{"operation":"document","citation":"10-0195","title":"National Oilwell Varco — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2011-06-29","effective_on":null,"summary":"10-0195 response to National Oilwell Varco concerning 178.273, 178.274.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-10-0195.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-10-0195.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-10-0195","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretations/2010/100195.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department ofTransportation Pipeline and Hazardous Materials Safety Administration\nHanke Wang, Ph.D., P.E.\nSenior Project Engineer National Oilwell Varco\n2800 N Frazier St.\nConroe, TX 77303\n1200 New Jersey Ave, SE\nWashington, D.C. 20590\nJW' ('\\ 9 2011\nReference No. 10-0195\nDear Dr. Wang:\nThis is in response to your e-mail requesting clarification of the Hazardous Materials\nRegulations (HMR; 49 CFR) applicable to UN portable tank design criteria. Specifically, you\nask for the definition of\"design margin of 1.5\" as it is used for determining the safety tactor\nin § 178.27 4( c )(2). You state that it is your understanding that a design margin of 1.5 could\nresult in a safety factor of 2.5 (1.5+1=2.5).\nSections 178.274( c)(2)(i) and (c)(2)(ii) state that the safety factor under each of the forces\nspecified in paragraph § 178.274(c)(1) must be:\n(i) For metals having a clearly defined yield point, a design margin of 1.5 in relation to\nthe guaranteed yield strength; or (ii) For metals with no clearly defined yield point, a\ndesign margin of 1.5 in relation to the guaranteed 0.2% proof strength and, for austenitic\nsteels, the 1 % proof strength.\nThe term \"design margin of 1.5\" is the safety factor to which the UN Specification portable\ntank must be designed by calculating the stresses resulting from acceleration loads applied to\nthe tank. The two terms are used interchangeably in the HMR (design margin § 178.274\n(c)(2)) and UN Model Regulations (Volume 1 Section 6.7.3.2.10) to determine the minimum\nratio between the yield strength of the material and the design stress. In § 178.274 (c)(2) the\ndesign margin is equal to 1.5; therefore, the minimum ratio is 1.5. Additionally, please note\nthat an approval agent must evaluate the design and calculations for UN Specification portable\ntank as required by § 178.273(b).\nI hope this information is helpful. Please contact this office should you have additional\nquestions.\nSincerely,\nT. Glenn Foster\nChief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division\n\n<<<PAGE 2>>>\n\nDrakeford, Carolyn (PHMSA)\nFrom: INFOCNTR (PHMSA)\nSent: Monday, September 13, 2010 10:26 AM\nTo: Drakeford, Carolyn (PHMSA)\nCc: DerKinderen, Dirk (PHMSA)\nSubject: FW: Request for Formal interpretation to the \"Design Margin\" in Section 178.274 (c)(2) for UN\nportable tank design criteria\nHi Carolyn,\nWe received the following request for a formal letter of interpretation at the Info\nCenter.\nThanks,\nVictoria Lehman\n202-366-1035\nFrom: Wang, Jianke [mailto:Jianke.Wang@nov.com]\nSent: Friday, September 10, 2010 4:23 PM\nTo: INFOCNTR (PHMSA)\nSubject: Request for Formal interpretation to the \"Design Margin\" in Section 178.274 (c)(2) for UN portable tank design\ncriteria\nDear Sir/Madam,\nIn Section 178.274 (c )(2) for UN portable tank design criteria, there are\n\"(2) Under each of the forces specified in paragraph (c}ll) of this section, the safety factor must be as follows:\n(i) For metals having a clearly defined yield point, a design margin of 1.5 in relation to the guaranteed yield strength; or\n(ii) For metals with no clearly defined yield point, a design margin of 1.5 in relation to the guaranteed 0.2% proof strength and, for austenitic steels, the 1 % proof strength.\n\"\nWhat is the definition ofthe \"design margin of 1.5\"?\nTo my knowledge, a \"design margin of 1.5\" could result in a safety factor of 2.5 (1.5+ 1 =2.5).\nYour response will be appreciated.\nBest regards,\nJianke Wang, Ph.D., P.E.\nSenior Project Engineer\nISO Vibration Analyst IV\nNational Oilwell Varco\n2800 N Frazier St\nConroe, TX 77303\nTel: 936-523-2634\nFax:936-523-2788\n1","truncated":false,"body_characters":3620}