Structure grounding

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rquin

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I am in an industrial environment and I have asked to come up with some references for our grounding practices. I-beam type structures for piping or other loads are grounded every 60 feet if tied together with beam construction. I-beam supports that are not or stand alone we require those to be grounded also. I have searched the NEC and have not come up with anything. Does anyone know if this is referenced in the NEC or not?
 
"Grounds for Grounding", Joffe and Lock, IEEE Press, is a very good overall reference on grounding theory and practice.
 
This talks about structural steel for buildings. Do they consider building structure the same as pipe racks and you have a lot of single structures not tied together with other structures.
 
What is the question here. If you have structural steel that has portions of it's "footing" direct buried or encased in concrete and is electrically continuous to other structural steel - it is all "grounded". All that is left for consideration for most electricians is bonding that to the electrical system grounding elecrode system, and all you typically need is one point of bonding with an appropriate size conductor in relation to the service or feeder conductors that supply that building or structure.
 
Unless it meets the definition of a grounding electrode, I don't believe there is a specific requirement to ground or bond it. It could be specified to have additional bonding or grounding for various reasons. Depending on the piping on the racks, I could see this being to dissipate static charge.

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kwired said:
What is the question here. If you have structural steel that has portions of it's "footing" direct buried or encased in concrete and is electrically continuous to other structural steel - it is all "grounded". All that is left for consideration for most electricians is bonding that to the electrical system grounding elecrode system, and all you typically need is one point of bonding with an appropriate size conductor in relation to the service or feeder conductors that supply that building or structure.
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I would consider electrically continuous being tied together with other structural steel other than just one sitting alone. Piping and cable tray "sitting" in the rack, I do not think it would be considered electrically continuous. Our company requires that all stand alone (without a structural connection) as having to be grounded. I am currently trying to find an IEEE document to address this.
 
rquin said:
I would consider electrically continuous being tied together with other structural steel other than just one sitting alone. Piping and cable tray "sitting" in the rack, I do not think it would be considered electrically continuous. Our company requires that all stand alone (without a structural connection) as having to be grounded. I am currently trying to find an IEEE document to address this.
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Make sure you understand the concepts of grounding and bonding. It sounds like bonding is what mean, and not necessarily grounding.
 
rquin said:
I would consider electrically continuous being tied together with other structural steel other than just one sitting alone. Piping and cable tray "sitting" in the rack, I do not think it would be considered electrically continuous. Our company requires that all stand alone (without a structural connection) as having to be grounded. I am currently trying to find an IEEE document to address this.
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Are you looking for a code to affirm the company requirement? I don't think you'll find it.

Are you looking for best practices to accomplish the requirement? It would help to have more information if this is the case. What are you mitigating? Is this a ESD matter to protect sensitive electronic components or assemblies? Is this an electrocution mitigation measure?
 
rquin said:
I would consider electrically continuous being tied together with other structural steel other than just one sitting alone. Piping and cable tray "sitting" in the rack, I do not think it would be considered electrically continuous. Our company requires that all stand alone (without a structural connection) as having to be grounded. I am currently trying to find an IEEE document to address this.
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Are you trying to address electrical system grounding requirements, mitigate static, comply with grounding/bonding requirements for certain materials/conditions that may not be electrical system related?

I don't see NEC specifically requiring you to bond isolated sections of building steel unless they are likely to become energized. It does require a grounding electrode conductor to building steel but doesn't mention any requirement of bonding to other isolated sections of building steel either.
 
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