Requirements for a minimum ignition energy standard

Fires and explosions are serious hazards in the process industries. Mitigation methods, such as suppression and venting, can be expensive. Ideally, the best option would be to avoid fire or explosion, which may be accomplished by either removing the explosible fuel/oxidant mixture, or the ignition source. One of the most overlooked and preventable ignition sources is electrostatic discharge (ESD). To evaluate the potential for ignition of a fuel/oxidant mixture, one must determine its minimum ESD ignition energy. Once the initiation thresholds have been identified, one can evaluate the likelihood of electrostatic charging and storage, which could result in an electrostatic discharge. Identifying this threshold level can be problematic. An ASTM standard has been developed but, for this test standard to be effective, it must reflect the true hazard potentials observed in industry. Some important questions that need to be addressed to increase the utility of any minimum ignition energy standard are: (1) discharge geometry, (2) duration of the discharge and (3) calculation of the energy of the discharge. This paper will discuss the importance of these factors when evaluating the least amount of energy required to initiate an explosion.