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Acetylene prestolite torch safety


#1

Hi all,

I have an air/acetylene prestolite torch in my home studio and am
familiar with the everyday actions needed to use it to make my
jewelry but am now feeling a little bit nervous and unknowledgeable
about the real fire and safety risks. I’ve taken many jewelry
classes but feel that I haven’t learned the nitty gritty about torch
systems. Any feedback and/or advice for the following questions
would be greatly appreciated.

  1. How toxic is the acetylene? I use the torch in a small room in my
    home. I open the window and sometimes use a fan but should I be
    doing more? Should I be wearing a respirator?

  2. How dangerous is it really to have this tank in my home? I am
    very cautious but obviously one can never know what’s going to
    happen. Would there be a huge explosion if there were to be a fire
    in my home? What would happen if the tank was dented?

I know I should have inquired about these things earlier and have
tried doing research online, etc. but I feel that the answers so far
have been very varied and vague. I wish that these topics were
discussed more in jewelry making classes. Any recommendations for
workshops, books, or websites with pertinent would also
be greatly appreciated.

Thank you!
Sara


#2

Sara,

Of all the tanks and gasses you could have picked, the acetylene is
likely the safest for use inside your home. There are a couple of
reasons for this (and why your homeowner’s policy and your local fire
inspector likely won’t have a problem with it, but you should check
anyway). First, acetylene is lighter than ambient air, so it floats
up and dissipates (unlike propane, which puddles and ponds at floor
level so it isn’t smelled until you have a REAL problem just before
it goes boom). As acetylene is floating up, you also can smell it,
which alerts you even earlier to the possibility of a leak.

Any compressed gas can cause a fire or explosion, so you need to be
cautious about caring for the cylinder. It should be strapped into a
welding caddy or firmly chained and secured to a non-moveable wall or
built-in object. This is so that you can’t knock it over and also so
that if it does somehow become punctured, it won’t fly all over the
studio and become a lethal missile.

When you are soldering, you’re not breathing acetylene or the
acetone in which it’s dissolved in the tank. Instead, you’re
breathing the residue from burning off the acetylene. You’re also
breathing the residue of your flux, dust or other contaminants from
your soldering block, etc. So good ventilation on the soldering table
is a MUST… it needs to be drawing off the fumes, ash, and residue
from the heating process and moving all that AWAY from your face and
outside. You can do this easily and cheaply through a high-CFM
exhaust fan (in an outside window) that is attached to a metal dryer
hose that you can position right by your work area. If you light a
candle in front of the intake, it should very clearly and
immediately draw ALL of the candle smoke into it.

Get a copy of Charles Lewton-Brain’s book on workshop safety as well
(http://www.lulu.com/content/1322094). Definitely worth the money!

I hope this helps!
Karen Goeller


#3

I would not characterize acetylene as “safest for use inside your
home” for a few reasons. Though acetylene will not pool in low areas
like propane or other liquified gases, it does have the widest range
of combustibility of any gas and takes the coolest spark to ignite.

Leaked acetylene will combust in any mixture in air from 2% to 80%
and a spark from static electricity (635F) is enough to ignite it. If
you smell leaked acetylene your next thought should be whether if you
touch something you are going to throw a static electricity spark and
start a fire!

By comparison propane and natural gas have a range of combustibility
of about 5%-15% and require a much hotter spark to ignite; propane
needs a 920F spark and natural gas needs a 1,163F spark. Natural gas
also has the advantage of being much lighter than air (specific
gravity of.6 compared to acetylene at.9 and propane at 1.5) so it too
rapidly dissipates.

The other danger is simply having a cylinder of fuel gas in your
home. Cylinders store a lot of energy in a small place. Consider that
a “B” tank of acetylene has 40 cf of gas or 58,800 BTUs of energy
while a 5 lb propane tank has 108,000 BTUs. To get a feel for this,
one BTU equals the energy from lighting one wooden kitchen match.
Think about that acetylene tank as having 58,800 matches or the
propane tank as having 108,000 matches and they danger that would
present if they were all lit at once.

In London, UK there is a safety campaign focused on acetylene
cylinders, which you can link to here:
http://www.london-fire.gov.uk/news/cylinders.asp#safe_cylinder

The website notes that from January - June, 2007 there were 17 major
acetylene incidents in the city that caused roads and buildings to
be shut down. The website notes:

“Acetylene presents a unique risk in comparison to all other bottled
gases due to its instability. Heating or mechanical shock can cause
spontaneous internal heating. The risk of explosion remains for 24
hours unlike all other gases which are safe once the initial fire has
been extinguished. In the past whole cylinders and fragments have
travelled for 175 metres.”

Heating can result from a torch flashback and “mechnical shock” can
be as simple as a cylinder falling over or being dropped. If this
happens it would be like lighting all 58,800 matches at once.

My company manufactures natural gas pressure boosters, systems that
eliminate gas cylinders from jewelers’ studios. Our customers
include jewelers in shopping malls, where gas cylinders are normally
prohibited and our systems are permitted in the downtown Los Angeles
Jewelry District where all gas cylinders are also prohibited. When a
Fire Marshal in Boulder, CO came upon one of our systems being used
by a glass lampworking artist his comment was, “This is a fireman’s
dream!”

I would argue that gas-to-gas natural gas is far safer than
acetylene, and using a torch booster as the gas supply is safer than
any gas in a cylinder.

Ed Howard
G-TEC Natural Gas Systems
www.safe-t-gas.com


#4

When I was learning metal work, my first teacher gave us a stern
lecture on the hazards of acetylene. “You can hit an acetylene tank
with a hammer… once.” Made a big impression on me. More recently
there was a story on the local news about a parked car that
exploded. They thought it was a bomb at first. Turned out the owner
had a freshly filled acetylene tank in the car. There was a leak in
the tank, and when he opened the car door, a spark from the interior
light ignited it.

I don’t want that in my house.

Janet Kofoed
http://users.rcn.com/kkofoed


#5

Firstly, I want to thank Mr. Howard for clarifying the issues
surrounding acetylene/natural /propane gas in a simple,
understandable way. I do have some questions for him for my
particular set up.

I wish I could achieve the perfect arrangement for my oxy/propane
Little Torch in my own studio. My situation is this, at the moment I
divide my time where I live (and work) between Maine and Illinois. I
have to pack up my tools and some equipment and move them every 6
months. In Illinois we heat with propane and have a huge tank in the
back yard. (ugly, but necessary) I am not sure about a convenient,
safe, economical way to tap into this tank to use for my torch. My
workspace is in the basement, though I don’t know if this has any
bearing on this. I have over the years simply used a propane tank
like the one you use for gas grills. I don’t, by the way, transport
my gas or oxy tanks. I have them at each site and leave them there.
I have used this arrangement for my tanks for years and have had no
problems. I am very safety conscious and follow recommended
precautions (ie: close down the regulators at the end of the work
day, bleed the lines, back off the t valve, use flash back
arrestors, strap tanks into place to avoid tipping), I feel
comfortable with my set up except for this particular issue of tanks
in the studio, which I feel limited in my ability to rectify.

In Maine, we use heating oil or kerosene as a heating source so I
don’t have a ready supply outside to tap into, not to mention not
having the money to get a larger stationary propane tank set up
outside. Would you suggest any alternatives to having a propane gas
tank in my studio? I can’t really come up with one. BTW, I don’t
rent so I can retro fit if I want, also I live in the country so I
am not surrounded by others at a close range (just in case there is
an explosion!) I feel I am taking a calculated risk and am
relatively safe but I also don’t want to be convincing myself of
this because it is what I WANT to believe! I think oxygen is much
more prone to explosion than gas and I don’t worry too much about
that, so… you may see my logic! :slight_smile: It may be flawed but to be
honest, this is the route my thinking has taken me!! Also, since it
is Maine it gets mighty cold there. Is this an issue at all with a
small tank outside? What about the lines from the outside? I assume
they would have to be copper? I also don’t want to use disposable
cannisters. They’re too expensive and wasteful.

Another issue is that eventually I will open a small store front
with my studio space there and am worrying about my torch being used
in this venue. This may be where I HAVE to use disposables:(I
apologize for rambling on a bit. Thanks for any suggestions in
advance.

Victoria


#6
My workspace is in the basement" 

LP (propane) has a very dangerous property when used in a basement /
lower area; it is heavier than air and will pool in a low area. I
would reccomend that a line be run from outside. Then an electric
valve installed outside above grade, which can be wired to a shut off
switch. That way there will be a minimum of gas left in the piping.
Your procedures still sound good also. Any LP supplier or liscensed
installer should be able to install this for you. Also this could be
tee’d off of your existing LP system.

As an example: I once saw a closet door which had been blown off by
a LP leak. What happened was that there was a new tank set in the
yard. The line was run underground and had a flare connection 20 or
30 feet form the “manufactured” house (trailer). The line continued
underground up to the regulator, which was installed on the inside
of the crawlspace. There was a leak at the flare union, it traveled
underground following the line into the crawlspace. The owner
attempted to lite the furnace and it blew the door off of the closet
and burned him. The line should have come out above the ground
before continuing into the crawlspace, that way the leak could have
been dissapated outside.

I hope this helps, like many of the things used in the jewelry
world; ignorance is one of the greatest dangers.

Dan Wellman

For reference, commercial / industrial gas “trains” rated by the UL
etc. often use what is known as “double Block and Bleed”. This is 2
electric gas shut off valves with a bleed valve which opens when the
others shut, bleeding off the section to the outside.


#7

I will share my response to Victoria’s kind comments with everyone.

If you don’t have natural gas it is possible to use other gases
safely - the key is recognizing the unique properties of each gas
which make it dangerous and using the gas in a manner that respects
those properties.

From your description it sounds like you follow normal safety
practices by bleeding lines, backing off the regulator key, etc.
but I would definitely get the propane tank out of the basement. If
you own the house then putting the tank outside and running a line
into the basement would be easy to do. While it may be inconvenient
to go outside and open the valve on the propane tank, you will be
safer if you do for two reasons.

First, while I work with natural gas cylinders in my business they
have the same type of fitting as a propane tank for connecting a
regulator, a CGA510 (CGA stands for Compressed Gas Association).
Often after connecting a regulator to a cylinder I use an electronic
sniffer to test for leaks

http://news.thomasnet.com/images/large/451/451518.jpg

and I am surprised, even after tightening the fitting to what I
think is really tight, to find that I have a small leak anyway. If
the cylinder is outdoors it doesn’t matter but indoors, it might. If
you are going to bring the cylinder indoors you should consider using
soapy water (mixture of liquid dish soap and water) to check the
fitting to make sure you aren’t leaking even after you think it is
tight.

Second, there is always the potential for a manufacturer’s defect in
the tank or valve on the tank. Sometimes I find leaks in the valve
stem and this could cause gas to escape into your basement. This kind
of leak would also be picked up with a sniffer or soapy water if you
splash some on the valve itself.

In either of these cases having the tank outdoors will prevent the
leak from becoming a problem. You noted that putting a propane tank
outdoors in cold weather reduces gas flow and this is true but the
amount of gas you need with your Little Torch is so “little” that it
will not affect you.

As for the details of connecting an outside propane tank to an
indoors torch I would ask the local fire marshal or town building
department if there are any codes which affect doing this - you want
to be sure whatever you do is legal. They may say a simple hole
through which you run a red hose is satisfactory or there may be
other requirements. Personally I would have a plumber install black
pipe through the building wall, just like I am sure you have inside
your Illinois home to connect the furnace, hot water heater, etc.,
with a separate shutoff ball valve. It would have strength and
rigidity and be safer than a flexible hose - again, ask what the
building code/fire code says.

Unfortunately I am not aware of a torch booster that works with
propane; G-TEC’s Torch Booster is only for natural gas. If there was
a propane booster you could simply boost gas pressure to 5 psi to
your torch from the propane tank that supplies all of your other gas
appliances. I assume you set your propane pressure to about 5 psi so
connecting directly to the building propane supply would probably
give a very weak flame, although there might be someone out there who
has tried this. If you do, you want to be triple sure you have a
flashback arrestor, not just a check valve, on the gas hose.

Oxygen itself is not explosive…it just makes everything else burn
really well! The larger danger with oxygen is having a cylinder fall
and break off the valve, which turns the cylinder into a missle. A
full oxygen cylinder is charged at about 2,200 psi and if that
pressure is suddenly released the cylinder will penetrate concrete
walls.

When you get to the point of opening a retail business you may find
that either your lease or insurance company prohibits you from having
a propane tank indoors. We sell many of our boosters to businesses in
this situation because our boosters are permitted in places where
cylinders are prohibited.

Philosphically speaking, accidents are accidents - 999 times out of
1,000 you follow the safety practices that let you work with any gas
but one day you may forget to bleed a line, close a valve, etc and an
accident occurs. Or, when you swapped your propane tank the last time
you could get that 1 in 1,000 cylinder that has a leak.

When that happens the characteristics of natural gas and one of my
Torch Boosters are more tolerant of error than other gases and
storage devices. But if your only choice is propane, keep the tank
outdoors, check for leaks time you use the torch and be diligent
about how you begin and end each day so you are woking safely within
the limits of the nature of propane.

Good luck!

Ed Howard
G-TEC Natural Gas Systems
www.safe-t-gas.com