Eathing requirements

[Monty2010]

Firstly, Hi all this is my first post,

now to business,

Background,

In cooperation with a mechanical fabrication firm we build mobile seed cleaning and treatment plant which is based on the back of an articulated lorry trailer.
This is powered by a 3 phase generator which sits on the trailer, supplying 110A. Equipment on board is a range of screw conveyors, augers, bucket elevators, shakers and gravity tables. with anciliaries such as a compressor, lighting and 240/215 sockets. The operators of the machine work both from the ground and the trailer body.

My question that i have been posed by the company we build these for, is earthing requirements.
In the past i have tied everything to the chassis, inclusive of generator, so the whole trailer is the same potential,
however the trailer sits on rubber tyres and is run while connected to an articulated lorry cab. the trailer body feet should be lowered to provide stability,
however this depends on the type of truck and trailer due to self levelling stability systems.

the ground can vary greatly for where the machine is used, from the side of a field, a concrete yard, of within a barn.

The question,

Should the trailer be grounded to the actual Earth within the area in which it stands for someone working from the floor, who will come in contact with the trailer unit.

 

[Knobhead]

A good question as a first post, you’re a rarity.

Do you fit the trailers with a flying earth lead? It’s a common practice. If used within a building this can be used to bond the vehicle to the structure. When it’s used on open ground an earth spike should be driven in to the ground local to the work area.
Another member Engineer54 will give the best information when he comes on. So give him a while to catch up.

 

[Sintra]

As Tony quite rightly states the chassis should be fitted with a fly lead.

 

[Engineer54]

A good question as a first post, you’re a rarity.

Do you fit the trailers with a flying earth lead? It’s a common practice. If used within a building this can be used to bond the vehicle to the structure. When it’s used on open ground an earth spike should be driven in to the ground local to the work area.
Another member Engineer54 will give the best information when he comes on. So give him a while to catch up.

Can't give any better advice than already given above by Tony. There isn't much more that can be done with a temporary situation such as you describe. These flying leads are nearly always provided by a mounted cable reel with a flexible 16mm tri-rated cable with a heavy duty crocodile jaw/clamp type connection....

 

[Monty2010]

Thank you all for your answers, I have to make a visit this company today so at least i can go weighted with an informed answer.

To answer your questions, no we have never fitted the trailers with a flying lead but it was a consideration, due to the original machines never being fitted with such an earthing provision it never came to mind as a consideration. the original machines were built early nineties and for this reason i guess the earthing was not at a standard as we work today. Once brought to my attention this matter did worry me due to the potential difference between the operator on the ground touching the trailer, but luckily enough to this day one that has currently not caused an issue. we will look in to earthing all our machines now as standard practice, to prevent any nasty occurences.

Monty

 

[Knobhead]

If you take the cost of the flying lead in relation to the cost of the machine, it’s peanuts on the overall price.
I’ve got to admire you for also proposing to retro-fit them to your existing machines.
Thanks for getting back to us.
Just to add I always used 50mm welding lead fitted with Murrex welding earth clamps on our tankers. The heavy duty type dont get crushed when the driver backs over them