PDL56 series hazard?

[Magnus Forteman]

Hello everyone, a bit of an odd one here:
Long story short, I've been tagging this guy's gear for a while. He rings me up saying one of his staff has received a shock while unplugging 3-phase lead, can I please check it out. Standard 56 series plug and socket, older screw-together type.
Lead passes continuity and insulation resistance P-E etc, visually nothing obvious, I'm about to clear it when I had the sudden urge to test from phase to the two mounting screws.
Sure enough, there's direct continuity from one of the screws to A-phase. Pull the plug apart to find some clown had stripped the outer sleeving way too far, and pinched the phase wire between the front and rear of the plug, and to top it all off put the mounting screw directly through the phase wire. (will try upload pic, though I'm sure you get the idea)

Couple questions: has anyone ever come across something like this before?
Should the mounting screws on plugs etc be tested as part of 3760 or similar? Bear in mind it's an extension lead, should exposed metal be bonded (good luck with that) or is the plug more like a class II?
The staff member got cleared medically, thankfully, though still annoyed.

Any thoughts, suggestions or questions would be very welcome...

[AlecK]

If assembled in accordance with manufacturer's instructions; there's plenty of insulation between the screw and any live parts.
First a layer of plastic of the plug body, and then an air gap, and then the insulation of the conductor.
So clearly Class II.


In this case MI's have NOT been followed, and no care at all has been taken in assembling the plug.
I suspect it was assembled - unlawfully - by an unlicenced person.


Also the heads of these screws are recessed / shrouded; so can't easily be touched unless the plug body has been damaged.
Which would fail visual inspection under "3760".
[2.3.2(a); obvious damage, defects]

[Magnus Forteman]

Thanks AlecK, I completely agree that if the plug had been terminated and assembled correctly, there wouldn't have been a problem. I'm fairly sure that this particular plug was re-terminated by a demolition worker...

Not sure I agree with the screws being recessed as such. There's a bit of raised plastic around the screw head, but they're actually rather easy to touch on an undamaged plug.

So no obvious visual damage. The only visual 'defect' would be that the clear plastic housing was no longer very clear, though I'm not sure that plug transparency is a pass/fail criteria, but more of a 'nice to have'.

They don't seem to pass the "finger test", which is why I was wondering whether this should fall under the 'exposed metal' category for the purposes of testing class II - something I'd never considered before. Or if not, why not?

[AlecK]

2bd look at one i have here, this time with glasses,
agree the screw head isn't recessed into a shroud as I thought .

So the screw is an "accessible conductive part".
But it isn't "liable to become alive", as there is double insulation between it and any live parts.

So not ECC test of "accessible earthed parts" of Class I equipment" as per 2.3.3.1

But yes, would need to be IR tested as "accessible metal part" of Class II, as per Table 2
same as a drill chuck.

Another example of an 'extra' test required by the Standard but not automatically done by any PET machine
I 'll bet nobody actually does this test
I used to do a fair but of PAT for industrial customers; but I never thought to actually test these screws.
And i thought i was doing a thorough job.

[Magnus Forteman]

Thanks again, I'm wondering whether anyone in NZ actually IR tests these screws?