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Checking earthing on sections of a factory production machine

CarloUK

Hello,

I work in a production factory where we have machines that have multiple sections. The machines have been installed by professionals and the incoming earth to it checked annually.

I want to regularly check that all sections of the machine is earthed/bonded to the machines main earth incoming cable.

How is this done. Do we just resistance check from the incoming earth to each section. If so what is an acceptable resistance. ie Less than 0.5 ohms ?

Thanks Carlo

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  • What is "low enough" rather depends on the credible fault current, and that you can probably estimate from the current rating of the equipment in question and then a large factor for safety perhaps ten, so  say you had a 32 A supply, assume you' like an earth path that can take 320A or more to operate a breaker smartly, so your half ohm figure is about right, but on the other hand, for a thing enclosing a 200A supply it may not be good enough.

    Arguably bits of the machine that do not come anywhere near any wiring, and there is no credible fault path that would make it live, are less important - so small access panels to lubrication points or something that are nowhere near any wiring, are not really worth worrying about.

    Mike.

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  • What is "low enough" rather depends on the credible fault current, and that you can probably estimate from the current rating of the equipment in question and then a large factor for safety perhaps ten, so  say you had a 32 A supply, assume you' like an earth path that can take 320A or more to operate a breaker smartly, so your half ohm figure is about right, but on the other hand, for a thing enclosing a 200A supply it may not be good enough.

    Arguably bits of the machine that do not come anywhere near any wiring, and there is no credible fault path that would make it live, are less important - so small access panels to lubrication points or something that are nowhere near any wiring, are not really worth worrying about.

    Mike.

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