Ground Rod

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sportster

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MSHA,( Mine Safety and Health Administration) inspected a portable rock crusher in a gravel pit. The unit is 3 phase 240V and the generator is power by a diesel motor mounted on the machine. All conveyers and electric motors are mounted on the unit along with the control box and motor starters. They had me put 2 ground rods, one bonded to the frame, and the other bonded to the control box. I'm confused and hope someone out there can explain there reason for the ground rod instalation. ( They got there Ground Rods)
 
Re: Ground Rod

Does the NEC apply?
90.2(B)Not Covered. This Code does not cover the following:
(2)Installations under ground in mines and self-propelled mobile surface mining machinery and its attendant electrical trailing cable
 
Re: Ground Rod

I don't think NEC applys. I guess my question is I don't understand the reason for the ground rods? Everything I read says power will go back to the source, with is all connected on the same unit. I appreciate you guys knowledge
 
Re: Ground Rod

I did some work in a mine some time ago,MSHA has some of there own regs beyond NEC & OSHA , maybe we should find there regs and see what they say.
 
Re: Ground Rod

Static (as mentioned is a major concern in a mine,
Lightning might be an issue in a open pit.
Reviewing MSHA rules would be the best bet..........but for my money a misunderstanding of how grounding systems are properly installed and how a electrical distribution system works.
 
Re: Ground Rod

Idon't understand how static would be an issue? Static from what and what does a connection to Earth do? If the equipment has proper equipment bonding, wouldn't that eliminate the static issue?
 
Re: Ground Rod

I doubt static has anything to do with it.
They are surely not blasting anywhere near this equipment.

My guess is misunderstanding grounding and bonding.

Why not ask the inspector?
 
Re: Ground Rod

Here's one picture of a blast that I took:


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[ July 21, 2004, 10:21 PM: Message edited by: luke warmwater ]
 
Re: Ground Rod

I asked the inspector from EMSH and he couldn't give me an answer, he was just bent on having his ground rods installed. I was more concerned with the bond between the generator and the control box and the frame work of the crusher. His request had me confused and I was worried I might have talked to him to long and lost my perspective on grounding. Sometimes it helps to see others scratch there head and raise an eye brow.
Thanks for the feed back.
 
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