Pollution
Humain
Environnement
Economique

At around 9○a.m., a railway officer detected a leak on a tanker rail car parked in a marshalling yard. The tanker contained 55○t of 69% nitric acid. A dripping leak formed on a support welded onto the tank. The emergency services formed a safety perimeter of 100○m. The tanker car was routed at slow speed to its destination at a site nearby and was unloaded at 2○p.m. The operator estimated that 20○l had been released.

The expert assessment reached no formal conclusion.

The tank car was manufactured in 1983 and was made of 316Ti stainless steel. It was subject to a regulatory inspection and underwent a resistance test in 2013, without comment. The expert assessment determined that it was in good internal condition. Through-cracking, perpendicular to the circular shell/bottom weld was detected. Despite expert metallurgical analyses, the degradation mechanism was not identified. The owner of the tanker car designated several possible causes; degradation of mechanical origin (impact on the rail car) or ageing of the equipment. Finally, the thickness and roughness measurements indicated corrosion of the 316Ti stainless steel in these operating conditions, although with acceptable kinetics. However, good engineering practice recommends the use of 304L stainless steel for this type of application.

Consolidation of the Safety and Intervention Plan should an incident arise

Following an exchange with the various parties involved (port manager, locomotive operator, carman, shipper), an action plan was established, mainly aiming to:

  • Improve and strengthen communication between the parties involved;
  • Clarify the roles of certain players and raise awareness of specific hazards with regard to dangerous materials;
  • Removal from service of the rail car involved, as well as a rail car having similar characteristics.