Railcar shunt causes Propylene release

Accident summary

There were six stationary railcars in a loading bay. One of the railcars was empty whilst the remaining five all contained propylene. One of the full tankers had been overfilled, and was connected by hoses to the loading bay fixed pipework so that it could be partially emptied. The car valves were open but the fixed loading bay valves were closed. A further five full railcars were on this line. The end car was obstructing the track points for access to other loading bays. Either through lack of communication or misunderstanding, the locomotive crew believed that the propylene train was ready to be moved, and decided to shunt the five full cars further down the line to clear the track points. The train was moved approximately five feet, which was sufficient to break both the liquid and vapour stubs on the connected railcar. About 10 tonnes of propylene were released over a period of eight minutes.

The emergency services were called and attempts were made to close the foot valve hydraulically. This failed and an operator had to enter the vapour cloud and close the block valves on the railcar manually. Fortunately, the cloud did not ignite, but the operator sustained cold burns.

Failures in technical measures

• Standing instructions, which covered the movement of railcars, prohibited the shunting of the number of railcars involved in this incident (nine in total).
• Roadways / Site Traffic Control / Immobilisation of Vehicles: control of vehicle movements
• The stationary railcar obstructing the track points was equally left in a position of risk of a collision.
• Roadways / Site Traffic Control / Immobilisation of Vehicles: control of vehicle movements
• The failure to close the foot valve using the hydraulic system meant that an operator had to enter the gas cloud sustaining injury.
• Isolation: remote emergency isolation
• Emergency Response / Spill Control: emergency operating procedures

References

Tony Fishwick, 'Railcar Shunt Causes Propylene Release', Loss Prevention Bulletin, Issue No. 146, April 1999, p 19, Institution of Chemical Engineers, ISSN 0260-9576.