C13/1999R Hazardous situation generated by detaching of brake triangle in tank wagon at Humppila on 18 September, 1999

On 18 September 1999, a hazardous situation arose at Humppila, Finland, when the other brake-triangle end in a tank wagon detached and dropped between the rails, breaking, e.g. the wooden decks of four level crossings over a distance of five kilometres. The tank wagon was loaded with phosphoric acid. The train came to a full stop at the fourth broken level-crossing deck when its planking opened the coupling hose of the brake conduit and thus activated emergency braking.

The brake triangle of the tank wagon detached and dropped between the rails as the joint-pin clamping cotter of the upper end of the brake triangle bracket had worn excessively as due to vibration. The cotter had broken and the pin was displaced.

In order to prevent corresponding hazardous situations and possible incidents, the Accident Investigation Board of Finland recommends that if essential modifications are carried out in wagon superstructures in connection with their reconditioning, the specific frequencies of the wagons should be calculated and whenever possible, also checked by testing, prior to the approval of the wagon for introduction into traffic. Furthermore should any irregular wear be detected in the equipment of a separate wagon or wagon type in traffic, the wagon should be submitted to special monitoring and extra maintenance measures; the cause of the wear should be investigated and remedied, and if required, structural changes should be realized in the wagon to eliminate such irregular wear and to ensure a safe travelling of the wagon.

The Accident Investigation Board of Finland also underscores that an alarm signal emitted by a hot-box detector must always be taken seriously. The cause of the alarm must always be discovered before the train is given permission to continue.

C13/1999R Report (pdf, 0.56 Mt)

  • Recommendation S163
  • Recommendation S164
  • Recommendation S165
Published 18.9.1999