Apprentice (Young Person) Training safe working voltages

Is there any specific guidance, code of practice or legislation which determines a safe working voltage for apprentices in a training facility (school)? Other than EAWR Reg 16, which states people require technical knowledge or experience, or under such a degree of supervision as may be appropriate to avoid danger. HSE INDG354 mentions as a rough guide that the use of voltages exceeding 50v ac or 120v ripple-free dc are hazardous in certain conditions.

So as an example, a first year apprentice wouldn't be expected to work on or near 240v ac (they are unaware of the risk). Only when they have gained suitable knowledge and experience through adequate training, would the risk be increased from a safe voltage. I'm not suggest apprentices can't train with 240v ac, but I would expect them to start on the theory and understand basic electrical principles before they are put at that risk. The start of an apprenticeship doesn't warrant a danger voltage to prove basic principles and electrical testing/theory.

All thoughts and opinions are appreciated.

Regards,

RJ

Parents
  • It may also be worth looking at the equality issues, as it has been noted on a Mike Holt video (USA) of at least one case where a pregnant lady was getting shocks from a poorly earthed pool fixture (common in Florida) but the potential wasn't enough for the rest of the family to comment.

    I don't know if there has been any research on the issue, but it's likely that females were never included in original research [1].

    1
    Criado-Perez, C.: ‘Invisible women: exposing data bias in a world designed for men’ (Vintage, 2020) 978-1-78470-628-9
  • Certainly Charles Dalziels work on Effects_of_Electric_Shock_on_Man despite the title, did actually include a no. of women in the study.

    "Similar data were also obtained at the Electrical Testing Laboratories, New York, on 42 men and 28 women, using four different test electrodes and 60 cycle alternating current. The ratio of average
    perception current thresholds for women to men was approximately 2/3. Thus it
    seems reasonable to conclude that the threshold of perception for women can be
    taken as 66 2/3 per cent of the corresponding value for men."

    Of course there are fewer women than men in the study,  but it does not alter the conclusion that on average, the results did indeed suggest they are more sensitive in terms of shock threshold.

    The results are more tellingly also scaled in more or less the same way for the muscle locking current levels as well.





    "Prolonged exposure to currents only slightly in excess of a person's let-go limit
    may produce exhaustion, asphyxia, collapse and unconsciousness followed by death."

    As far as I know no-one has been brave enough to publish an experimental re-validation of  these results in more recently times, perhaps with a more socially representative participant group, although the suggested safety limits are often referred to when ADS levels and RCD trip times and so on are discussed. Perhaps in a better world, these too would need two limits, based on the sex of the person to be protected - RCDs for women, with a 20mA rather than a 30mA threshold ?

    Mike.

  • Hello Mike:

    Anyone who has lived with a women who is pregnant will tell you at certain times they can become extra sensitive to certain external stimulus.

    Regarding dangers of having backyard pools (drowning or electrocution) was why we didn't have one built at our Florida residence.

    Peter Brooks

    Palm Bay Florida USA 

  • Hello Philip:

    There are situations in medical research where opposite sex bias exists - example is in hip fractures where periodic tests for Osteopenia (using Dexascan) is recommended for women but not for men. It isn't because men don't get hip fractures but because there is little published research with men. The ratio of women to men for hip fractures is estimated to be 80:20 .

    Peter Brooks

    Palm Bay Florida USA  

  • Hello Philip:

    As a follow on to my previous response:

    Men can also get and die from Breast Cancer!

    It happened to a guy who used to work with me.

    Peter Brooks

    Palm Bay Florida USA 

  • Men can also get and die from Breast Cancer!

    Roughly 1% of cases.

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