One CIS Insurance Company — Hazardous Materials Safety Interpretation

Page 1Mr. Edgar A. Whittle Director, Codes & Standards One CIS Insurance Company Reference No. 16-0130 Dear Mr. Whittle: This letter is in response to your July 20, 2016, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180) applicable to thickness testing and repair of a DOT Specification MC 331 cargo tank. Specifically, you provide a scenario in which an MC 331 cargo tank shows corroded, gouged, or abraded areas and ask to what minimum thickness the tank should be tested and repaired. Section 180.407(i)(4)(ix) requires that thickness testing be performed on known thin areas of the tank shell, which could include those that are corroded, gouged, or abraded. As specified in § 180.407(i)(9), an MC 331 cargo tank built before October 1, 2003, must be thickness tested to a minimum thickness based on the U1A form, minus any corrosion allowance. For an MC 331 cargo tank built on or after October 1, 2003, the minimum thickness is the value indicated on the specification plate. In accordance with the acceptable results of tests and inspections in § 180.411(a) and (b)(2), corroded or abraded areas—as well as dents, cuts, digs, and gouges- should have a minimum thickness no less than the prescribed specification, which in this case is an MC 331 cargo tank. Please note that § 180.407(b)(1), (d)(5), and (e)(3) specify that corroded or abraded areas must be thickness tested in accordance with § 180.407(i)(2), (i)(3), (i)(5), and (i)(6). For consistency, paragraphs (b)(1), (d)(5), and (e)(3) should also reference paragraph (i)(9) as it provides thickness specifications for MC 331 cargo tanks. This issue will be addressed in a future rulemaking. I trust this information is helpful. Please contact us if we can be of further assistance. Sincerely Chief, Standards Development Branch Standards and Rulemaking Division#

Page 2July 20, 2016 Standards and Rulemaking Division Pipeline and Hazardous Material Safety Administration East Building, 2nd Floor Washington, D.C. 20590-0001 Attention: PHH-10 Request for Interpretation Reference: 178.337-17(b)(9) and (11) Subject: Minimum Thickness stamping on manufacturers specification plate Gentleman: Please provide clarification for the term "minimum thickness" as related to the manufacturers specification plate for MC-331 cargo tanks et. al. The regulation, 178.320, defines minimum thickness as the thickness necessary to meet structural integrity or the thickness as computed per the ASME Code requirements. If the computed minimum thickness value is intended to be used as an "Out of Service thickness", , this value does not give consideration to ASME's UG-16 for Mill Undertolerance, Mandatory Appendix 32 for Local Thin Areas or material that is rolled by the steel mill that may be thicker than the ordered thickness. Question: If it becomes necessary to restore material thickness due to corrosion, gouges or abraded areas, what thickness is to be used to gauge the depth of these conditions and what thickness should the material be restored too? Please contact me if you have any questions. I may be reached via phone at 781-584- 1104/fax: 781-584-1119 or email: ed.whittle@onecis.com. Edgar A. Whittle, Director, Codes & Standards#