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Posted By Robert Randall
Here’s one for the “leckie’s” out there
I notice that the HSE recommend 12v or 24v ELV lighting when working inside steel tanks (INDG258). Why is 110-volt centre-tapped earth equipment not considered suitable? Is this because there is a greater risk due to the possibility of the cable coming into contact with the steel tank and chafing and thus energising the tank at 110-volts?
Don’t be offended but please only answer this question if you definitely know the answer, i.e. you are qualified in the appropriate discipline.
Regards, and thanks in advance,
Bob R
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Posted By Malcolm Chambers
The recommendation is there to reduce the possibility of electric shock to a minimum. 110V systems only produce 55V to earth, but this is still considered too high.
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Posted By Garry Homer
Working inside a steel tank is a 'special' location as defined by the wiring regulations. Section 606 in the 16th ed and 706 in the new 17th ed.
The concern is that a persons body can be in contact with a large surface of conducting material and there is very little that can be done to avoid it. Therefore the regulations require supplies to hand lamps to be SELV - Separated Extra Low Voltage. Reg 606-04-02 or Reg 706.410.3.10
The definition of Extra Low Voltage within the Regs is; normally not exceeding 50V ac either between conductors or to earth. Clearly the normal centre tapped 110V transformer does not meet this requirement.
Hope this clarifies why the HSE give the advice they do.
Regards
Garry Homer B.Sc. MIEEE and member of NAPIT
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Posted By Robert K Lewis
Garry
Correct me if I am wrong but I recollect a welder in a tank was electrocuted when egressing a tank and broke a 110volt bulb. It was about 8 years ago. But my memory plays tricks at times:-)
This would add emphasis as to the HSE logic.
Bob
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Posted By Robert Randall
Thanks Gary and Bob et al,
that was helpful.
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