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Torch - drawback


#1

Hello dear all, I purchased a little torch quite a while ago and I am
using propane and oxygen. So far, I am pleased with the torch. It’s
great to solder with, but the drawback is that I cannot use it to
melt sufficient amounts of casting grain. I need something else for
that, preferably as economical as possible. Could someone give me
some advice about this? Thank you for reading and with best regards,

Will


#2
     I purchased a little torch quite a while ago and I am using
propane and oxygen. So far, I am pleased with the torch. It's great
to solder with, but the drawback is that I cannot use it to melt
sufficient amounts of casting grain. I need something else for
that, preferably as economical as possible. Could someone give me
some advice about this? 

Will, I had exactly this same problem. My solution was to watch eBay
for a couple of months. I eventually got a slightly used Kerr
Auto-Electro Melt for less than half the list price - even came with
4 graphite crucibles. A dental lab was selling their backup unit.
It works fast, clean and cheap - I have never regretted it.

Jim Marotti
Lancaster, TN


#3

Economical torch for casting or making bars for rolling would be a
natural (city) gas boosted with oxygen. If you do not have natural
gas service, you can get methane (practically the same thing) in a
compressed gas cylinder. Still fairly cheap as fuel gas goes. In my
opinion, the best is hydrogen, but the cost is higher. Keep safety
rules and issue in mind along with $$, when it comes to fuel gases
and their use. Ask your welding gas supplier about the cost of
methane vs propane and the appropriate regulators, hoses, and the
torch itself. I suggest you avoid the very cheap acetylene. It can
be used but has its issues, being heavier than air like propane.


#4
I suggest you avoid the very cheap acetylene. It can be used but
has its issues, being heavier than air like propane. 

I believe that acetylene is lighter than air. That is why I chose
the PrestoLite for my basement studio.

Marilyn


#5
I purchased a little torch quite a while ago...  the drawback is
that I cannot use it to melt sufficient amounts of casting grain. 

Hi Will, There is a special tip for the Little Torch for melting
casting grain. It has a long neck with a cylindrical head, and
several pinholes to create a kind of “composite” flame, for lack of a
better term. Still has it’s limitations, but much better than trying
to use the #5 tip. Give it a try, if you haven’t already!

All the best,
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com


#6

Will, Do you have one of the multi-orifice tips for your little
torch? I have cast upwards of an ounce of sterling with my little
torch using propane and 02 but I use the casting tip which has 6
orifices and puts out a pretty good heat. Rio has them but they are
also available many other places where Smith products are sold. Cheers
from Don at The Charles Belle Studio in SOFL where simple elegance IS
fine jewelry! @coralnut1


#7
    I believe that acetylene is lighter than air. That is why I
chose the PrestoLite for my basement studio. 

G’day; The density of acetylene (ethyne) C2H2 is:- 0.6181 The density
of air at 20C is:- 1.2 + (depending on moisture present) (Handbook of
Physical and Chemical Constants) – Cheers for now,

John Burgess; @John_Burgess2 of Mapua, Nelson NZ


#8
        I suggest you avoid the very cheap acetylene. It can be
used but has its issues, being heavier than air like propane. I
believe that acetylene is lighter than air. That is why I chose the
PrestoLite for my basement studio.  Marilyn 

Marylin, I agree, I’ve always heard that acetylene is lighter than
air, and unlike propane, it will not pool in low areas of the studio
if there is a leak,


#9

Hi Will,

There is a special tip for the Little Torch for melting casting
grain. It has a long neck with a cylindrical head, and several
pinholes to create a kind of "composite" flame, for lack of a
better term.

The tip Dave is refering to is called a ‘bud’ tip. The btu (heat)
output f bud tips is much greater due to the larger number of
individual flames. Incidently, bud tips are available for torches of
all sizes, from the small jewelery torches to large industrial sizes
used in working with heavy steel.

Dave


#10
    I believe that acetylene is lighter than air. That is why I
chose the PrestoLite for my basement studio. 

Marilyn is right acetylene is lighter and does not pool in low
places like propane. For this reason propane is not allowed in ship
board spaces and acetylene is.

Jesse


#11

Los Angeles Fire Dept has banned acetylene and Propane in building
over 75 ft tall, expressly due to the heavier than air aspect of the
gas. Quoting an MSDS from
http://www.hoopersupply.com/msds/acetylene.htm I added the italics
and bold face to the font.

ACETYLENE IS EXTREMELY FLAMMABLE AND EXPLOSIVE. IT MAY DECOMPOSE
VIOLENTLY IN ITS FREE STATE UNDER PRESSURE IN EXCESS OF 15 PSIG. It
burns with an intensely hot flame. Potential explosion hazard exists
from reignition if fire is extinguished without shutting off
acetylene source. Ignites very easily due to low minimum ignition
energy; very wide flammable limits. Acetylene gas has an approximate
specific gravity of 1.0 and tends to stay in pockets rather than
dissipate.

Of course Hydrogen is far lighter than air, burns cleaner, about as
hot, and is just as available in most areas. It is also allowed in
tall buildings in Los Angeles for those who work platinum. Just my
opinion.


#12

Well, Daniel, the L. A. F. D. (and Hooper) are correct re propane,
as far as it being heavier than air, but wrong about acetylene . The
(correct!) specific gravity that John Burgess put up
clearly shows that acetylene is distinctly lighter than air.

On the other hand, I would agree with the LAFD in not wanting EITHER
in one of them in the tall buildings, due to the general fire
hazard. Perhaps they (or Hooper?) made a deliberate misstatement
about acetylene in order to help them make their point. Margaret


#13
Acetylene gas has an approximate   specific gravity of 1.0 and
tends to stay in pockets rather than dissipate. 

Daniel: I have researched numerous websites about acetylene and
there at least 18 that I read would indicate acetylene is lighter
than air. The simplest comes from HazMat

http://www.firehouse.com/training/hazmat/training/2001/12_vapor.html

and I copied part of the from that page for your
convenience:

Vapor Density Mnemonics

To aid in remembering which gases are lighter than air some
mnemonics or acronyms have been devised. A New York City fire officer
around the turn of the century developed a well-known mnemonic for
vapor densities. To train his fellow firefighters he used the term
"HA HA MICE" to remember the lighter than air gases. The letters
stand for;

H - Hydrogen
A - Ammonia
H - Helium
A - Acetylene

M - Methane
I - Illuminating Gases (old term for natural gas)
C - Carbon Monoxide
E - Ethylene

This acronym was useful for years but today we now know there are
more than eight gases that are lighter than (or the same weight as)
air. To remember the 13 gases that are lighter than air a new acronym
may be used as a mnemonic. The term “4H MEDIC ANNA” identifies the
lighter than air gases and they are;

Gas Molecular Formula AMU Vapor Density

H - Hydrogen H2 2 .07
H - Helium He 4 .14
H - Hydrogen Cyanide HCN 29  1.0
H - Hydrogen Fluoride  HF  10  .34

M - Methane  CH4  16  .55
E - Ethylene  C2H4  28  .96
D - Diborane  B2H6  27.7  .96
I - Illuminating Gases  CH4/C2H6  17.4  .6
C - Carbon Monoxide  CO  28  .96

A - Acetylene  C2H2  26  .9
N - Neon  Ne  10  .34
N - Nitrogen   N2  28  .96
A - Ammonia  NH3  17  .59

Note; Illuminating gases is “natural gas” which is a mixture of
approximately 90% methane and 10% ethane.

If you can remember this mnemonic for the lighter than air gases
everything else is heavier, including the vapors from flammable
liquids. In general terms, the heavier the vapor the lower it will
accumulate when released.

If you go to Google and put the question “Is Acetylene lighter than
air?” or “Is Acetylene heavier than air?” you will get a myriad of
sites to sift through (I read through 18 of them), all of which
indicate that Acetylene is lighter than air.

Kay


#14
  Acetylene gas has an approximate specific gravity of 1.0 and
tends to stay in pockets rather than dissipate. 

G’day; The above is quite untrue. My recent posting to
this forum had figures which were obtained from a world wide accepted
volume of definitive scientific That is: the density
of acetylene is 0.6181 whilst that of DRY air is 1.0 Thus acetylene
is lighter than air. I have no idea where the Los Angeles Fire
Department got that figure from, which was quoted. The density of
acetylene is easy to demonstrate. Simply fill a balloon with
acetylene, seal the opening and let it go. – Cheers for now,

John Burgess; @John_Burgess2 of Mapua, Nelson NZ


#15

To All Concerned, All of us are looking at various sources which may
or may not agree on all the properties. Lets separate the technical
definition of “Heavier Than Air” from “gathers in pockets” which
there is more agreement on, and is the real heart of a particular
explosion danger. I was surprised to be told that so many folks are
taught that it is lighter than air. I could very well be wrong, and I
am not going to try filling a balloon to see for myself. That’s a
great test under the right circumstance. Well, would that not present
a problem anyway, since “up” is where many electric lights are?
Miniscule sparks are common with electricity. I was taught by
various people over the years that acetylene, like propane is
heavier. That is a technicality in the face of the MSDS caution on
"gathers in pockets".

Acetylene has some other odd hazards like being so darn unstable if
pressure exceeds 14.7 or about 15 PSI. 40 PSI is routine with oxygen
and hydrogen, which is my favorite. Hydrogen gas also presents some
big explosion hazards in the event of a large leak or a lack of
anti-backflash equipment. Now, all compressed cylinders should be
kept upright, but it is far more critical with acetylene. Every fuel
gas has its particular behaviors. Acetylene seems to have more
hazards than most, and I really doubt that the density issue stands
alone in the rationale the LAFD uses to ban it in high rise
buildings. Everyone please remember that LAFD has this ban on high
rise (75ft and up) buildings only. We should also remember that LAFD
has a lot or real world experience with every explosive gas, and
limits public exposure more than a shop circumstance.

I also note the locations that I usually see acetylene being used-
Junk yards, muffler shops with their big roll up doors, and
ironworkers. All these locations enjoy great ventilation, two out of
three outdoors.

My opinion remains that if you can switch from acetylene to almost
anything else, do so. If you really like acetylene for some reason,
hopefully other than money, use it (or any gas) carefully. The money
spent melting precious metals is a small part of our costs. Of
course, opinions vary, I agree that many jewelers use acetylene quite
well.

From a safety standpoint, pick the gas with behaviors that most suit
your shop. We did. Open flame of every description calls for
ventilation far in excess of what you need compared to resistance
based electric melting, or on a better budget, induction. Natural gas
or methane is great for gold, silver and brass.

Daniel Ballard


#16
I also note the locations that I usually see acetylene being used-
Junk yards, muffler shops with their big roll up doors, and
ironworkers. All these locations enjoy great ventilation, two out
of three outdoors. 

But, I seem to recall that they use Acetylene/Oxygen torches to cut
parts, rather than the usual Acetylene/ambiant air mix that is used
by many silversmiths! Huge difference. The oxygen makes the mix so
much more explosive!


#17
the density of acetylene is 0.6181 whilst that of DRY air is 1.0
Thus acetylene is lighter than air".

John, sorry mate, …but for the first time in the many years
that I have been reading your posts, I have to disagree with you.

I do agree with you that acetylene is indeed lighter than air, I
,just don’t quite agree with your density comments. When quoting the
density of a gas, the temperature and pressure are quite important
as gas density is directly proportional to pressure and inversely
proportional to temperature. Meaning, that unless you know the
temperature and pressure at which the density was measured, it is
meaningless. Further, unless the air density you quote above is
measured at the same temperature and pressure as the acetylene
density, a comparison between the two is also basically meaningless.

The density of air at Standard Conditions (60F and 14.7 psia) is
0.0763 lb/ft3. The density of acetylene at standard conditions is
0.0686 lb/ft3 The density of propane at standard conditions is 0.1162
lb/ft3

A gas with a density greater than air (propane) will generally sink
to the ground in calm conditions. A gas with a density lighter than
air (acetylene) will generally rise in calm conditions.

A measure of the relative density of gases is called specific
gravity. Specific gravity is basically the ratio of the density of
a gas divided by the density of air. If the specific gravity of a
gas is greater than 1 it is heavier than air, if it is less than 1
it is lighter than air.

The specific gravity of air is 1 ie 0.0763/0.0763
The specific gravity of acetylene is 0.899 ie 0.0686/0.0763
The specific gravity of propane is 1.523 ie 0.1162/0.0763

Note that specific gravity can also be calculated by calculating the
ratio of molecular weights of the gasses. (My source for this data is
Gas Processors Association Engineering Data Book.

Now, after having spewed a bunch of technical mumbo jumbo, I believe
that most of the above is somewhat irrelevant. As I mentioned in my
post yesterday, whether a gas is lighter or heavier than air is not
the only consideration in determining its relative safety. All
combustible gasses (light or heavy) if allowed to accumulated in
enclosed and unventilated spaces ( like many home studios) have a
real good chance of exploding if they are exposed to an ignition
source.

Regards
Milt Fischbein
Calgary, Canada


#18

With regard to gass use in tall buildings… It seems to me that any
gas that was either heavier or lighter than air would be
hazardous… After all, one man’s floor is another man’s ceiling. If
a gas pools, whether below you or above you, it can explode. A gas
similar in density to air will tend to disperse more, and you’d need
a lot more to reach a danger level, right? And modern buildings are
very tight, generally, with unopenable windows. Just speculating–
–Noel


#19
Now, all compressed cylinders should be kept upright, but it is far
more critical with acetylene. 

Correct with acetylene, but not so with oxygen, air, CO2 or inert
gasses. Just consider scuba divers and firemen who use high pressure
tanks in all positions.

The basic problem with technical questions like this is that you
can’t believe many of the answers you get. Case in point is when I
recently wanted to replace the disposable oxygen tank on my Smith
Little Torch with a 50 cu ft high pressure cylinder. I had questions
about which regulator would deliver a steady low pressure and whether
I could lay the tank down horizontally to fit under my bench.

The first “expert” I asked was the counter man at the welding supply
company where I went to buy the tank. Answers were a little
suspicious, so I made a few calls and found someone I considered to
be a real expert.

Doug Perry is head of gas regulators tech support at Harris
Calorific. You can reach him at 800 447-6906 x179 He told me:

The inexpensive Harris Model 25 would provide steady low pressure for
the Smith torch. There was no need to go to a dual-stage unit like
their Model 425. He further pointed out that the regulator comes in
several different outlet pressure ranges, and suggested I be sure to
get one with the 0-15 or 0-50 range.

He said that acetylene tanks must be stored upright as there is
liquid in the tank. However, oxygen tanks may be stored and used in
any orientation.

He was also very helpful to explain proper procedures for changing
regulator fittings and for turn-on and shut-off sequences (Again I
had been getting conflicting advice from local “experts” on these
items also).

In my book it’s always best to go to the technical source for
questions involving personal safety. BTW, the regulator was only $52
from powertoolstore.com

  • Brad Smith

#20
    Now, all compressed cylinders should be kept upright, but it
is far more critical with acetylene. 

Correct with acetylene, but not so with oxygen, air, CO2 or inert
gasses. Just consider scuba divers and firemen who use high
pressure tanks in all positions.

I should have been more clear, I meant Jewelers in their shops, not
fighting fires, not scuba diving. In a shop a horizontal tank on the
floor subject the regulator to getting tripped over or stepped on. In
context please… Oh, and that was “should be” not "must be"
I’m Done with this topic