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Safety Recommendation Details

Safety Recommendation R-19-004
Details
Synopsis: 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. The tank car was equipped with an ACF Industries, Incorporated ACF-200 stub sill underframe design, which the Federal Railroad Administration has previously noted in a 2006 safety advisory as being prone to defects such as tank head cracks, pad-to-tank cracks, sill web cracks, and tank shell buckling that in some instances has led to release of hazardous materials. Rescar Companies received the tank car in January 2016 to conduct a 5-year interior inspection required on chlorine tank cars in accordance with Axiall Corporation maintenance instructions. Inspectors revealed many corrosion pits across the bottom of the tank shell. AllTranstek (Axiall Corporation’s maintenance administration contractor) approved repairs that were made at that time. The tank shell crack and chlorine release occurred following its first postrepair loading. The National Transportation Safety Board initiated this investigation to examine the performance and structural failure of the DOT-105 tank car. The shell failure was consistent with crack propagation from a preexisting, undetected crack, and the presence of stresses induced by uncontrolled postweld heat treating, shell buckling, and low temperature lading. This report focuses on 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 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 Association of American Railroads 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. National Transportation Safety Board 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.
Recommendation: TO THE ASSOCIATION OF AMERICAN RAILROADS: Implement revisions to the American Association of Railroads Manual of Standards and Recommended Practices Specifications for Tank Cars, M-1002 to ensure that local postweld heat treatment processes are sufficiently monitored to avoid damage to tank car materials from uncontrolled heat treatment following welding and repairs.
Original recommendation transmittal letter: PDF
Overall Status: Open - Await Response
Mode: Railroad
Location: New Martinsville, WV, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA16SH002
Accident Reports: Preliminary Report: Hazardous Materials: DCA16SH002Rupture of a DOT-105 Rail Tank Car and Subsequent Chlorine Release at Axiall Corporation
Report #: HZM-19-01
Accident Date: 8/27/2016
Issue Date: 2/14/2019
Date Closed:
Addressee(s) and Addressee Status: Association of American Railroads (Open - Await Response)
Keyword(s): Hazmat

Safety Recommendation History
From: NTSB
To: Association of American Railroads
Date: 2/14/2019
Response: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge your organization to act on the safety recommendation in this letter because we believe your organization can help reduce the risk of future accidents. For more information about NTSB and our recommendation process, please see the attached one-page summary. On February 11, 2019, the 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 recommendation to the Association of American Railroads. Additional information regarding this recommendation can be found in the noted section of the report. ??Implement revisions to the American Association of Railroads Manual of Standards and Recommended Practices Specifications for Tank Cars, M-1002 to ensure that local postweld heat treatment processes are sufficiently monitored to avoid damage to tank car materials from uncontrolled heat treatment following welding and repairs. (R-19-004) (See section 2.2.1.) The NTSB is vitally interested in this recommendation because it is 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 this recommendation. When replying, please refer to the safety recommendation by number (for example, R-19-004). We encourage you to submit your response to correspondence@ntsb.gov. 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.