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Dust and static electricity explosions


#1

I have a question concerning explosions. This question comes to mind
after the sugar refinery explosion in Savannah. My daughter is a food
scientist at that plant. She tells me that anytime you have dust,
static electricity, and the right oxygen conditions an explosion can
occur. She says that nowhere in the plant do they have any vacuumed
systems, because it can cause static electricity leading to an
explosion. In their case, sugar is highly combustible. What I am
wondering is…has anyone ever heard of a polishing machine involved
in an explosion? Of course they are highly susceptible to fires due
to build up. But what about explosions? I am just totally freaked out
that sugar can blow up a huge factory badly burning over 30 people
and killing 8. Some still not recovered. If this had occurred just
two hours earlier, my daughter would be in that pile of rubble. Her
office was right beside the cylo that exploded. So with this heavy on
my mind, I am asking that we discuss the hazards in our workplaces.
We are all so busy, maybe we are not paying attention to things we
should be. Please, lets all give this some thought.

LaVerne


#2

hello,

I understand your concerns but I doubt that such an expolsion would
happen in a jewellery workshop. First, the dust we usually produce is
fairly thick and heavy, I think that for the dust to explode, it
should be “pulverised” in the air ( in cylos, dust is so fine that it
looks like smoke), for such a fine dust, I see only investment
plaster (which I do not use because I don’t do castings).

Discussing such hazards is a good idea.

Because I have students (only one at a time) in my workshop, safety
is important for me. I keep various dust/fume masks, gloves, aprons
and goggles there. I also ask them to wear trousers and no sandals.
The first lesson is always a workshop tour with an introduction to
the tools and their safety rules. I warn them not to catch any
falling object for it could be hot or sharp or both. Besides, I send
them on a break every two hours or so keep there concentration level.

Appart from cuts and burns or acid spills, I think the main hazard
of our trade is what we cannot see or smell like lead or cadnium slow
intoxication Acid fume and unsufficient ventilation in an issue, or
the reaction between acids and patina or plating solutions if one
forgets the baking soda step… I was told that it creates
mustard-gas!

Personnaly, I keep a window open most of the time and leave it open
overnight when I go home, I regularly check on my torch and clean it
every now and then.

As I enamel, dust is my enemy so keep the place as clean as possible
and work with wet abrasives.

I clean the all workshop at least once a week, my pickle is set on
the minimum temperature to avoid fumes and has a lid and I preferably
use leadfree enamels and cadniumfree solders. Recently (thanks to
Orchid) I found tarfree pitch. All my bottles and jars are correctly
labelled. Besides, I keep food ansd drinks on the opposite side of my
workplace, by my drawing desk and wash my cup and plate always
separatly with a dedicated sponge (I do not allow the students to eat
in the workshop, that’s only for me).

I don’t really think about all my safety rules it all is in my
habits now but I noticed that I am always exhausted after a lesson
with a beginner because I have to be extra-vigilant.

Juliette Arda
Artiste-Bijoutiere
Aix en Provence, France


#3

When I was in High School, my Physical Science teacher did a
demonstration with a metal paint can into which he put a candle next
to a little coffee stirring spoon attached to a rubber hose with a
squeeze bulb. The tube was aimed so as to puff powder from the spoon
into the area above the flame when the bulb was squeezed. He filled
the spoon with about one gram of powder of any number of different
materials, iron filings, wheat germ, flour, very fine sand, etc, and
then put the cover on the can, tapping it with a mallet to make it
really tight. We students tried burning the materials before the
experiment to determine their reactive qualities and then made
predictions about which powders would react, and which ones wouldn’t.
With every single type of material, when he squeezed the bulb, the
powder exploded with enough force to blow the top of the can up to
the ceiling. Even talcum powder and concrete dust. Made a believer
out of me.

Many a grain silo in the farm belt of the US has exploded due to
dust, as have many different kinds of factories. The type of dust or
powder is almost completely unimportant, only that it is fine enough,
suspended within a closed area in the right ratio of particles to
air, and there is an ignition source.

I worry about this enough to make it absolute non-negotiable policy
in my shop, that no one grind on steel or any material that causes
sparks at the polisher. One spark down the dust collector not only
can cause a fire, but also could cause an explosion of awesome,
potentially deadly force. Although this is not a likely scenario and
one I’ve never heard of actually happening, it is definitely a real
possibility with very serious consequences. After my experience in
Freshman Physical Science class, I take the possibility of an
explosion in a dust collector (or any other dusty environment) very
seriously.

I’m glad your daughter wasn’t hurt and my thoughts and prayers go
out to those who were not so fortunate.

Dave


#4

LaVerne, You are so right about protecting ourselves and our
employees from any possible hazards. Nearly all accidents are
preventable.

I grew up in the upper midwest, and every so often there would be
news of a grain elevator blowing up, just like the sugar plant. I
seem to remember that it was indeed the dust that was blamed, but I
think it may be just dust of an organic nature that would be
combustible. It will be interesting to hear of others’ input.

Thank heavens your daughter was not in the wrong place at the wrong
time.


#5
has anyone ever heard of a polishing machine involved in an
explosion? Of course they are highly susceptible to fires due to
build up. 

Richard, in order for there to be an explosion, the dust must be
flammable. The typical dust in a polisher is non-flammable - it’s
basically dirt. I have seen a polisher fire before, and it was the
bits of cotton buff and the like that were on fire. Plus it was a
very small fire, and I believe someone dropped a piece and it broke
the light bulb, which started it. It could be that someone might use
the machine with wheat powder or whatever for their own reasons,
which would be different. But tripoli and rouge - no.

http://www.donivanandmaggiora.com


#6

Since you are close emotionally to this incident Goggle search “dust
explosion abatement”

It is a well known problem. The first question to ask in these events
is not why but “why not before?”

There have been suppression systems available for over 25 years.
Generally it would not be a problem in a small workshop ( a dust
filled space can explode) but you should practice dust control for
lung protection. Dust collection systems can pop inside these
systems which are usually controlled by grounding and all metal
systems. Systems using plastic pipe are not highly recommended but
grounding is effected by running a exposed ground wire inside the
pipe.

jesse


#7
I am just totally freaked out that sugar can blow up a huge factory
badly burning over 30 people and killing 8. 

People don’t think of sugar as being flammable. But for the human
body, sugar is our gasoline. it’s energy storage ability is quite
respectable, and we can burn it for energy in our cells because it’s
a relatively reactive chemical. This is also why those of us with
diabetes have a problem with high blood sugar. it’s very reactive
stuff, and normally the body tries to keep levels of sugar floating
around to the minimum needed to keep the body fueled. More than
that, and the stuff causes serious damage.

With that background in the biochemistry of the stuff, it becomes
less a surprise that it’s not quite the same simple chemical it
seems. Now, it’s not so easy to ignite as gasoline, and catching fire
isn’t usually a problem when it’s in it’s normally seen form. But a
dry dust? Might as well have a nice mix of acetylene and oxygen
floating around.

the stuff in your polishing machine, however, is not in that
catagory. The flammable part is mostly the cotton fluff from the
buffs, and that part is indeed potentially flammable. The rest is
pretty heavy grease or wax binders, which while potentially
flammable, isn’t a dust, but rather caked onto stuff. harder to
ignite. And it’s full of the polishing compounds themselves, which
are generally oxides or silicates already, and not flammable. Try
lighting a match to a small pile of the stuff, and you’ll find that
while it can burn some, it’s hardly an aggressively flammable
material. And since it quickly settles out of the air, not forming an
airborne dust cloud, the risk is usually minimal, especially since
buffing doesn’t generally lead to an ignition source for the stuff.

One related thing to watch out for, however, is grinders and
grinding wheels, especially if used with steels or titanium. Sparks
flying off the wheel are white hot, and if they hit a pile of the
grindings already produced, THAT can flare into a fire surprisingly
well. Similarly, mounting grinding wheels in your polishing machine
and sending hot sparks into the dust collectors is probably not a
bright idea. it’s one thing to say the polishing waste is not easily
ignited (such as with a static spark), but asking it to not light up
when spraying white hot burning steel sparks into it, well, that’s
another thing altogether.

Peter


#8

Hi LaVerne,

The short answer is no. However, in an industrial context,
‘explosions’ of polishing dust were quite common around here. Let me
explain… Ordinary polishing ‘dust’ is not explosive as it is
basically non-flammable, how ever, in industrial situations of the
type we had around here at the height of the cutlery in dustry, every
factory had large ‘cyclone’ dust extractors which sucked all the
polishing ‘dust’ out into large circular bins hung on the outside of
the factory wall. As the polishing debris contained lint and fibres
which wore off the wheels and, in some factories, the cyclones also
took the dust from grinding operations (a silly combination but it
saved installing extra systems where the two operations were carried
out alongside each other on the same bench), sparks from the latter
sometimes set the cyclone bins on fire. As the polishing dust was
basically coated in heavy grease, these fires usually only
smouldered, making quite a bit of smoke but little flame - until the
enthusiastic fire crew arrived to extinguish them! Why they never
seemed to learn I will never know, but several times I have seen a
fireman sent up his ladder to take the lid off the cyclone bin and
squirt water into it. Of course, as soon as the lid was lifted, the
dust inside was disturbed and sucked upwards and this, combined with
the sudden inrush of fresh oxygen, made the bin flare up with a
whoosh in a most spectacular manner, often taking the fireman by
surprise and occasionally leading to burn injuries. So, in normal
cases where only a small amount of polishing is being done and there
is no mass storage of polishing ‘dust’, the chance of an explosion or
even a fire, are minimal.

Best wishes,

Ian
Ian W. Wright
Sheffield UK


#9

Laverne,

The key to dust explosions is that the dust is combustible to some
degree. This hazard is well known in coal mines, also grain
elevators and flour mills. (For example, grain scoops are made of
plastic rather than metal to reduce the likelihood of sparks that
might ignite dust stirred up while handling bulk grain.)

Since polishing dust is not combustible, hazards likely to be
present in a metalsmith’s studio will probably be of some nature
other than explosive dusts. Quite a few of these have already been
discussed at length in this forum. Examples hat come to mind are fuel
gases and oxygen used in torches, use of flashback arrestors and
checkvalves, use of dust collectors, ventilation systems and hoods to
minimize exposure to toxic fumes emitetd during soldering operations
or pickling, safety precautions for handling chemicals, safety around
polishng machinery, to name a few. You might check Orchid archives
for these threads, many of which are quite thorough in their
treatment of their respective subjects.

Dick Davies


#10
in order for there to be an explosion, the dust must be flammable.
The typical dust in a polisher is non-flammable - it's basically
dirt. 

Sorry John, but it doesn’t have to be flammable just react with
oxygen. Metals dusts cement powder and other “non flammable” powders
can explode but flammable ones are easier to ignite. That said the
likelihood of an explosion in a polishing machine is remote because
the dust is not dispersed in the air but sucked onto the filter
surfaces. A fire however is definitely a real possibility this is
why you should never grind ferrous metal in polishing motor with a
dust collector that is used for buffing as the cloth fibers and
grease from the polishing compound bars in the filter will burn with
a vengeance if the spark manages to ignite them while the fan is on

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#11

Thank you to everyone who responded to my question about dust and
explosion. The lesson I learned from the sugar plant explosion is,
just because it has never blown up before doesn’t mean it can’t. We
should never be completely comfortable that nothing can happen in
our workplaces.

Take Care
LaVerne