(49c) Electrostatic Hazards: Identifying the Early Warning Signs to Reduce Explosion Risk

Electrostatic sparks are known to cause many industrial fires and explosions each year. Yet it is quite usual to find that before an incident, operators or supervisors have encountered signs that static electricity is present. These signs - the ‘early warning signs’ – had their significance been appreciated, could have prevented many industrial fires or explosions.

In this paper we bring together evidence obtained from investigation of electrostatically initiated explosions and group them by class of ‘manifestation’. We discuss how these classes/manifestations should be interpreted by reference to discharge types and their associated energy ranges. Finally, we discuss how we can go about assessing whether each static manifestation could lead to an electrostatically initiated fire or explosion as well as how they can be eliminated.

The early warning signs of static electricity can be as apparently innocuous as dust patterns on plastic or a prickling feeling on the arms. They can also include unexpected corrosion in a glass-lined vessel or even a pin-hole leak from an insulating pipe; these in addition to the well-recognized sparks and cracking sounds that present themselves as the more obvious face of hazardous static electricity.

Waiting for an ‘early warning sign’ can never be a substitute for the detailed hazard assessment work that focuses on the identification and elimination of all potential ignition sources. But it is worth noting that electrostatic sources of ignition are often considered to be more complicated to identify and eliminate than others, and consequently, they frequently elude the formal HAZOP or hazard study process. With electrostatic hazards, this makes vigilance by operatives and others that much more important, especially since electrostatic effects can easily be spotted and eliminated - if you know what to look for. The new proposed ‘classification’ can aid understanding of hazardous static electricity and thus help reduce the risk of fire and explosion in industry.