Although static electricity can be regarded as a difficult subject to grasp, we hope that the information in this article can give you a better insight into the reasons why static electricity is a credible ignition source and what practical measures, based on internationally standards and recommended practices, can be taken to remove the fire and explosion risk it represents for your operations. In this incident a vacuum truck deployed to remove a below grade sump that contained mostly “off-spec” toluene. As the operation was nearing completion of the removal of toluene an ignition of the vapours occurred resulting in a fire. In the ensuing investigation of the incident it was determined that the vacuum truck had not been grounded by the operator. Although other ignition sources would have been considered, the fact that the truck was not grounded and the material being transferred was toluene, it was highly plausible that a static spark was the cause of the fire.
Getting the grounding right – grounding is not simply connecting the truck to something that looks like it’s entering the ground. Careful consideration needs to be placed on the method of grounding and what parameters can be implemented so that a constant connection to ground is maintained for the duration of the operation.