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Tuesday, May 7, 2019
Question:
Morning, I read your form every day and appreciate the info. My question is static discharging for chemical barrels. A location that I noticed has the wire with the clamp then goes to a bolt for anchoring pedestrian railing to the concrete floor. There is no building steel nearby. I don’t feel that the ground path is sufficient. I suggested a ground rod and a wire ran along the lower part of the pedestrian rail. I was told an engineer said the present situation was sufficient.
Thank you, John Button
A
Answer:
Hey John thanks for your question and the compliment. Dealing with static electricity is not within the NEC Scope but is addressed by NFPA 77, Recommended Practice on Static Electricity. Chapter 7 is Control of Static Electricity and Its Hazards by Process Modification and Grounding. Bonding to minimize the potential difference between conductive objects and grounding to equalize the potential to earth is covered in 7.4.1. Grounding can be accomplished by a direct connection to an object in the earth or by bonding to another object that is already connected to the ground as stated in 7.4.1.1. Permanent or fixed grounding systems acceptable for power circuits or lighting protection are more than adequate for static electricity grounding systems as stated in 7.4.1.3.1. Other subsections of 7.4 provide additional information and references to Annex material. If the railing bolt is not connected to anything other than an anchor in the concrete its use does not seem to match the recommendations in NFPA 77.