My plant is an old multistory wood and brick structure. Many years ago, someone began putting steel plates on the floor to save the wood flooring from damage as equipment and pallets were moved across the floor. A new project is at hand, and now there is a plan to put new floor plates in. My question: Should these steel plates be tied to the plant ground system? What about grounding the existing plates? As I read 250.4 (A)(4), if these plates are likely to become energized, they need to be connected to ground. I can imagine that a portable extension cord could be laying across the floor and could be rolled over by a cart, hand truck, dumpster, etc, possibly damaging the insulation. I can also envision a ground fault in a piece of equipment setting on these plates. Thanks for your opinions on this matter
Industrial Plant Grounding/Bonding
- Thread starter KC_EE
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- Massachusetts
Re: Industrial Plant Grounding/Bonding
In my opinion it is not required but a good idea.
If the plates butt each other a simple tack weld between each plate should bond them together than find someplace easy to jump one plate to a grounding means.
In my opinion it is not required but a good idea.
This should not be an issue as that equipment should have it's own EGC.
If the plates butt each other a simple tack weld between each plate should bond them together than find someplace easy to jump one plate to a grounding means.
Re: Industrial Plant Grounding/Bonding
Bob:
Thanks for your response. Welding the plates together historically has not worked here. This has been tried in the past, and the two issues encountered with that method are that the welds never last (they break due to the traffic of the various material handling fork trucks, dollys, etc. causing the weld to be stressed as they roll from plate to plate), and the thermal expansion of the now large steel plate assemblies causes the plates to buckle. And as for the EGC, it is true that each piece of equipment has its own EGC. I omitted that our plant uses a high resistance ground connection for our substation transformer. A ground fault on any equipment connected to our main substation will cause the ground fault current to flow through the EGC back to the transformer through the grounding resistor. Until the fault is located and cleared, the equipment will exhibit a voltage to ground, which I believe qualifies as "energized". The metal plate under the equipment may then become energized. Any more opinions/ideas?? Thanks again for reading and replying to this post.
Bob:
Thanks for your response. Welding the plates together historically has not worked here. This has been tried in the past, and the two issues encountered with that method are that the welds never last (they break due to the traffic of the various material handling fork trucks, dollys, etc. causing the weld to be stressed as they roll from plate to plate), and the thermal expansion of the now large steel plate assemblies causes the plates to buckle. And as for the EGC, it is true that each piece of equipment has its own EGC. I omitted that our plant uses a high resistance ground connection for our substation transformer. A ground fault on any equipment connected to our main substation will cause the ground fault current to flow through the EGC back to the transformer through the grounding resistor. Until the fault is located and cleared, the equipment will exhibit a voltage to ground, which I believe qualifies as "energized". The metal plate under the equipment may then become energized. Any more opinions/ideas?? Thanks again for reading and replying to this post.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Industrial Plant Grounding/Bonding
There are flat braided straps available and with slack left in the connection should hold (in an industrial environment the may need to be inspected periodically), these could be cad welded or bolted to the plates.
The danger of an ungrounded metal plate would be the same as a manhole cover and there are several items in this forum discussing that issue.
[ May 10, 2005, 11:16 AM: Message edited by: brian john ]
There are flat braided straps available and with slack left in the connection should hold (in an industrial environment the may need to be inspected periodically), these could be cad welded or bolted to the plates.
The danger of an ungrounded metal plate would be the same as a manhole cover and there are several items in this forum discussing that issue.
[ May 10, 2005, 11:16 AM: Message edited by: brian john ]
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