Flammable vapors within a cargo tank are removed using mechanical air-moving equipment. As outside air is introduced into the cargo tank, the vapor/air mixture within the tank, and near the tank openings, will fall into the flammable range. During this time, if the air moving equipment used to gas free the cargo tank is not the proper type, is not properly maintained, or is not properly electrically bonded and secured to the vessel’s structure, static electricity generated by the air moving equipment can discharge as an electric arc and ignite the flammable vapor/air mixture. This post provides guidance to vessel owners/operators about the proper procedures to prevent potentially deadly explosions.
Source: Investigations & Casualty Analysis
Link: Improper bonding during gas freeing leads to dangerous results