POLYMERIC BEADS: DANGER OF COMBUSTION
A recent incident of a fire on board a container ship was believed to have started when a container packed with polystyrene beads exploded. This commodity comes under UN number 2211 and gives off low volumes of pentane gas which increases as the temperature rises. Pentane gas has a very low flashpoint of -50C thus any ignition source can ignite this gas if the gas/ air mixture falls within the explosive limits. If Members are considering carrying this cargo, they should be aware of the IMDG recommendations as set out below.
The IMDG Code sets out to preventing the build up of gas from the cargo by one of two methods:
• The first is by packing the cargo into hermetically sealed packages which contains the pentane gas within the packaging and prevents it escaping.
• The second method is to pack the cargo into non hermetically sealed containment such as bags or flexible intermediate bulk containers and placing the cargo into ventilated, open top freight containers or alternatively into reefer containers designed to carry flammable gases or liquids having a flashpoint less than 23ºC and transported under temperature control. The gas is thus dispersed as it is produced and prevents any build up of gas and thus an explosive mixture cannot form. (The IMDG Code does mention the option of removing a door from the container however we would not recommend this method as this would reduce the structural strength of the container and there is also the need to crop and re-weld the door back in position. There is also the issue of the storing and securing of the container door during transport).
Members should note that standard dry containers cannot be considered as ventilated containers. The presence of ventilation pockets in standard dry containers provides passive ventilation only which is not sufficient in these cases.