Fire Engineer

This paper deals with the fire accidents caused by static electricity during handling of nonconductive flammable liquids in chemical & petroleum installations. It offers some basic information on the origin of static electricity in different environment. It also gives some less known facts about this always present danger and illustrates, through examples from practice, consequences on process & business establishment. Static electricity is a phenomenon of great importance when handling solvents, and in particular, hydrocarbon solvents. It is one of the least understood and a most difficult ignition source to control. Similar operations can produce different levels of static charge on different conditions, which may ignite solvent vapors, if present. Industries that handle, transfer, and store nonconductive flammable liquids, such as naphtha, toluene, benzene, xylene and heptane, should take extra precautions beyond normal bonding and grounding to avoid an incident. When a liquid with conductivity less than 50pS/m, there should be enough residence time required between the filter/screen and the point of discharge to allow sufficient charge relaxation. A relaxation volume can be provided between a charge generator such as a micro filter and a tank so that the residence time is sufficient for charge to relaxto safelevel. Twelve liquid tank accidents over a period of 45 years, caused by static electricity were reviewed.Three case studies of major explosions in tank farm area & one aircraft hanger fire caused due to static electricity were analyzed to find out preventive measures. Preventive measures for fire and explosion protection due to static electricity in certain operations in these installations are also discussed. The causesand the contributing failures that led to accidents due to static electricity were expressed with the Ishikawa diagram in a systematic way. Most of those accidents would have been avoided if good engineering in design, construction, maintenance and operation has been practiced and safety management program has been implemented and executed.