Bonded, Grounded, and Burned to a Crisp: Electrostatic Ignition of Flammable Gases

Ignition by electrostatic discharge of clean flammable gas, such as natural gas, being released to the atmosphere during blowdown operations is unlikely. However, the presence of foreign material in the form of solid particles or liquid droplets changes the risk level significantly. The discharge of a flammable gas stream with a cloud of foreign material poses a potential electrostatic hazard, even if the piping system and associated equipment is otherwise bonded and grounded. The foreign material may be capable of accumulating sufficient electrostatic potential to ignite the flammable gas. There have been several documented incidents where ignition has occurred during a flammable gas blowdown. In some instances, gas lines were being cleaned, while in others, the blowdown was completed as a safety measure for another process. This article will focus on a case study where a stream of flammable gas was ignited during a blowdown and an obvious ignition source (other than electrostatic discharge) was not present, but foreign material was observed. (c) 2018 American Institute of Chemical Engineers Process Saf Prog 38: e12024, 2019