Is propane safer than acetylene?

Peter,

Acetylene has a much higher rate of dissipation in air, so leaked
acetylene tends to quickly spread out within a given air space, and
it takes a good deal of initial leak before you reach an explosive
mix at all. 

Acetylene is definitely less dense than propane and in fact is close
to the density of air, but unless there is air movement in the
studio, caused by good ventilation, both acetylene and propane will
tend to hang around in that room as they really have no place to
dissipate to. True, the propane will want to accumulate near the
floor, but the rate of dissipation is really controlled by
ventilation rather than by a property of the propane or the acetylene
itself. Also, propane will not plummet to the floor instantly as if
it was a solid poured out of a bottle. It is a gas and will float
around the room with a tendency to pool on the floor but at any given
time there will be some concentration of propane on the floor, a
lower concentration of propane in the middle of the room and maybe an
even lower concentration of propane floating up around the ceiling. I
am about 5"10" tall. When there is a propane leak near the floor of a
room, I can always smell it standing up ie over 5 feet above the leak
near floor level.

My totally unverified intuition would be that the most dangerous
situations would be where there is already a pretty steady source
of ignition, and all that's needed is for the gas to reach the
lower level before things go boom. If it hasn't ignited yet at 10
percent, why would it somehow be more likely to ignite at 50
percent, for example. 

The more gas that has accumulated prior to being ignited, the bigger
the explosion. Therefore, having a source of ignition close to your
gas leak can actually be a good thing as the gas will reach the
ignition source prior to accumulating significantly in your studio
and flash off and potentially cause a fire rather than an explosion.
The worst explosions typically occur when a gas has been leaking for
a long time and does not find a source of ignition. So the gas sits
there and waits until you come into your studio and flip on a light
switch.

I can't say I'm all that concerned with the fact that acetylene
remains explosive through a higher concentration range than
propane. 

I have to disagree with you here. If you released an amount of
propane into a poorly ventilated room and an equal amount of
acetylene into another identical poorly ventilated room and then
provided each room with an ignition source, the room with the
acetylene will have a higher chance of experiencing an explosion
simply because it has much a higher explosive range.

Propane tanks, while also usually well made, are generally lower
priced, and mass marketed. That might suggest a greater chance of
manufacturing defects. Plus, they're engineered with an
overpressure release mechanism in the valve that can actually
intentionally let gas out if the tank gets warm. 

A propane BBQ tank should never ever be placed inside a home or a
studio, for the exact reason you describe. If they are overfilled at
the gas station, they will later overpressure as they warm up in the
studio and the relief valve will do what it is supposed to do, and
that is open up and release a substantial amount of propane into
your studio. The only propane tank I would ever bring indoors is the
small 1 pound disposable bottle. The relief valve on this bottle
will probably never open as the bottle is filled carefully under
controlled conditions. In addition, if the valve does open up, the
most it could ever release is the 1 pond of propane in the bottle.
Less leaked gas means less fuel means a smaller fire or explosion.

To avoid problems, you have to pay attention to your procedures,
the maintenance of your equipment and the tanks, and to making sure
you're working safely 

I agree with you completely on this point!

Regards
Milt Fischbein

Where is Natural Gas in all this? I hear propane and acetylene, but
not one mention of natural gas. It should be noted that Natural Gas
is a great alternative, especially for those that already have
Natural Gas available.

Electric soldering rarely reaches the broad dispersion of heat
needed to solder if it ever reaches temperature anyway.

Light soldering can be done with butane micro torches.

Todd Goodwin
Lapidarian Metalsmith

Cynthia,

I used Propane gas inside a 500sq foot Dental Laboratory for melting
alloy and soldering for nearly 12 years W/O incident, and with yearly
Fire Department checks. Check the local fire regulations for indoor
propane use under “portable tools”. Be sure to use the latest tested
tank in the smaller sizes, not the bar-b-que size. Check out the
closest Welding Supply for the correct regulator. Acetylene is much
dirtier when burning than the propane so I felt the atmosphere was
better.

Regards From Your Kentucky Friends,

Craig A. Pickett, RG CDT

Where is Natural Gas in all this? I hear propane and acetylene,
but not one mention of natural gas. It should be noted that Natural
Gas is a great alternative, especially for those that already have
Natural Gas available. 

Since the question was asked I’ll jump in from a G-TEC perspective!

Natural gas has many attractive attributes but like any fuel gas has
its own set of dangers if not handled properly. Natural gas is much
lighter than air (specific gravity is .6) so leaks rise and dissipate
easily, it has a narrow range of combustibility, can be used at any
pressure and is stable.

Of course, the right thing to do is make sure you don’t have leaks
and create a situation where these “attractive attributes” come into
play!

One unique situation with natural gas, however, is that most places
with natural gas have very low incoming pressure, often 1/4 psi,
making it it very difficult to use a UL Listed flashback
arrestor/checkvalve. Many jewelers connect their torches directly to
the natural gas line and this creates the danger of a flashback
exploding the gas meter. Regardless of whether you personally know
someone who blew up their gas meter, or not, flashback
arrestor/checkvalves are required by OSHA and the national model fire
code NFPA 51, which many governments simply adopt as their local
fire code.

A G-TEC Torch Booster elevates natural gas pressure sufficiently to
make the flashback arrestor/checkvalve work properly and give the
jeweler a good flame at the torch.

The other thing a Torch Booster does is eliminate stored gas. BTUs
(British Thermal Units) are the common denominator of measuring
energy value of different gases and you can think of 1 BTU = 1 wooden
kitchen matchstick.

With this perspective a 1 pound tank of propane equals 21,591
matches, a 5 pound propane tank would be almost 108,000 matches and a
BBQ tank is 431,820 matches. A 10 cubic foot acetylene cylinder is
like having a matchbox with 14,700 matches in it. A typical box has
250 kitchen matches so these numbers equate to between 58-1,700 boxes
stored in or near your studio.

But if you use natural gas and a Torch Booster you can improve
safety by eliminating stored gas and protecting your studio with a
flashback arrestor/checkvalve.

Ed Howard
G-TEC Natural Gas Systems

A G-TEC Torch Booster elevates natural gas pressure sufficiently
to make the flashback arrestor/checkvalve work properly and give
the jeweler a good flame at the torch. 

And what do these units cost?

My recollection is that the Revere Academy uses Mecos with natural
gas. Do they use a booster? Alan, are you reading?

Noel