All of us have seen signs at filling stations warning us not to use cellphones while filling our tanks. There’s a simple reason behind the regulation: As liquids or vapors pass through pipes or hoses, they generate static electricity, and a static discharge can easily ignite flammable vapors in the area. This example from everyday life is worth remembering in the specialized world of tank degassing, where vacuum trucks are used to control vapors at refineries and other facilities. Every vacuum truck in the world uses pipes and hoses to degas tanks and other vessels, and these connections can accumulate substantial static charges during the degassing process. The good news is these charges can be safely controlled using techniques known as bonding and grounding.
Bonding is ensuring every connection in an electrical process is bonded — or “connected” — to provide a pathway for an electrical charge to follow. In degassing operations, every section of pipe and every connection represent a “link” that contributes to a solid electrical connection between the tank and the vacuum truck. This collection of bonds is only as strong as the weakest link, and if one connection fails, the entire chain is broken. Instead of traveling through a pathway of secure connections and being safely grounded, the electrical charge essentially stops at the broken link. The result is an unsafe situation, which can lead to an electrical discharge that can ignite flammable vapors.
Grounding is the second part of the electrical safety process, and it ensures an electrical charge can be safely dissipated. Refineries and other large facilities typically include grounding stations that are certified to handle very large electrical loads. But if a grounding station is not available, vacuum truck operators have a number of other options to ensure electrical charges can be safely distributed to the ground. Using a device known as a fluke meter, operators can quickly identify the best way to create a proper ground for their degassing operations.
I make dozens of presentations every year on proper bonding and grounding procedures and always emphasize three key points. First, under certain conditions, even relatively low flow rates can create alarmingly high levels of voltage. In other words, even a seemingly “simple” degassing operation can create enough static electricity to ruin your day. Second, unsafe techniques such as “splash filling” during tank loading can quickly generate static charges. Knowing how electrical charges can accumulate is an important step to ensuring safety throughout the degassing process. And third, I always emphasize there is no substitute for personally checking each part of the bonding and grounding circuit. Before any degassing process begins, the best operators “walk the line” to personally confirm every pipe, connection, clamp and cam lock. They use an ohmmeter to confirm the integrity of every connection and a fluke meter to verify electrical charges will be safely dissipated into a grounded connection. The best degassing companies require their operators to record all their findings in a degassing log that is provided to the client after every job.
My presentations also include a brief outline of what can go wrong if proper bonding and grounding procedures are not followed. An improperly grounded vacuum truck is believed to have contributed to a fatal explosion at a refinery in Europe, and numerous examples exist of how static discharges have ignited vapors in the U.S. Proper training on bonding and grounding procedures is a proven way to prevent accidents and ensure the safety of everyone involved in degassing operations. If you are responsible for HS&E performance at your facility, I strongly recommend training your field operators on these proper bonding and grounding techniques. The bottom line is you should promote safety for all degassing operations and commit to doing everything you can to ensure proper bonding and grounding.
For a copy of Maverick Field’s slide presentation on safe bonding and grounding techniques, call (281) 715-2900, Ext. 292 or email maverick.field@envent.net.