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Electrocuted by rectifier


#1

I have a very real fear of being electrocuted whilst attempting to
electro etch & plate. Is there anyone out there that has any good
hard safety tips on operting a plating rectifier. I have read much
about the process and the emphasis is always on the safe use of
plating solutions and chemicals (cyanides/acids etc.) What about
electrocution? How many volts and amps does it take for one to be
seriously electrocuted. I very much want to attempt to electro etch
small pieces of silver using a plating rectifier and was hoping I
could do this with a small unit with a max variable output of
0-5amp/0-12v providing it was relatively safe to do so. If, God
forbid, I came into direct contact with this sort of current/voltage
do you think I would survive ???


#2

Suzi

I have a very real fear of being electrocuted whilst attempting to
electro etch & plate. 

:slight_smile:

I don’t think you will be electrocuted, but, the Naval safety manual
puts the lethal current through the body at 32V at 100 ma for male,
and 32v at 67ma for females, these values have to do with skin
resistance differences between the sexes. I can tell you from
personal experience, women will ‘feel’ current before I do, I have to
get a meter and test to find it. Again from personal observations,
women will ‘feel’ 12 volts, I can not. I have experienced electrical
shocks on many occasions and have failed to die on any of them even
though the voltage and current were significantly higher than that
sited in the Navy Manual, but that does not mean I seek them out.

Seeing as how you should be wearing rubber gloves ‘anyway’, just put
them on before touching anything you will be fine.

The chemicals ARE of more concern than the electricity. Just be
prudent, wear your gloves. One last thing, take off any rings or
metal adornments before playing with the power supply. 12V at 5Amps
is 60 watts, take a 60 watt light bulb wrap it around your finger and
plug it in for a minute, the thought will not be as harsh as the
reality. But, you shouldn’t be wearing rings with your gloves on
anyway, might poke a hole.

Terry


#3

If you were to hold both the leads on a plating rectifier, and turn
it all the way up to 12v - 5a, you might feel a slight tingle, or you
might not. Those squarish batteries that go in smoke detectors are
called 9 volt batteries, and one way to test them is to touch both
terminals to your tongue. A new battery will give quite the tingle,
and a funny taste, but no heart attacks. Now, since I don’t play
around with electricity, I have never actually held the leads as I
said - but plating is quite safe, electricity wise.


#4

Fear not, suzi! There is no way you can be electrocuted by 12 volts.
It’s against the law! Ohm’s law, to be more specific. :slight_smile:

Jerry in Kodiak


#5

Most all these units use pretty low currents and voltages. They are
DC (verses AC - direct current verses alternating current) thus the
rectifier. A car battery is 12 Volts DC, and from one you CAN get a
tingle, but to get a jolt, you have to store it (capacitor) and have
the discharge come from it, and you are not using any capacitors in
a etching/electroplating system. 12 volts DC (if that is the voltage
that your unit is putting out is pretty safe. Now if you get “hooked
into” the 120 volt AC line coming from the wall socket to the
rectifier, now you are talking something that for sure can give you
a good buzz, and in the right situation, be really potentially
harmful.

I would be much more worried about the off gassing of the chemicals
in the solutions than the power (but both need to be given their due
respect). Cynides and acids can be deadly, so use of a GOOD vapor
mask, lots of ventilation and care would be wise here. Like most
things, if you know what you are doing, it all can be safe, if you
don’t know what you are doing, it can be dangerous, this is true
with most things we do in our daily living, so DON’T get overly
worried, but get informed and educated. A bit of a Google on the wed
will go a long way in getting up to speed with you need
on the subjects.

John Dach


#6

Suzi,

As another aside, I was in the office machines business when I first
graduated from college. Doing repairs or adjustments with everything
live, we regularly “lit our teeth up” as we’d say (110 volts). We’re
still here.

Brian Corll
Vassar Gems


#7

Suzi,

Read this right here on Ganoksin:

Don’t forget to wear your rubbers. :wink:

Brian Corll
Vassar Gems


#8
but, the Naval safety manual puts the lethal current through the
body at 32V at 100 ma for male, and 32v at 67ma for females, 

4 Comments

1- the current, voltage and frequency and waveform of the
electricity (don’t assume a rectifier puts out pure DC unless it has
inductive or capacitive smoothing circuits) are all interdependent
and the change of any of them will vary the numbers, so there is no
absolute number to rely on

2- that is with intact skin which acts as an insulator. Poke a wire
strand trough the skin or break the skin by cutting yourself with a
sharp edge and the voltage drops.

3- ref the male being 100ma and the female being 67 ma That is
interesting, wonder why. The skin resistance would cause the voltage
needed to be higher not the amperage ( voltage = push or the ability
to go trough resistance Amperage (or Ma milliamp) is the amount that
travels trough the body) I wonder if it has more to do with the
physical size of the average woman’s heart versus the average size of
a mans heart, with the additional current (amperes) being needed to
disrupt the firing of the male heart just because of it’s size. If
this is indeed the case then a 120 pound male would be just as at
risk as a 120 pound female.

4- With any electrical equipment the best protection would be a GFI
(ground Fault Interrupter) Outlet with an isolation transformer and
the rectifier set plugged into that, since the main risk is not
electric current flow trough you between the negative and positive
pole of the rectifier, but the failure of the transformer or circuit
in the rectifier leading to full mains voltage via a ground fault on
the output.

To be honest Just a GFI in a non industrial setting would probably be
plenty, and quite frankly at the very low cost of GFI outlets today
to not use them where there is water around is asking for trouble.

Just my 2 cents worth
Kay


#9

Just speaking from experience: It depends a lot on conditions, but it
usually takes a few hundred volts to put enough amps through a
person to do them any real harm. Most people dont even get a tingle
from 12 volts, unless they do something strange like sticking the
wires in their mouth.


#10

Hi Suzi,

My wife Karen Bahr pointed out your concern to me. There seems to be
a lot of response to your query by people that are mostly correct but
conclusive knowledge is helpful when overcoming fear of any kind.

The voltage (Volts) is the force which drives the current (Amps)
through any circuit and the resistance of the circuit (Ohms) is what
opposes that current flow. If you don’t li+ke abstract thinking,
consider this system as equivalent to a water pump which pushes the
water flow through a restrictive size of pipe.

Only salt water is a conductor while plain water is only a
semiconductor with a much higher resistance. This is good to know
when trying to get an electric lawn mower with a wiring problem to
start, with sweaty hands. For lower voltages, like your 12 volt
application, a little resistance such as normal, dry skin resistance
is quite sufficient to oppose the flow or current to very safe levels
while you do your electrical plating or other processes.

Current pathway is absolutely necessary for electrocution to occur
regardless of voltage or the current it causes. This means the
current has to go through your heart during this situation, even on
line voltages to your home at the electrical panel. Your feet have to
be grounded very well through sweaty socks and poor shoes on a
somewhat conductive floor like damp concrete or your other hand has
to come into contact with the grounded panel housing or any water
pipe nearby which is also a ground connection. This situation has to
be in place while you deliberately touch a live 120 volt connection
in your electrical panel.

Lethal electrical shocks also have to happen when a person’s heart
is in the correct phase. If the shock occurs just when the heart is
changing state from closed to open or open to closed and if the
current is at 35 ma. or more (Thousandths of one amp.), then the
heart will likely go into fibrillation and a hospital with a
defibrillator is the only way or correcting this if time permits.

A person’s body is a bioelectrical unit which uses electrical pulses
from the brain to control muscles. When a person feels a slight
tingle from a shock, they are already around the 20 ma. range of
current flow. At 25 ma. the current is already high enough to start
overriding the control from the brain and causes the hand or other
muscles to clench tighter and letting go becomes less of an option.
The tighter grip lowers skin resistance and higher current occurs as
the danger increases.

Naturally, you sound like a person who is unlikely to be messing in
their electrical panel anyway but the info is good to know and may
allay some of your concerns about lower power capacities in various
applications.

Your variable current output up to 5 amps on your machine infers to
me your liquid process solution has to be quite conductive or that
low voltage would not be able to push anything near 5 amps through
that liquid. A comparison of safe voltages using a 9 volt battery is
not valid to me since that battery is current limited and likely
cannot deliver anything lethal under any conditions.

Because your process liquid sounds quite conductive, please use
rubber gloves during this part of your work and dry shoes if on
concrete floors. If the rubber gloves become wet inside with solution
and the current path is not good, I believe there is some risk and
suggest you change to dry gloves immediately.

As far as gas risk from the process, I agree that could be
substantial. Consider the path of the gas during this work and locate
your exhaust fan is the appropriate location to prevent breathing
anything harmful. I mounted Karen’s exhaust fan right in her bench as
apposed to any ceiling unit. This way any fumes or gases are
exhausted before they reach nose level.

I hope this info gives you a more comprehensive understanding of
electrical hazards and how to feel more comfortable around any kind
of power.

Regards,

Dan Bahr, Master Electrician Certification
Machineworx
Husband of Karen Bahr
Karen’s Artworx


#11

At the risk of adding to the ad nauseam response to this gal’s
question, I ask a question: Couldn’t you simply turn it off the power
supply before touching any electrical component?

asks steve, an industrial electrical/electronics/computer/automation
tech with some 30 yrs experience.