Tank Trailer Grounding

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ilmzj

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We are building an over-the-road tank trailer to transport non-flammable liquid to a customer site. There is a 7.5 HP, 460VAC, 3PH agitator motor that the customer energizes through a Meltric connector ahead of the combination starter / disconnect.
We have checked and there does not appear to be DOT requirements for tank trailer grounding at the customer site during unloading.
We have found NFPA 385 (Standard for Tank Vehicles for Flammable and Combustible Liquids).

We are wondering about the NEC requirements for tank trailer grounding for non-flammable liquids.

All comments / suggestions / direction is appreciated.


Thanks,

John
 
Re: Tank Trailer Grounding

None. The NEC does not apply see section 90.2 (B)
(B) Not Covered. This Code does not cover the following:
(1) Installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles.

However if it is subject to becomning energized, then the trailer frame could be bonded to provide am effective ground fault return path per 250.4(A)(4). Are there DOT requirments that may apply? Personally I would bond it to the equipment grounding conductor....
 
Re: Tank Trailer Grounding

Tom,

Thanks for your response. A follow-up or clarification please.

Referencing 250.4, will the bonding conductor through the 4 pole plug/jack connection (Meltric) be considered an adequate bond?
Or, would a separate "dedicated" bonding cable be required or considered "good practice"? The separate "dedicated" bond would in effect provide two (2) bonding / ground fault current path back to the electrical supply source ground.

Once again, all comments / suggestions / direction is appreciated.


Thanks,

John
 
Re: Tank Trailer Grounding

I would not add the second bond, that would divide any fault current and increase the impedance of the circuit. You want all the circuit conductors to be in close proximity. The Meltric connector will be OK as its a listed product.

[ April 12, 2004, 10:58 PM: Message edited by: tom baker ]
 
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