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On August 27, 2016, about 8:26 a.m. eastern daylight time, a railroad tank car sustained a 42-inch long crack in its tank shell shortly after being loaded with 178,400 pounds of liquefied compressed chlorine at the Axiall Corporation Natrium plant in New Martinsville, West Virginia. Over the next 2.5 hours, the entire 178,400 pound load of chlorine was released and formed a large vapor cloud that migrated south along the Ohio River valley. The railroad tank car, AXLX1702, built in June 1979 by ACF Industries, Incorporated, was a 17,388-gallon US Department of Transportation specification-105J500W tank car, also known as a class DOT 105 tank car, with a stenciled load limit of 178,400 pounds and a maximum gross rail load of 263,000 pounds.
TO THE PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION: Promulgate a final standard for pressure tank cars used to transport poison inhalation hazard/toxic inhalation hazard materials that includes enhanced fracture toughness requirements for tank heads and shells.
Original recommendation transmittal letter:
Open - Initial Response Received
New Martinsville, WV, United States
Preliminary Report: Hazardous Materials: DCA16SH002
Rupture of a DOT-105 Rail Tank Car and Subsequent Chlorine Release at Axiall Corporation
Addressee(s) and Addressee Status:
PHMSA (Open - Initial Response Received)
Safety Recommendation History
-From Drue Pearce, Deputy Administrator: The Pipeline and Hazardous Materials Safety Administration (PHMSA) concurs. As you are aware, PHMSA accepted a joint petition for rulemaking (P-1691) from the American Chemistry Council, the American Association of Railroads (AAR), and the Chlorine Institute, which proposes to make final the "interim" rail tank car specifications issued as part of the HM-246 final rule, for use in the transportation of poison inhalation hazard/toxic inhalation hazard (PIH/TIH) materials. 1 The increased design specifications of the interim standard include tank-head and shell puncture resistance protection. Specifically, the standard for the puncture resistance system requires that the shell be capable of withstanding impact at 25 mph and the tank-head be capable of withstanding impact at 30 mph. The HM-246 rule was the result of government and industry consensus that an updated standard was necessary to improve accident survivability. The NTSB's report2 on the accident recommends "Charpy impact testing" as part of enhanced material toughness requirements. Such testing is not part of the interim standard. However, AAR issued a Casualty Prevention Circular (CPC) on August 1, 2005, (CPC-1170) that revised Charpy impact testing requirements for pressure cars ordered after August 1, 2005. This AAR requirement was then incorporated into its Manual of Standards and Recommended Practices (MSRP), Section C-III Specification M-1002, in 2007. PHMSA is considering incorporation by reference (IBR) of the 2014 edition of MSRP, Section C-III Specification M-1002 in a rulemaking currently in progress. PHMSA also accepted a petition (P-1646), which proposes to prohibit the use of rail tank cars with shells or heads constructed of non-normalized steel for transportation of PIH/TIH materials. Non-normalized steel is susceptible to brittle fractures at lower temperatures, and brittle fractures are far more likely than ductile fractures to result in catastrophic failure and instantaneous release of a car's entire contents. Note that such a prohibition will not capture the "highest available fracture toughness specifications" as recommended in R-19-2. However, as noted above, we are considering updating the IBR of the AAR MSRP to include enhanced material toughness requirements, and should we take this action, we will consider its effects on the prohibition under consideration with P-1646. Finally, PHMSA accepted petition (P-1692), which proposes to phase out the use of rail tank cars in PIH/TIH service that do not meet the interim standards adopted under rulemaking HM-246. To summarize, the items under consideration associated with rail transport of TIH/PIH materials include: making the interim rail tank car specifications for use in PIH/TIH service final; prohibiting the use of rail tank cars constructed of non-normalized steel; phasing out the use of rail tank cars not meeting the interim specifications; and incorporating by reference the 2014 edition of the AAR MSRP M-1002. In its report, the NTSB suggests that PHMSA "exercise its rulemaking authority to establish appropriate fracture toughness and other design criteria that minimize the loss of lading from tank cars transporting PIH/TIH liquefied gases in incidents and accidents and includes a timely risk-based implementation schedule." PHMSA expects the proposed changes identified in P-1646, P-1691, and P-1692 (discussed above) to enhance the safe transport of PIH/TIH materials in a manner that is consistent with the NTSB recommendations, but PHMSA will continue to monitor the extent to which these changes result in improved safety and will consider additional rulemaking actions if necessary. Furthermore, we understand the NTSB's concern that economic factors alone should not drive PHMSA's decision-making with respect to an appropriate phase-out schedule for tank cars not meeting the enhanced interim standards being considered for implementation as final. As with all proposed rulemakings, PHMSA must comply with Executive Order (EO) 12866.3 As part of its EO 12866 compliance, PHMSA assesses the costs and benefits of alternatives but recognizes that the economic analysis is only one factor to consider in rule decision-making. This practice is consistent with DOT policies and procedures, which recognize that regulations may be necessary even when the costs exceed the benefits if such regulations are required by law or there is a compelling safety need. PHMSA will update the NTSB upon publication of the rulemaking.
On February 11, 2019, the National Transportation Safety Board (NTSB) adopted its report, Rupture of a DOT-105 Rail Tank Car and Subsequent Chlorine Release at Axiall Corporation, New Martinsville, West Virginia, August 27, 2016, NTSB/HZM-19/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, the NTSB identified the following safety issues: • Continued use of pre-1989 tank cars constructed of nonnormalized steel in chlorine and other poison inhalation hazard/toxic inhalation hazard service: According to the general requirements for pressure tank cars outlined in the Association of American Railroads (AAR) Manual of Standards and Recommended Practices, Specifications for Tank Cars, Section C, Part III, all class DOT-105 tank cars built after January 1, 1989, must have heads and shells constructed of normalized steel plate material to reduce the possibility of brittle and low-energy fracture propagation. The AAR estimated there were about 942 nonnormalized steel tank cars in use as of the second quarter 2018, and about 697 were being used to transport chlorine. ??Tank car manufacturer’s maintenance and repair instructions: Available industry guidance for inspecting and repairing ACF-200 stub sill attachments and cradle pad welds is only applicable to nonpressure tank cars. There is a need for a similar guidance document applicable to pressure tank cars equipped with ACF-200 underframes. • Postweld heat treating procedures: The tank car shop records show that following extensive corrosion repairs made to the interior surfaces of the tank shell, technicians made multiple attempts to stress relieve the repaired surfaces with local postweld heat treating. NTSB investigators found tank shell scaling, decarburization, and microstructure differences near the area of a preexisting crack that propagated and caused the chlorine release, suggesting a significantly overheated region and uncontrolled heat treatment processes. • Qualification and maintenance intervals: Safe operation of a tank car throughout its service life is contingent upon periodic inspections and testing to identify and repair cracks in critical structures before tank car integrity is compromised. Axiall Corporation based its inspection regime on the federally required maximum 10-year interval, which was too infrequent. The Axiall, Rescar, and AllTranstek failures to examine widely recognized, damage-prone inboard cradle pad weld terminations on AXLX1702 following the 2016 repairs, when the tank car was in a facility capable of conducting such inspections, was a missed opportunity to avoid the chlorine release. Accordingly, the NTSB makes the following safety recommendations to the Pipeline and Hazardous Materials Safety Administration. Additional information regarding these recommendations can be found in the noted sections of the report. • Promulgate a final standard for pressure tank cars used to transport poison inhalation hazard/toxic inhalation hazard materials that includes enhanced fracture toughness requirements for tank heads and shells. (R-19-001) (See section 2.1.1.) • Prohibit the use of those tank cars transporting poison inhalation hazard/toxic inhalation hazard materials that are constructed of nonnormalized steels and not constructed of steels meeting the highest available fracture toughness specifications, as developed from Safety Recommendation R-19-001. (R-19-002) (See section 2.1.1.) • Issue maintenance guidance to owners of US Department of Transportation Specification-105 pressure tank cars transporting poison inhalation hazard/toxic inhalation hazard hazardous materials with risk factors such as nonnormalized steel shell material and repairs or postweld heat treating near stub sill attachments and other high stress locations to (1) establish structural integrity inspection frequency, (2) provide guidance for defining critical flaw size and repair and acceptance criteria for indications in fracture-sensitive locations, and (3) provide guidance for selecting nondestructive testing methods to identify cracks with a sufficient probability of detection. (R-19-003) (See section 2.3.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number. We encourage you to submit your response to email@example.com. If your reply exceeds 20 megabytes, including attachments, please e-mail us at the same address for instructions. Please do not submit both an electronic copy and a hard copy of the same response.
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