When handling flammable liquids, preventing a fire can require a lot of planning to ensure that all equipment is properly designed and safe work practices are in place. Even though fuel, oxygen, and energy are all required to create a flame, fuel and oxygen are already abundant in most areas where flammable liquids are handled. This means that a single, small ignition source can spell disaster. There are several possible ways that a flammable vapor may be ignited; hot surfaces, power tools, and electrical devices all produce enough energy to ignite a flame under the right conditions. However, the most difficult ignition source to control is static electricity.
When two objects have different electrical charges, an electrical potential, or a potential to transfer electrical energy, is said to exist between them. If those objects approach each other, a spark can form to equalize their charges. This happens as naturally as dropping a ball to release its gravitational potential or launching a rubber band to release its elastic potential. Chances are, you have experienced a static discharge after shuffling across a carpet in your socks or sliding out of your car. In fact, rubbing two objects together is perhaps the most common way to induce static charge in an object and is known as the triboelectric effect. This is present in the chemical industry, too. Consider a liquid flowing through a pipe or a mixer running or a worker wiping down a container. Filtration is especially hazardous because of the high contact area between a liquid and the filter. Triboelectric charging is everywhere!
So, what can we do? At Superior, we employ a number of controls to help minimize static electricity in the workplace. Pumps are designed to run at lower flow rates to reduce triboelectric charging. Long filling nozzles are used to fill containers from the bottom, preventing splashing. Workers bond containers to their filling apparatus to equalize the charge before filling. We also ensure that all equipment is grounded so that any static charge that develops has a safe path away from the system. There are many strategies to combat static electrical hazards in the presence of flammable liquids, but the risk is always present and it is essential to know your part in preventing static discharges.
References
American Petroleum Institute. Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents. API Recommended Practice 2003. 6th ed. Washington, D.C.: API Publishing Services, 1998
Britton, Laurence G. Avoiding Static Ignition Hazards in Chemical Operations. New York: Center for Chemical Process Safety of the American Institute of Chemical Engineers, 1999.
National Fire Protection Association. Recommended Practice on Static Electricity. NFPA 77. 2018 ed.
