TEG SOAKED INSULATION FIRE INCIDENT

A fire on an offshore installation has highlighted the risk of low temperature spontaneous combustion from TEG soaked insulation. An investigation has shown that spontaneous combustion of TEG soaked into fibrous materials can occur at relatively low temperatures (70oC). Therefore, specific precautions are required for stripping and disposal, to avoid unexpected ignition and fire.

The incident occurred on the process deck and involved removal of the aluminium cladding and TEG soaked insulation (Kaowool Ceramic) from dehydration system pipework following a small leak of hot TEG from a flange. The materials were temporarily stored, with rags used to mop up excess TEG from the deck, in a plastic sack. Spontaneous combustion subsequently caused a fire, which consumed the sack and contents.

The TEG soaked insulation was at, or near, the pipework temperature when it was placed in the plastic sack. The process of stripping the insulation allowed air to be absorbed into the insulation. In addition, dry hot insulation could have come into contact with TEG soaked insulation after being removed from the pipework.

As the insulation cooled it was possible for an oxidation process to have begun in the centre of the waste in the plastic sack, which eventually gave rise to spontaneous ignition and combustion.

This incident is an example of a well-recognised phenomenon more often observed in oil soaked rags in workshops and insulation soaked in mineral oil. It is less common in relation to TEG but can occur in the following circumstances: For spontaneous combustion to occur, TEG must be absorbed into an insulating material which has sufficient void spaces for air to be absorbed. The temperature will rise if the temperature of the insulation is relatively high and the volume sufficient to allow heat generated by an oxidation process at its centre to be retained. The larger the volume of the insulation, the greater the amount of heat retained and the lower the temperature at which spontaneous combustion of the TEG will begin. High temperatures can develop that could lead to a fire. If the bulk of TEG soaked insulation is large enough, spontaneous combustion could occur even if the insulation starts from cold. However, the time taken before the initiation of the rapid heating process would be much longer. TEG soaked rags are much less reactive than insulation, but could still present a hazard. TEG dehydration systems can run at temperatures up to 200oC and pipework is often insulated with fibrous rock wool type material. This material has a structure suited to the absorption of air into the void spaces. In normal circumstances the insulation will be clad with aluminium plate, which holds the insulation in a compressed state and prevents the ingress of air. When cladding is removed and the insulation stripped from the pipework, air will be absorbed into the insulation. If the TEG and insulation are hot from the process pipework and collected in bulk, the conditions within the stripped material can be susceptible to spontaneous combustion.

SOURCE:IOGP