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Propane (Again!)


#1

Hi everybody: Sorry to bring this up again but I really think it
is necessary. I have been using propane cylinders with oxy. for
soldering. As per everyones suggestions I have been keeping my
cylinder outside. I live in Newfoundland and yes it is still fairly
cool outside. Yesterday I retreived my cylinder from my deck, it
was around 14C. I left the cylinder upstairs while I had dinner.
It was around 18C indoors. In the middle of dinner the relief
valve on the tank went off. It scared the hell out of me.
Anyways, I took the tank outside and vented a little pressure. I
have used a 5lb tank for a few years and have never experienced
this problem before. I used to leave my tank in my shop before the
posts on Orchid, thankfully I did what was suggested. I hate to
think what could have been had I left the tank indoors & not been
home. Bye for now, Cary James


#2

I left the cylinder upstairs while I had dinner.
It was around 18C indoors. In the middle of dinner the relief
valve on the tank went off.

Strange. I currently use city gas, but I have used propane in the
past. On more than one occasion I have come into the shop to find a
fairly heavy smell of gas and an empty bottle. It has only
happened when the tank was nearly empty and I have often wondered
if the tank vented when the pressure dropped below a certain
point. Any ideas?

Bruce D. Holmgrain
e-mail: @Bruce_Holmgrain


phone:: 703-593-4652


#3
      On more than one occasion I have come into the shop to
find a fairly heavy smell of gas and an empty bottle. It has only
happened when the tank was nearly empty and I have often
wondered if the tank vented when the pressure dropped below a
certain point. Any ideas?..........

There was a thread about propane about a year ago that you should
be able to find in the archives but here is a recap of the facts.

The tank will not vent due to low pressure, only due to high
pressure.

In North America, the 20 lb propane bottles that we use on our
BBQs have a safety relief valve. THe valve will open anytime the
bottle is overpressured. The bottle will overpressure if it is
overfilled and then brought in from a colder area into a warmer
area. ie you get it filled on a cool morning and the gas station
guy overfills it and then the sun comes out and warms the tank.

If the relief valve opens outdoors, its no big deal, the propane
will generally dissipate harmlessly. The relief valve will close
after the pressure dissipates, in a few seconds to a minute or so.

If the relief valve opens indoors, like it did for Carey James

"the middle of dinner the relief valve on the tank went off. It
scared the hell out of me. "

the propane is trapped and there is a good chance of fire,
explosion and injury. Carey was lucky!!

The reason that the tanks have a relief valve is because if they
did not, then during an overpressure situation, the pressure would
continue to rise in the tank until the steel tank split open
releasing its entire contents.

What I have just described is true for propane tanks, but not
oxygen and acetelyene tanks, which do not have relief valves
because O2 and acetelyene behave differently from propane.

I would never bring a 20lb propane tank into my house!

Milt Fischbein


#4

Hello all. When I bought my Lil Torch, I chose oxy/propane in
disposable tanks for two reasons – the regulators cost less, and
the tanks are safer. Am I correct? That disposable tanks are
safer? I have flashback arrestors on both tanks. I realize that
these are an environmental drag, so much waste, but considering my
space considerations they work for me. Thanks.

Elaine
Chicago, Illinois, US
Midwest
Great Lakes


#5

What I have just described is true for propane tanks, but not
oxygen and acetelyene tanks, which do not have relief valves
because O2 and acetelyene behave differently from propane.
I would never bring a 20lb propane tank into my house!

All pressurized gas cylinders have over pressure vent valves
including oxygen and acetylene otherwise they are bombs . Look for
the little hex shaped cap with the holes in it on the opposite side
from the threaded receptacle where your regulator screws into the
valve body that is the relief valve.

Jim


@jbin
James Binnion Metal Arts
2916 Chapman St
Oakland, CA 94601
510-436-3552


#6

Hello Elane:

Do you have access to natural gas in your shop? I’ve used it with
oxy. for years and find it to be preferable to any other. Besides,
it’s one less tank to worry about.


#7

Good Advice about not bringing a filled propane tank into the
house OR GARAGE. We had a hot water heater start a small fire with
a BBQ propane tank in the garage. Needless to say, the blast took
1/3 of the house, burned the roof and rest of the house. If
propane is to be used in your shop, let the tank vent outside and
try to make sure the outside air and the air in your shop is
approximately the same.


#8

Milt F. (thats me) wrote…

      "What I have just described is true for propane tanks, but
not oxygen and acetelyene tanks, which do not have relief valves
because O2 and acetelyene behave differently from propane. I
would never bring a 20lb propane tank into my house!"............

And then James Binnion responded …

     "All pressurized gas cylinders have over pressure vent
valves including oxygen and acetylene otherwise they are bombs . 
Look for the little hex shaped cap with the holes in it on the
opposite side from the  threaded receptacle where your regulator
screws into the valve body that is the relief
valve."................

This is a bit of a dry topic, but I feel that it is worthwhile
setting the record straight for those who can hang in there long
enough to read it.

Both of the above are correct. All pressurized gas tanks have some
sort of pressure relief built into them. That is the law in North
America and hopefully the rest of the world. Propane tanks have a
spring loaded relief valve that pops open at a certain high
pressure and then snaps shut when the pressure in the tank drops to
a safe level.

Oxygen and acetylene tanks DO NOT have spring loaded relief
valves. They do however have pressure relieving devices that do not
reclose once they are open. This means that once they open, the
entire contents of the tank is released.

Oxygen tanks have a device known as a rupture disk (also called
burst disk or frangible disk). When an oxygen tank exceeds a
certain safe pressure, the rupture disk ruptures and allows all of
the oxygen to escape. It does not reclose and has to be replaced by
a qualified person. An oxygen tank will generally only overpressure
if it is exposed to extreme heat, such as a large fire. Leaving it
out in the sun can not cause an overpressure as with propane.

Acetylene tanks are equipped with a different device called a
fusible plug. This is a plug that is set into a threaded hole in
the tank. The plug is designed to melt when exposed to high heat
from a fire. The plugs melt at somewhere between 205 to 240 F
depending on teh age and style of the tank. Once the plug melts it
does not reseal, therefore the entire contents of the tank are
emptied.

You might wonder if its a good idea to empty an entire acetylene
tank into a fire. The bottom line is that it is better to feed the
fire than to have the tank explode and the pieces fly hundreds of
feet.

The reason that different tanks have different relief devices is a
function of the properties of the gasses that are stored in these
tanks. (by the way I am referring to B tanks, and other typical
welding/soldering sized tanks)

Propane is mostly liquid at its storage conditions, and vapourizes
as it is drawn from its storage tank

Oxygen is a gas at 2200 pounds pressure

Acetylene is unstable and likes to explode under pressure, so it
is actually dissolved in acetone and comes out of the acetone
solution as you use it.

Most of these devices are similar to oressure relief devices that
are found in a typical refinery or chemical plant (which I design
for a living when I am not in my basement crafting jewellery)

Hope that some of you got to the end of this and found it
worhtwhile.

Milt Fischbein


#9

Thanks Milt for your very understandable explanation of the
differences in the various gas tanks. Now that I understand how
they all work I feel safer with my propane and oxygen tanks. I
think they are safer in my shop which has a fairly uniform temp.
than outside or in an unheated garage. Jan, in southeastern Oregon
where it will probably snow tonite, even though the trees are in
full bloom.


#10

Thanks, Milt, I got to the end and will save your fine
descriptions of the different types of relief valves etc for
future. I know one day one of my students will ask about the
differences and now, I’ll be ready.

Nancy
ICQ # 9472643
Bacliff, Texas Gulf Coast USA


#11

Natural gas/oxygen is my fuel of choice. It is clean, cheap and
hot, although due to the low line pressure of city-supplied natural
gas, it does not produce enough heat to melt more than an ounce or
maybe two of metal.

It is a snap to hook up, but you should be sure the line is tight
by periodically testing it with a soapy water spray.

Second choice is propane/oxygen, a bit hotter, more costly, and
you need another tank and regulator.

Last choice is acetylene/air or acetylene/oxygen. The first is
difficult to adjust the flame, the second is far too hot for most
work, although I have a good friend, a great goldsmith, who swears
by it. Acetylene is dirty and full of carbon. -Alan Revere


#12

Milt

A question. If the propane tank is filled to spec and not over
filled will its relief valve open in normal environmental
conditions, i.e. sunny days outside or normal household temps? I
would find it rather dangerous to design a pressure relief system
that would open under the normally experienced environmental
conditions and would expect that this would be a violation of good
design practices and CGA specs.

Jim


@jbin
James Binnion Metal Arts
2916 Chapman St
Oakland, CA 94601
510-436-3552


#13

Hello Elaine, I must agree with Steve. I have used natural gas for
20 or more years,have just installed it in my new shop,and almost
all the professional jewelry companys that I have worked for have
used natural gas. My new employer here in Ca does use a second
propane torch just for casting and now I am wondering if I should
add it also just for casting. Any comments out there about propane
and castings? PS please tell Jan Cassel that I just got back from
a short lecture with Charles Lewton-Brain on Benchtricks. I can
understand why she wanted him to come to Chicago for cold forming
workshop! Great stuff! We all enjoyed the lecture tremendiously!


#14

hi, i am thinking of adding scapolite to my inventory i have the
GIA book but i am unsuer of the prices could someone let me know
the wholesale and retail price for scapolite and if there is any
demand for it.

thanks,
joe


#15
     A question.  If the propane tank is filled to spec and not
over filled will its relief valve open in normal environmental
conditions, i.e. sunny days outside or normal household
temps?......			

If everything went exactly per design, the relief valve would not
open, since the design of the propane tank, relief valve and the
80% fill rule are intended to prevent relief valve opening, except
under abnormal conditions.

Two conditions would have to be satisfied for the relief valve to
open

  • the tank is overfilled on a cold day
  • the tank is moved to a much warmer location and its contents
    allowed to warm up and expand.

In Canada, 20 pound propane tanks are typically filled at a gas
station by someone who has taken a short training course. The
propane tank is filled by weight on a large scale with questionable
accuracy. I would think that overfill in this situation could
happen fairly regularly.

In Calgary, where I live, temperatures fluctuate wildly in one
day. It is very common to wake up in the morning in the early
summer to 5C temperatures and and see 25 C by late afternoon.

Given the above, I would think that it is not uncommon for propane
tanks to releve quite often.

But as I said at the top of this note, if everything was done
correctly, ie tank not overfilled, no temperature change and a
reliable relief valve, the valve would likely not open.

My 20# propane tank never comes into my house. It is always stored
outside attached to my gas BBQ. I don’t use propane as a
soldering gas.

Milt


#16

Alan, The “gas” question has had so very many replies it is hard to
figure out what to do for ones home (garage) work-shop and also be
safe.

I asked locally after reading the online replies. It was suggested
that compressed air rather than oxygen would be better combined
with propane. I do not recall seeing compresed air mentioned.

Is tapping the house gas line something that has to be approved by
the gas co? In my garage there is both gas washer & dryer and
water heater. Is it safe to have the propane in there too? If not,
is it safe to keep it outside in a shady area?

Boy how I wish the White Knight, or The Good Fairy would get my
shop up and working.

Thanks,
Teresa


#17

Sorry to bring up this up again, but I’ve ben away. I have propane
and oxygen set up. What is the problem using it in an unheated
garage. If this is covered in the Orchid Digest can someone tell
where to look gfdor it or can Milt please explain it to me off the
list so as not to clog things up. Thanks to you all…as always.

Janet in Philly


#18

The last time this thread came up … or was it the time before
that … or the time before?? … I was the one asking questions
(and still do)! I remain afraid of keeping propane in my house
because of some of these same issues. Consequently, on the advice
of several on this list, I went ahead and sprang for the money and
located my tank outside, piping it in correctly. I even had a
permit from the local building code office. As a result, I feel
safer, and my insurance did not go up! It cost me about $150 US
to have about 23-feet of three-fourth-inch pipe installed and
pressure tested. This included all materials, over an hour
drilling through my foundation, the cost of the builder’s permit,
and a second visit from the gas plumber to remove his pressure
testing device. Not only do I think my piece of mind is worth the
trouble and the expense, but the rate increase estimate from the
insurance company was considerably more than $150 … and that
would have been PER YEAR! I would encourage anyone installing
flammible gasses in their home or shop to find out what the
building codes require, and do it! Even if it means hiring a
master plumber, as I did. And I’m usually one inclined to cut
corners!

Good luck all, and keep it safe!!!

PS Thanks, Milt!
Marrin Fleet
@Marrin_and_Mary_Dell
Memphis, Tennessee, USA
(About halfway between the Gulf of Mexico
and Canada, on the Mississippi River;
home of Elvis and W.C.Handy)