25 Aug
2015
25 Aug
'15
11:20 p.m.
Dec quad high boards had metal extractor handles which were possibly
attached to metal rails, and if the wiring was wrong, could deliver a shock.
Microdata card extractors were always engaged to a rail that was metal,
and in one site I was at, there was a CE sized hole in the wall behind a
system when the engineer extracted the printer card and the card
extractors came free from the system. Turned out there was a 120v
potential between the "dedicated" power for the computer and the printer
which was plugged into the normal building power.
There was probably as much as an amp going thru the grounds from the
terminals in the building and the ground of the system. Miracle that he
was not severely injured, and also that the system was working at all.
Turned out that the entire building which had been expanded over a
period of growth for the business of about 40 years had had power panels
installed with "outdoor" grounds at the time to main panels in various
places, and the grounds were all dropped to local earth. 10 different
grounds, with terminals connected and grounds coming back to the main
system.
But you always were well served to de-energize systems and pull the
power if you didn't want to be hit by this crap as there was no way to
be clear of this problem.
thanks
Jim
On 8/25/2015 10:41 PM, Jarratt RMA wrote:
As a child I remember getting a shock from a fridge
and being "thrown"
across the room into the wall opposite. I really did crash into the
wall quite hard, so I can imagine it being very easy for the shock to
cause other injuries.
Regards
Rob
On 26/08/2015, tony duell <ard at p850ug1.demon.co.uk> wrote:
Remember
that most injuries associated with electric shock are secondary -
that is, the real damage often occurs when the individual recoils from the
shock, jamming their hands into even worse places in the equipment - like
rotating assemblies. And then there's the innocent guy behind you, who
gets
knocked into his equipment, when you jump back.
An obvious example of this is the
the charge stored on the 'capacitor' of a
CRT
(the capacitor being formed by the final anode coating inside the glass
flare and
the coating on the outside) is not likely to be lethal for most people. But
it will
you jump, you will then either drop the CRT (if you are carrying it) or jerk
back
and break the CRT with whatever tool you are holding. And then the CRT
implodes, you get showered in glass....
-tony