>>\n\nScenario 2:\nAn MC 307 CTMV with a 30 psig MAWP originally had a PRD flow rated at 130% or 39 psig.\nThe original MC 307 design specification limited the flow to 130% per superseded § 178.342-\n4(0). In this case, the upgraded PRD would flow at 150% per the test pressure requirements\nprescribed in § 178.347-5; it would negate the requirement in paragraph (b) of superseded\n§ 178.342-4 and conform to the PRD requirements stated in § 178.345-10.\nQ2. Based on Scenario 2, when upgrading an MC 307 CTMV PRD to a DOT 407 CTMV\nPRD, is the correct flow pressure equal to the CTMV's test pressure?\nA2.\nAs prescribed in § 178.345-10(e), a DOT 400-series CTMV's flow rating is determined\nat a pressure not exceeding the CTMV's test pressure. Per § 178.347-5(b), the test\npressure of a DOT 407 CTMV must be the greater of 40 psig or 1.5 times (150%) its\nMAWP. Thus, the flow pressure for Scenario 2 must be no more than 45 psig, provided\nthe minimum venting capacity is met.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nI. Alexs Taste\nT. Glenn Foster\nChief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division\n\n<<<PAGE 3>>>\n\nstevens\n$180.405 (c)(2)(Ur)\naro\no lank\nTTMA\n7006.\nTRUCK TRAILER Assulacturers\nlank Conterence\nTTMAnet.org\nSince 1941\n7001 Heritage Village Plaza • Suite 220 • Gainesville, VA 20155 • 703-549-3010\nJeffrey M. Sims • President\nJuly 6, 2017\nU.S.DOT\nPHMSA-Office of Hazardous Materials Standards\nAttn: PHH-10\nEast Building\nWashington, DC 20590\n1200 New Jersey Ave, SE\nPhmsa.hm-infocenter@dot.gov\nSubject: Request for Interpretation - Venting Upgrades\nDear Sirs,\nWe are requesting formal interpretation of the provisions to upgrade venting as provided for under sections\n180.405(c)(2)(iv) and 173.33(d)(3) of title 49 CFR especially in light of a recent citation issued to Harnett Trucking\n(copy attached).\nIn that case, a specification MC-307 cargo tank with upgraded vents meeting the DOT 407 requirements was cited for\nnot meeting 178.343-4 and 180.405(c). The violation claims that the tank failed the inspection due to the inclusion of\na DOT 407 vent on an MC-307 cargo tank. This specific tank was manufactured with MC-307 specification required\nreclosing and fusible vents, and was upgraded post construction. However, many tanks built during the early '90s\nwere constructed as MC-307 or 312 cargo tanks with vents upgraded to DOT 407 or 412 vents similar to this tank as\nprovided for in the HMR:\n180.405(c)(2) A cargo tank of a specification listed in paragraph (c)(1) of this section may have its pressure relief devices\nand outlets modified as follows:\n(iv) A Specification MC 307 cargo tank, to conform with a Specification DOT 407 cargo tank (See $$178.347-4\nand 178.345-11 of this subchapter).\nAnd\n173.33(d)(3) A cargo tank motor vehicle made to a specification listed in column 1 may have pressure relief devices or\noutlets may be modified to meet the applicable requirement for the specification listed in column 2 without changing\noutlets conforming to the applicable specification to which the tank was constructed, or the pressure relief devices or\nthe markings on the tank specification plate. The venting capacity requirements of the original DOT cargo tank\nspecification must be met whenever a pressure relief valve is modified.\nColumn 1\nColumn 2\nMC 307\nDOT 407.\n\n<<<PAGE 4>>>\n\nIt has been standard industry practice to apply upgraded venting when the opportunity presents, as the new venting was\nseen to be safer as it banned non-reclosing devices such as fusible caps or rupture discs except when under a reclosing\npressure relief device, and provided for greater product retention in an overturn due to the higher set pressures. When\nthe caution in 173.33(d)(3), \"The venting capacity requirements of the original DOT cargo tank specification must be\nmet whenever a pressure relief valve is modified\" is brought up, stakeholders relied on the 1996 letter of interpretation\nsigned by Hattie Mitchell stating that the caution is not intended to prevent upgrades that are flow rated according to\nthe DOT 400 specification, i.e., vents that achieve their flow rate only at the tank test pressure rather than the 130% of\nMAWP. The caution is there to require that flow rates be checked carefully against the requirements anytime the\npressure relief devices are modified.\nThat letter referenced 180.405(h)(3) which says:\nAs provided in paragraph (c)(2) of this section, the owner of a cargo tank may elect to modify reclosing pressure relief\n§178.345-10 of this subchapter must provide the minimum venting capacity required by the original specification to\ndevices to more recent cargo tank specifications. However, replacement devices constructed to the requirements of\nwhich the cargo tank was designed and constructed.\nGiven the similarity in language between the caveat here and the language in 173.33(d)(3) stakeholders have\nunderstood that the flow rates of vents that have been upgraded is to be determined as required for the new\nspecification: i.e. at tank test pressure per 178.345-10.-\nAdditionally, PHMSA recently added 180.407(), Pressure Vent Bench Test, to make the opening pressures for vents\nclearer. For an MC-307 tank with vents upgraded to DOT 407 the code requires that the vents be set \"according to the\npressures set forth for a DOT 407 cargo tank in $178.347-4 of this subchapter.\" See 180.4070)(1)(ii)(B). §178.347-4\nrequires that pressure vents be set in accordance with §178.345-10(d), which states:\n(d) Settings of pressure relief system. The set pressure of the pressure relief system is the pressure at which it starts to\nopen, allowing discharge.\n(1) Primary pressure relief system. The set pressure of each primary relief valve must be no less than 120 percent of the\nand remain closed at lower pressures.\nMAWP, and no more than 132 percent of the MAWP. The valve must reclose at not less than 108 percent of the MAWP\nIt's clear that when a MC-307 cargo tank has its pressure relief devices upgraded, the HMR requires that they will\nconform in all ways to the upgraded specification. That is, it is set and flow rated according to the DOT 407\nspecifications at the cargo tanks test pressure and the original specification is consulted only to determine the required\nflow rate for the cargo tanks surface area at to be in compliance.\n\" We believe that this citation, if allowed to stand, will create a safety risk for these tanks with\nupgraded venting. The upgraded vents are better performing and the prohibition against non-\nreclosing vents and higher set pressures means that retention of the hazardous commodity being\ntransported is maximized. The consequences of allowing this citation to stand is to essentially outlaw\nupgrades: carriers will change back to MC-307 vents and fusible caps and lose the safety gains with\nthe newer DOT 407 venting. Additionally, MC-307 cargo tanks with vent upgraded to DOT 407\nspecifications venting has been the industry norm for about 25 years without a reported incident\ncaused by the use of these upgraded vents; a change now would be a tremendous waste of resources,\ncausing confusion and the possibility of worker injury or mistaken vents being placed during the\nunnecessary and unwarranted change.\n\n<<<PAGE 5>>>\n\nBackground on the addition of the provision in 173.33(d)(3) requiring \"The venting capacity\nrequirements of the original DOT cargo tank specification must be met whenever a pressure relief\nvalve is modified\":\nthose meetings, there was much concern expressed by vent makers in regard to the so-called \"Smart Vent\" or \"Dual\nThis provision was added to the code in response to comments made at public meetings that I attended. At\nFunction\" requirements ‹ the reduced leakage during surge requirements laid out in (b)(3) (b)(3)}. Betts\nIndustries, a leading Manufacturer of vents for MC-306 cargo tanks had developed a style of vent for the DOT 406\nrequirements that would leak less than one gallon during surge (the proposed requirement at that time), but those vents\nhad a reduced capacity at the set and flow rate pressures for a DOT 406 cargo tank when compared to the vents\ncurrently in service on MC-306 tanks. It was felt that a potential safety hazard existed wherein a MC-306 cargo tank\noperator could replace his existing vents one for one with the new smart vents, not realizing that their capacity as\nmeasured at the DOT 406 pressures would be lower in terms of SCH than that cargo tank originally required. This\nlead to the following entry in the Federal Register Vol. 59, No. 212, Thursday, November 3, 1994, pg. 55163 & 55169:\nPage: 55163:\nSection 173.33\nConsistent with the changes made in § 180.405(h) in this final rule, a new sentence is added to\nparagraph (d) stating that the venting requirements of the original DOT cargo tank specification must be met\nwhenever a pressure relief valve is modified to a more recent specification. See preamble discussion for §\n180.405(h).\nPage: 55169:\nSection 180.405\nvalve must be capable of re-seating to a leak-tight condition after a pressure surge. Section 180.405(c)\nParagraph (h) specifies that replacement for any pressure replacement for any reclosing pressure relief\nauthorizes modifying the reclosing pressure relief valves of an MC 306 cargo tank by installing the dual\nfunction pressure relief valves which are required for DOT406 cargo tank motor vehicles. Commentators\npointed out that this replacement could result in an MC 306 cargo tank having lower emergency venting\ncapacity than its specification requires: because it is difficult to produce a valve that achieves the\ncomparatively high flow rates of the MC 306 units, withstands the pressure surges specified in the DOT 406\nspecification, and recloses with minimal loss of lading. A reduced flow capacity is less likely to be\nencountered in fitting and MC 307 with a DOT 407 valve replacement, and in fitting an MC 312 with a DOT\n412 valve replacement, because of the larger pressure differentials which are commonly used in these cargo\nspecification must be met whenever a pressure relief valve is replaced. ..\ntanks. Regardless of the equipment installed, the venting requirements specified in the particular cargo tank\n\n<<<PAGE 6>>>\n\nQ1. When upgrading an MC-307 cargo tank's pressure relief device to a DOT 407 pressure relief device, is the correct\nset to open pressure 120% to 132% of MAWP?\nFor example, an MC-307 30psig pressure relief device has an allowable set to discharge pressure of 30psig (or\nMAWP) to 33psig (110% of MAWP); see §178.342-4 (c) and §180.407()(1)(ii)(A). However, per the requirements in\n8180.4070(1)(i1)(B), a vent upgraded to conform with DOT 407 specs on a 30psi MA WP cargo tank would be\nrequired to open between 36psig (120% of MAWP) to 39.6psig (132% of MAWP); see §§178.347-4(c) & 178.345-\n10(d)(1).\nQ2. When upgrading an MC-307 cargo tank's pressure relief device to a DOT 407 pressure relief device, is the correct\nFLOW PRESSURE equal to the tank's test pressure?\nFor example, an MC-307 tank with a 30psig MAWP normally has a pressure relief device flow rated at 130% or\n39psig. The original design regulation specification limited the flow to 130% per §178.342-4 (b). So, in this case, the\nupgraded pressure relief vent would flow at 150% per the test pressure requirements stated in §178.347-5. It would\nnegate the requirement in section (b) of §178.342-4 and conform to pressure relief requirements stated in §178.345-10.\nWe understand that PHMSA and the industry share the position that safety is enhanced with upgraded vents. We hope\nwe can continue this cohesiveness and further hope that an expeditious clarification will prevent needless wasted\nefforts and the degradation to safety and risks to workers with needless vent replacements.\nIf you have any questions at all, please feel free to contact me.\nSincerely,\nJohn Freiler\nJohn Freiler\nEngineering Manager\ncc\nGlenn Foster, Chief, Regulatory Review and Reinvention\nStan Staniszewski\nEncl.\nBackground on 173.33(d)(3)\n1996 Hattie Mitchell Letter\nHarnett Trucking citation and supporting photos.\nTTMA Position paper on Venting Upgrades\nTB 126 Bench Testing Pressure Relief Devices\n\n<<<PAGE 7>>>\n\ninterp\nINTERPRETATION\nU.S. Department\nof Transportation\nWashington, D.C. 20590\n400 Seventh Streel. S.W.\nSpecial Programs\nResearch and\nAdministration\nRef. No. 96-1094\nJUN I O 1996\nMr. John Freiler\nSenior Pröject Engineer\nGirard Equipment, Inc.\nPO Box 302-B\nRahway, NJ 07065\nDear Mr. Freiler:\nThis is in response to your letter requesting clarification of\nthe pressure relief requirements specified in 49 CFR 173.33 (d) .\nSpecifically, you asked if $ '173.33 (d) (3) prohibits upgrading\nvents on MC 307 and MC 312 cargo tanks to DOT 407 and DOT 412\nvents that are flow rated in accordance with § 178.345-10. I\napologize for the delay in responding and regret any\ninconvenience it may have caused.\nThe answer is no. Section 173.33 (d) (3) provides that pressure\nvehicle listed in column 1 may be modified to meet the applicable\nrelief devices. or outlets on a specification cargo tank motor\nrequirements for the specification listed in column 2. However,\nreplacement devices constructed to the requirements of § 178.345-\noriginal specification to which the cargo tank was designed and\n10 must provide the minimum venting capacity required by the\nconstructed. See § 180: 405 (h) (3).\nI trust this satisfies your inquiry.\nsincerely,\nHothe z. michell\nHattie I. Mitchell, Chief\nOffice of Hazardous Materials Standards\nExemptions and Regulations Termination\n173.33(0)\n961094\n\n<<<PAGE 8>>>\n\nJun 071702:48p\np. 1\nDRIVER/VEHICLE EXAMINATION REPORT\nAspen 3.0.0.17\nIllinois Division\nFederal Motor Carrier Safety Administration\nReport Number: US1459000551\n3250 Executive Park Drive\nInspection Date: 05/16/2017\nSpringfield, IL 62703\nStart: 02:24 PM CT End: 3:26:14 PM CT\nFax 217-492-4986\nInspection Level: |- Full\nHM Inspection Type: Bulk\nL T HARNETT TRUCKING INC\n7431 STATE ROUTE 7\nDriver: STILTNER, JIMMY R\nKINSMAN, OH 44428\nLicense#: RU636599\nState: OH\nMC/MX#: 170992\nUSDOT#: 00239562\nPhone#: (330)876-2701\nDate of Birth: 03/27/1944\nState#:\nFax#:\nCoDriver:\nLicense#:\nLocation: MARSHALL SCALES\nDate of Birth:\nState:\nCounty: CLARK, IL\nHighway: 170 WB\nMilePost: 151\nrigin: COLUMBUS, OF\nShipper: OPC POLYMERS\nDestination IMPERIAL, MC\nBill of Lading: 66877\nCargo: LIQUIDS/GASES IN TANKS\nVEHICLE IDENTIFICATION\n1 Unit Type Make Year State\n1\nTT INTL\n2006 OH\nPlate #\nEquipment ID\nVIN\n2 ST POLA 1994 OH\nTPL9175\nPVR7200\n4\nGWR CVSA# CVSA Issued # OOS Sticker\n2865\n2HSCNAPR66C301602\n52,000\n1PMS34227R1012865\n58,000\nBRAKE ADJUSTMENTS\nAxie #\n11/8\n1\n2\nChamber\nLeft\nRight\nL-20*\n1\n1 1/8\n3\n3/8\n3/4\n4\nL-30\nL-30\n3/4\n11/4\n5/8\n1\nC-30\nC-30\n1 1/4\nVIOLATIONS\n393.45PC\nVio Code\n393.45\nSection\nUnit OoS\nCitation # Verify Crash Violations Discovered\nBrake Tubing and Hose Adequacy - Connections to Power\n393.45B2PC\n393.45(b)(2)\n2\nN\nN\nN\nBrake Hose or Tubing Chafing and/or Kinking - Connection to\nUnit: Axle 2 Left Emergency hose cut core exposed\n178.342-4\n180.405(c)\n2\nN\nN\nN\nMC307 venting: MC307 (30psig MAWP) equipped with MC407\nPower Unit: Servie side chafing rubbing against cat walk\n• vent with a set pressure of 36psig (MAWP).\nHazMat: 3 Flammable\nSpecial Checks: No Data for Special Checks.\nPlacard: Yes\nCargo Tank: 407\nPursuant to authority contained in Title 49, Code of Federal Regulations, Section 396.9(c), I hereby declare vehides with detects followed by an \"Y' in the \"Out of Service\" column in the\nservice defects have been repaired and the vehicles have been restored to safe operating condition.\nviolations discovered section of this repart OUT OF SERVICE. No person shall remove the out of service stickers applied to these vehicles, or operate such vehicles until the out of\nSignature Of Repairer X:\nFacility ELS\nDate S16-/8\nпоитонских Fon Sult\nDate: 66-7-17\nPage 1 of 1\nStitue\n00239562 IL US1459000551\n\n<<<PAGE 9>>>\n\nHarnett Trucking\n• DOT407 violation of MC307 upgrade\n3\n\n<<<PAGE 10>>>\n\nVEG EV: POLAR TANK TRAILER INC.\nMONTH AND YEAR IN WHICH FINAL\nGROSS VEHICLE WEIGHT RATING\nSTAGE MEG. IS COMPLETED:\nLBS\nGROSS AXLE WEIGHT PATING\nAXLE NO.\nGROSS WEIGHT RATING\nALL\n(FROM FRE OF VEHICLE\nCLAS\nWITH\nERIMS, AT.\nTIRES\n(FROM FRE OF VEHICLE\nFRIE\nFROM 2R\nBENEMIES\nTIRE\nGERMS. AL\nTHIRDERO ECONOMS TALLAN\nLERAL\nNOTOR VEHICLE SAFETY SIANDAS\nEATBOF MANUFACTURE SINOWN\nJEHICLE DOEN THIGATON NO ILLE\nASSIFICATION OF VI HIGLA\n\n<<<PAGE 11>>>\n\nMANUFACTURED BY\nPOLAR TANK TRAILR\nMFG. SERIAL\nR1-12865 MFG. LATE 77 68\nD.O.T. SPEC. MC COT\nORIGINAL TEST\n7795\nCERTIFICATION DATE 7/2\nDESIGN PRESSURE\n30\nS.J.G.\nTEST PRESSURE\nSIG\nHEAD MATL 212MINTEG\nSHELL MAT'L\nWELD MAT'L\n8116\nLINING MAPL\nNOMINAL COMP'T CAP (FRONT TO REAR)\nU.S. SALS\nMAX. PROD. W\n58000\nLBS GAL\nMAX. PROD LOA\nLBS. MAX. TEMP\nLOADING EMI\nCHEN\nUNLOALING LIT\nO MONE\nSP2865\nF-NNIN\n\n<<<PAGE 12>>>\n\nFrom:614 630 8886\n05/16/2017 17:08\n#926 P.006/011\n#2865 Cl\nTREMCAR\nTREMCAR U.S.A. INC.\n135 12t1 Street NE. • Strasburg. Ono 14bbo\nTANK TRAILER SPICIALISTS\nPrune: 330-8/8-1708 • Fax 320-878-5074 • Iol Free: 088-TREMCAR\nEXTERNAL VISUAL INSPECTON REPORT\nDOT NUMBER: CT-10556\nin accordance with 49 CFR pat 180 Para. 180.470 (d))\nR Stamp Repalr Required\n฿ R -6563\nYes_ No\nCustomer L..T. MARNETT\nMC/DOT No.....\n307\nManufacture._\nDate...\n3-14 binE\nSerialNo. 1PMS 34221R101286\nUnit No._.....\n2865\nYear of MFR.\n1993\nOriginal shell thickness....\nNA\nOriginal head thickness\nMAWP/Design Pressure.\n_30\nMin. Shell Thickness\n→121\nMin. Head Thickness\n.112\nN/A\nCargo Tank Is Jacketed\nCap. Comp. 1. 7000\ninsulated\nN/A\nRyes\n\\ Yes\nNo\nSpecial Service\nLast Service Date.\n_No\n_NO\nLast Service Product\n2-16\n-... Last Service Miles ..\n\"Cargo tank used to haul product corrosive to tank\n(Required every two years for tank in corrosive service)\nUpper Coupler Assembly Remored\n-X. res\nX res\n...No\n_No\nINSPECTION STEPS\nAcceptable\nNon-\nSee\nAcceptable\nCorrective\n1.Shell and heads: condition of wells-dents-\nAction\n2.Upper coupler assembly; condition of plate-\nGouges-corrosion or abrasion…........\nValve installations-valve operator installation-\n3.Bolted attachments: piping brackets and supports\nUndercarriage attachments\nDust cap retainers-all tank-to-frame and/or\n4. All major appurtenances and structural attachments\nOn the cargo tank, including suspension system\nMembers, outriggers and boister..............\nAttachments, connecting structures, framels, cross\" t\n5. Piping and all valves and adapters: attachments-\nLeakage-handles and levers-cables or alr lines-\nShear sections duit caps all gaskets or ortings: X\nlubrication poin........\n(Normal, remote, and thermal)- function check-\n6. Internal valve operation: three means or closure\n\n<<<PAGE 13>>>\n\nFrom:614\n539 8886\n06/16/2017 17:10\n#925 P.010/011\n*:\n-\nTREMCAR\nTREMCAR U.S.A. INC.\n136 121h Streel Ni - Straspurg, Ohio i 1680\nTANK THALEP SPErIALISTS\nPhone 330-878-7708 • fax: 330-878 3074 • Toll Freo' 886 TREMCAR\nDOT NUMBER: CT-10556\n_Hydrostatic or pneumatic, EPA Mettrod 27- when applied\nLEAK TEST REPORT\nTest Liquid MR oveR Mee\nin accordance with 49 CFR Part 180 Para. 180.407 [h)\nStamp Required... Yes _No\nMC/00 .......\nCustomer\nLT. MARNETT\n#R-6563\n307\nDate.\n3-14-17\nserial No. J PMS 34227R1012865\nUnit No..\n2865\nYear of MFR.\nManufacture....\nPOLAR\n1993\nOriginal shell thickness\nMAWP/Design Pressure\n30\nMaterial\nMin. shel Thickness 316\n121\nMin. Head Thickness\nOriginal head thickness.\n112\nNA\nInsulated\n_Yes._ No\nComp 1\nараст\nTest pressure\n24.0\nStart Time\nEnd Time\nComp. 3\nComp. 7\n7:56\n7:41\nComp. 4\nComp. 5.\nVents Removed & Tested\nSet To Discharge\nComp.\n1\nN\n2\nOpen Pressure\n368\n4\n5\nVent Type\nReseal Pressure\n36,0\n33,0\nDisposition\nGIRARD\n30 * 407\nRemarks\nRemoved\nReplaced\nReinstalled\nafter completing bench test requirements Including normal yents if ok.\nThe following must be completed for each compartment. Red fisg all vents removed or rendered Inoperative. Reinstall vents\nAcceptable\n(See Remarks)\nNonacceptable\nInstall test fitting into manhole assembly\nManhole, open internal valve (if appropriate)\nCleanout or any other top opening. Close\nAnd gradually pressurize to 80% of MAWP.\n\n<<<PAGE 14>>>\n\nTTMA\nRUCK TRAILER manufacturer\nTank Conference\nssociatio\nTTMAnet.org\nSince 1941\nJeffrey M. Sims • President\n7001 Heritage Village Plaza • Suite 220 • Gainesville, VA 20155 • 703-549-3010\nTTMA Position on MC 307 to DOT 407 Venting Upgrades\nUpdated December 17, 2015.\nABSTRACT\nTTMA summarizes the history and rationale behind the venting changes made when DOT authorized\nnew 400 series cargo tanks. The HMR allowed owners of older cargo tanks to upgrade their venting\nsystems to the new code, and the industry embraced this. However, a small minority of users have\nsome confusion, both about what the HMR requirements actually specify and what is best practice. This\npaper describes the requirements as laid out in the HMR and in official code interpretations from DOT.\nBACKGROUND\nThe Truck Trailer Manufacturers Association (TTMA) is an international trade association formed in 1941\nrepresenting approximately 90% of the trailers manufactured in the United States. TTMA works closely\nwith both regulators and end users.\nIn September of 1990, Docket HM-183 was advanced and the Code of Federal Regulations was modified\nfor construction of cargo tanks. Prior to 1990, DOT had spent a number of years investigating the\ndesign, construction and safety of cargo tanks hauling hazardous materials. The old Motor Carrier (MC\n306, 307, 312) codes would not be used for cargo tank construction after September 1, 1995. All cargo\ntanks would be constructed to the new DOT 407 code, three notable differences were:\n• Removal of fusible and/or frangible disc from the pressure relief system.\n• Set to discharge changed from (MAWP to +10%) to (120% to 132% of MAWP).\n• Flow rate calculation threshold shifted from 130% of MAWP to 150% of MAWP.\nIn reviewing actual performance of cargo tanks, DOT concluded the safety record of tanks could be\nimproved. For venting, the MC codes were designed primarily around preventing catastrophic failure of\nthe tank. However many accidents didn't involve catastrophic scenarios, but were less severe (more\ncommon) sorts of events; for example, a tank rolling-over on a highway exit ramp. In these events, the\ndesign of the MC code venting allowed release of product - when it could possibly have been prevented.\nChanges were put forward to continue to provide catastrophic levels of protection, while also increasing\ncargo retention in less severe incidents.\nFusible and frangible devices as stand-alone pressure relief devices were removed from cargo tanks\n(about) 25 years ago. This was done to provide improved containment of the hazardous materials.\nIndustry embraced this change, and it has been a great improvement to the cargo tank design.\nThe set-to-discharge pressure range was increased a slight amount from MC 307 to DOT 407. This\nincrease in pressure range does not have any negative affect on the structural integrity of the cargo\ntank, since both designs are subject to test pressures of at least 150% of MAWP. The higher set-to-\n\n<<<PAGE 15>>>\n\ndischarge pressure allows for variations and hysteresis within acceptable limits of use. This change\nallows the pressure relief device to reseat and seal before dropping below the MAWP.\nBoth of these changes serve to contain the product in the cargo tank in the event of a rollover far better\nthan the earlier designs. In a rollover, a fusible or frangible device that had opened could allow the\nentire cargo to escape the tank. The increased set-to-discharge pressure served to protect the tank\nfrom discharging when the weight of the cargo (head) was added to any internal pressure (when the\ntank was inverted).\nCHALLENGE\nThe HMR allow for pressure relief devices to upgraded to the newest specification in §§180.405(c)(2)\nand 173.33(d)(3). Thousands of MC 307 cargo tanks were produced between 1990 and 1995 with DOT\n407 compliant vents. Moreover, many owners of older cargo tanks from the MC 307 years desired an\nupgrade to newer pressure vents. WHY? Industry didn't want to maintain the older style of cargo tanks\nwith fusible devices that needed to be constantly replaced. They wanted to be environment friendly\nwith robust re-closing pressure relief devices. It made sense then and still does today. They wanted\nhigher flow rates from the DOT 407 pressure relief devices.\nOn the other hand, some groups have misconstrued or misunderstood the wording and intent of the\nchanges to the Code of Federal Regulations. Their misguided interpretations would allow fusible devices\nback on MC 307 cargo tanks with DOT 407 compliant venting, along with greatly reduced pressure relief\ndevices. Seemingly, they don't understand the applicable engineering principles.\nWill the design of the MC 307 cargo tank be compromised in any form or fashion if the set to discharge\npressure is increased by 10%? Should the flow rates be calculated at 130% or 150%? Both of these\nquestions are technical in nature and are answered best by design certifying engineers familiar with\ncargo tank design and construction.\nUNDERSTANDING THE DESIGN\nFusible and/or frangible device background:\nFusible vents have been used on cargo tanks since the 1950's. Typically, a fusible device consists of a\nthreaded connection holding a fusible element and a disc. The fusible device is designed to yield at an\napproximate temperature of 250°F. The fusible device communicates with the vapor space of the tank.\nIn a fire emergency, the fusible element would melt and provide an outlet for vapor pressure to escape\nfrom the tank vessel. In a catastrophic fire, the boiling liquid could cause a rupture resulting in damage,\npossible injury and release of the lading. The fusible device creates an inexpensive form of venting the\ncargo tank's pressure, potentially suppressing the rupture.\nDuring the 40 year period from 1950 to 1990 many improvements were made to manufacturing fusible\nvents. With all of the improvements, the fact remains that this type of relief device is non-reclosing.\nOnce opened, it will stay open until manually replaced. Tank trucks are subject to high shock and\nvibration loads on a regular basis. Fusible vents are not able to withstand the high vibration load over\nan extended period of time. When subject to these vibration loads, the fusible vent may open at an\n2\n\n<<<PAGE 16>>>\n\ninopportune time. The surrounding environment would then unnecessarily be exposed to toxic, harmful\nvapors. Heat systems are used on some tank trucks that transport thick viscosity ladings. These heating\nsystems sometimes operate very near to the temperature range that a fusible device is required to yield.\nThe high heat eventually degrades the fusible vent and causes it to open. Another form of adverse heat\nto the fusible vent is steam from tank cleaning operations.\nGuidance from DOT:\nIn the 1980's, when DOT was contemplating re-writing cargo tank regulations, they held several public\nmeetings that TTMA members attended. Officials from DOT clearly and succinctly stated their thoughts\nand intentions regarding fusible devices in the passage, below.\nIn the Federal Register (Volume 50, No.180, p.37776, Tuesday September 17, 1985) DOT stated:\n5. We believe that the risk from hazardous material transportation is substantially reduced\nwhen packaging is designed to retain the lading in non-catastrophic accidents and to minimize\nthe quantity of lading released when release is inevitable. However in a cargo tank accident,\nparticularly an overturn followed by a fire, the functioning of a frangible disc or a fusible\nelement would result in the release of a substantial quantity of lading. A reclosing pressure\nrelief device on the other hand would minimize the quantity of lading released. Further we\nbelieve that a frangible disc and fusible elements particularly in low pressure applications are\nmuch more likely to fail as a result of impact and liquid surge than reclosing pressure relief\ndevices. Accordingly, for all cargo tanks constructed after the effective date of the final rule,\nwe are proposing that all pressure relief devices be re-closing except a frangible disc may be\nused in series with a reclosing pressure relief device.\nTTMA believes that DOT had a thorough understanding of fusible/frangible devices and focused a great\ndeal of their attention to eliminating the use of non-reclosing devices. This greatly enhances tank safety\nand protects public interest. How, one might ask? First, when a rollover occurs with an opened fusible\ndevice, lading is almost always released; conversely, reclosing pressure relief devices release lading only\nwhen there is pressure on the tank. Secondly, the release of non-accident vapors to the atmosphere is\nprevalent when using fusible devices that have failed due to impact and/or liquid surge. This inadvertent\nrelease of vapors is greatly reduced or eliminated with the use of reclosing pressure relief devices.\nMC 307 Venting systems:\n49 CFR 178.342-4, (a) through (d) specifies safety relief vents on MC 307 Cargo Tanks. The device will\nconsist of pressure-actuated spring loaded device, otherwise known as a reclosing safety relief device.\nWhen necessary to meet the venting capacity of Table Ill, one or two fusible and/or frangible devices\nwould be added to the total venting system. The spring loaded safety relief device in this system makes\nup a subpart of the total capacity of the pressure relief system. The fusible or frangible device(s) are\nused to augment this system.\nDOT 407 venting systems:\n3\n\n<<<PAGE 17>>>\n\n49 CFR 178.345-10 (a) through (h) specifies the requirements for DOT 406, 407 and 412 series pressure\nrelief system. Specifically, 178.345-10 (b) (1) requires that each primary pressure relief system consist of\none or more reclosing pressure relief valves. Furthermore, non-reclosing (e.g., fusible disc) pressure\nrelief devices are not authorized in any cargo tank. The venting capacities from Table I will require one\nor more reclosing pressure relief devices.\nNote: reclosing pressure relief manufacturers were able to meet the higher flow requirements of\n178.345-10 by changing the design pressure of the relief device, increasing the flow rates by up to 10\ntimes.\nThe clear intent by the DOT was to remove any fusible and/or frangible disc from trailers hauling\nhazardous cargo, due to safety concerns for the general population.\nUpgrading MC 307 to DOT 407:\nThere are three different sections of code that address upgrading MC 307 cargo tanks to DOT 407 cargo\ntanks. §173.33(d) (3) specifies that the pressure relief devices may be modified from MC 307 to DOT\n407. Again, $180.405 (c) (2) states that an MC 307 cargo tank may have its pressure relief devices\nmodified to conform to the DOT 407 specification. Lastly, §180.405(h) (3) says the owner of a cargo tank\nmay elect to modify reclosing pressure relief devices to more recent cargo tank specifications, however\nit must provide minimum venting capacity required by the original specification. The Federal\nGovernment clearly wanted cargo tank owners to willfully consider upgrading MC 307 pressure venting\nsystems to DOT 407 code. None of the three cited codes suggests leaving fusible vents in place, nor\ndoes it mention having to update the set to discharge pressure from 120% of MAWP to MAWP, or\ncalculating the flow rates at 130% of MAWP. Instead, they clearly state how to upgrade the pressure\nsystem to the new code requirements.\nWhile some have misinterpreted the caution to ensure that upgraded vents have sufficient capacity to\nprevent cargo tank rupture as meaning that the pressure vents must be rated at the original pressures,\nthis was settled when the DOT issued an interpretation dated June 10, 1996 and signed by Hattie L\nMitchell which said:\n-Specifically, you asked if §173.33(d)(3) prohibits upgrading vents on MC 307 and MC 312 cargo tanks\nto DOT 407 and DOT 412 vents that are flow rated in accordance with §178.345-10.\n000\nThe answer is no. ...\nHOW TO MEET THE REQUIREMENTS\nFusible devices shall not be employed on cargo tanks with DOT 400 series compliant venting, including\nMC 307 units. The results are evident! There is a much lower non-accident release record. Lading is not\nbeing poured out needlessly when trucks are involved in rollover accidents without explosions. Toxic\nvapors are not being released to our atmosphere.\nSet-to-discharge requirements of the DOT 400 series venting regulations are easily met. The increased\ntolerance range of 120% to 132% MAWP is easier to qualify during bench testing, the possibility of set-\n4\n\n<<<PAGE 18>>>\n\nto-discharge going under the MAWP has been eliminated, and reseat (or reseal) of the pressure relief\ndevice occurs before reaching MAWP. The change in set-to-discharge pressure does not have adverse\neffects on the structure or integrity of the shell design for the cargo tank.\nAs a general physics statement, mass flow proportionally increases with pressure. During a catastrophic\nevent, a rapid temperature rise will consequently increase flow rates. The older, outdated pressure\nrequirement of 130% to MAWP for the mass flow calculation has been abandoned. All transportation\nindustries embrace the updated flow pressure requirement of 150%. This calculation is applied to trains,\nships, and other forms of transporting hazardous materials. TTMA fully embraces this shift and sees no\nreason to apply an outdated standard to cargo tanks.\nTTMA has noted an untarnished safety record for upgraded MC 307 cargo tanks using the modified DOT\n407 pressure relief systems over the past 25 years. This track record stands by itself. Thousands of\ncargo tanks have been built and continue to be in service using this system, working safely, as intended.\nABOUT THE USERS WHO HAVE MISINTERPRETED THE UPGRADE REQUIREMENTS\nTTMA is aware of some people advancing the idea that pressure relief devices, especially those on MC\n307 cargo tanks cannot be upgraded to DOT 407 vents set and flow rated according to the DOT 407\nrequirements. This small group of users continues to operate cargo tanks with the misunderstanding\nand misinterpretation that requires a fusible device and flow rate calculations at 130% of MAWP. They\nfeel it is the only way to be in complete compliance with the code. However, by applying pressure relief\ndevices that are set and flow rated according to the original specification, they have simply forgone\nupgrading. They are operating their cargo tanks with pressure relief meeting the requirements when\nthe cargo tank was built as provided for in 173.33(h)(2). They do not necessarily gain the benefits of\nhaving better lading retention and fully reclosing devices of the DOT-400 series requirements.\nTTMA does not recommend mixing devices: A DOT-407 venting system is not designed to be operated\nin conjunction with non-reclosing vents alongside it. DOT's intent was to eliminate non-reclosing\ndevices to maximize retention of hazardous materials, and allowing fusibles to continue to operate on\notherwise upgraded systems would be contrary to that mission. Further, this is most often done due to\noperator error: There is no need to provide a fusible vent alongside DOT 400 series reclosing device as\nthese are adequately sized to provide sufficient flow to protect the cargo tank from rupture.\nCONCLUSIONS\nThe clear intent by DOT is to have all fusible devices removed. Neither the integrity of the MC 307 cargo\ntank, nor the pressure relief system will be degraded - if the set to discharge pressure is increased from\nMAWP to 120%. It is a correct interpretation of the CFR - and also safe - to install DOT 407 pressure\nrelief devices on MC 307 cargo tanks. Lastly, a calculated flow rate of 150% of MAWP is a standard used\nthroughout transportation industries around the world.\n5\n\n<<<PAGE 19>>>\n\nTTMA TECHNICAL BULLETIN\nTRUCK TRAILER MANUFACTURERS ASSOCIATION\n8506 WELLINGTON RD. / SUITE 101\n(703)549-3010\nMANASSAS, VA 20109\nwww.ttmanet.org\nTB No. 126\nNovember 15, 2012\nTitle: Bench Testing Reclosing Pressure Relief Devices\nPrevious Editions:\nOriginally issued November 2012.\n1.0 Preface:\n1.1\nNo part of this document may be reproduced or transmitted in any form or by any means, electronic or\nmechanical, including photocopying, recording, or by any information storage or retrieval system without\nwritten permission from the Truck Trailer Manufacturers Association.\n1.2\nRecommended Practices and Technical Bulletins are furnished by the TTMA as a guide to general practices\nPractices and Technical Bulletins is not exhaustive of all general practices in the manufacture, use, and\nin the manufacture, use, and repair of truck trailers. However, the scope of the TTMA's Recommended\nrepair of truck trailers and there may exist such general practices which do not appear in either the\n1.3\nRecommended Practices and Technical Bulletins represent the state-of-the-art that existed at the time of its\nadvancements in practices that have occurred subsequent to the Recommended Practice's or Technical\npreparation. Users of Recommended Practices and Technical Bulletins should familiarize themselves with\n1.4\nPractices or Technical Bulletins may be used by manufacturers, users, or repairers of truck trailers nor the\nThe TTMA has not undertaken any evaluation of all the conceivable ways in which Recommended\nconsequences of such uses. Everyone who uses Recommended Practices or Technical Bulletins must first\nother equipment will not be jeopardized by their use of information contained within the Recommended\nsatisfy himself or herself that his or her safety, the safety of others, or the safety of the truck trailer and any\n1.5\nmeanings. Definitions for such terms or words may be found in TTMA RP No. 36 - Tạnk Trailer and Tank\nThe Recommended Practices and Technical Bulletins may contain terms or words with specializer\nContainer Nomenclature or TTMA RP No. 66 - Trailer Nomenclature.\n1.6\n1.7\nCod any no won formity public to ply cations is ner dead or tie non-conck ming pis ted being.\n1.8\nAny inclusion of R","truncated":true,"body_characters":51157}