The people performing the work had reached a stopping point to let the injected compounds firm up to create the seal. The work team left the cubicle in which the work was being performed in order to cool off, the temperature in the cubicle being too high to allow them to stay there. A patrolling security guard entered the cubicle and noticed a small flame on the valve. Appropriate personnel were notified and the flame was put out with a fire extinguisher. The compounds used to seal the leak were approved products for the application and are in common use in the industry.
Mineral oil is one of the material components of the compound.
When the compound is injected under pressure and gets hot, the mineral oil tends to separate from the rest of the compound, becoming more fluid and starting to leak out wherever it can find a path. In this event, the mineral oil leaked out from the sealant-retaining clamp as a liquid and soaked into the fiberglass insulation around the valve. 1997 Page 2 of 2 lowered sufficiently to ignite the oil and produce small flames on the insulation pad. Porous materials, such as blanket-type insulation, exhibit a wicking effect when exposed to a combustible liquid. An outside ignition source is not required for combustion to occur in oil-soaked insulation.