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Acetylene tank low despite reading on gauge?


#1

Hi there! I’m still working away on my first tank of acetylene
(single fuel torch) and noticed this morning that the flame, using my
#1 tip, sucks. When I switched to a #0 tip, the flame is okay, but I
feel like I’m running low on fuel (flame also is more orange than
normal, with the bigger tip and isn’t performing as it did before).
Yet, the regulator shows that I still have around 5 bars/75 psi left?
Is it time to exchange for a full tank

thanks
Ros


#2

Ros -

I have used mine below 50psi with good performance. What is your
line pressure? I find most people use it too low, that is, below
10psi. Turn up the line pressure (this advice is for a Smith
regulator, where you have two gauges, one for tank pressure and one
for hose line pressure) to about 12psi. Keep below 15psi.

75psi in the tank should still give you several more weeks’ worth of
use.

best regards,
Kelley Dragon


#3

Hello Ros,

I think you have a bad gauge or are reading it
incorrectly…acetylene should be run at less than 15PSI or it
becomes unstable…read as dangerous.

just an aside…do not lay the tanks down…not that you are, but you
may wish to at some point and you should not.

Acetylene comes out solution and gets drawn off the tank…the
interior is filled with a porous mass and acetone liquid in which
the acetylene is dissolved (like CO in a soda water bottle…change
the pressure and the gas comes out…bubbles).

I suggest you get the valve checked out.

Ric


#4

Ros, It sounds more like there is a blockage somewhere. For one
thing, I find the ‘gas’ only torches sometimes get a build up of soot
in the tips from incomplete combustion. Try this, take off the tip,
wrap the end with a piece of plastic or cellophane to keep you lips
off of the metal and blow gently through the output end. You will
find your breath will easily go back down through the tip whereas if
you try to blow from the input end, it will not.

Now try the tip again and see if it cleared. Let us know so we can
further analyze the problem.

Cheers from Don in SOFL.


#5
Is it time to exchange for a full tank 

I’d think it’s more likely time to clean that tip. Check that the
orifice isn’t clogged or dirty…

While the smaller tip needs less gas, it needs the same pressures to
work. If it works, there should be enough pressure and gas to work
with the larger tip too, so if the flame is bad with the larger tip,
the problem is likely with the tip, not the tank. In order for these
tips to work, there is an orifice that shoots a jet of fuel gas past
a vent opening in the side of the tip. That causes a venturi effect
that sucks in the needed atmospheric oxygen to properly mix with and
burn the fuel gas. If something blocks that proper working of that
orifice and venturi, then not enough air mixes with the gas, and you
get a yellow sooty flame, if any flame at all.

Peter


#6

Sounds more like your tip is dirty and may have a carbon build up
giving you the yellow flare. Get a commercial tip cleaner tool from
your welding supply shop.


#7

Check the filter on the tip… I’ve had the same issues with a
Prest-O-Lite before. I am using a Smith now, but I’d image all tips
have a filter. On the Prest-o-lite it is on the end that screws into
the torch handle… if I remember correctly it looks like a hex screw
with a mesh in the middle.

If you are only having problem with one tip… has to be the tip.
You can buy the filters at welding supplies stores or online.


#8

If you are using an acetylene torch, there should be a small screen
like filter in the part of the tip that screws into the handle.

These filters are used to keep the torch from getting plugged with
contaminates.

The filter itself can get plugged over time & prevent the torch tip
from working.

Most of the time, the filter is held in place by a snap ring. The
snap ring can usually be removed with a tweezers with a small tip.

If the filter is plugged, it can be removed & replaced. Replacement
filters are available from shops that sell welding supplies & fix
welding equipment.

Dave


#9

Ros

As I mentioned to you offline I’ve had the same experience as you so
after advice from somewhere (can’t remember where), I switched out my
tank and was back to normal operations. However, I read Kelly’s
comment:

I have used mine below 50psi with good performance. What is your
line pressure? I find most people use it too low, that is, below
10psi. Turn up the line pressure (this advice is for a Smith
regulator, where you have two gauges, one for tank pressure and
one for hose line pressure) to about 12psi. **Keep below 15psi.**

If you were taught, as I was, to never set the line pressure above
10psi, Kelly’s comment may indeed resolve the problem. My tank is
getting low so I’m going to try this when the flame starts
misbehaving.

Thanks Kelly! I learned something today. Based on my training I
thought it was unsafe to exceed 10psi with this regulator.

Iris


#10

Thanks everyone for the advice - I think that I will have several
days, if not weeks, left in my tank at 75 psi!! I looked sternly at
the larger tip and blew down it as hard as a I could (yes, I did
wait until it was cool - thanks to the orchid member for pointing
out that piece of important advice and for the intended giggle).
Then I shook it violently and peered down its tip (saw nothing, not
that I could) and examined the screen (also very helpful advice).
All is well for the moment, in my oven-like workshop :slight_smile: Again,
thanks so much everyone - I really don’t know what I’d do without
the advice provided on this forum!

Ros


#11
If you were taught, as I was, to never set the line pressure above
10psi, Kelly's comment may indeed resolve the problem. My tank is
getting low so I'm going to try this when the flame starts
misbehaving. Thanks Kelly! I learned something today. Based on my
training I thought it was unsafe to exceed 10psi with this
regulator. 

Two points: If you set the pressure too high for the tip you are
using, you won’t blow up your house, you’ll blow out your flame! If
you can’t get it to light, or you see a gap between the tip and the
flame, it is blowing too hard.

Second point: the reason the flame “misbehaves” when you get down to
the end is that you are burning the acetone the acetylene is
dissolved in. It simply will not burn as hot. Switch/refill the tank
and have done with it. More pressure will not fix it, more acetylene
will. You should rarely need more than 6-8psi on a normal soldering
torch.

Have fun!
Noel


#12

One reference that I have gives 15 psi as the pressure when
acetylene will explosively decompose. Another states:

"Acetylene is not especially toxic but when generated from
calcium carbide it can contain toxic impurities such as traces
of phosphine and arsine. It is also highly flammable (hence its
use in welding). Its singular hazard is associated with its
intrinsic instability, especially when it is pressurized. Samples
of concentrated or pure acetylene can easily react in an
addition-type reaction to form a number of products, typically
benzene and/or vinylacetylene. This reaction is exothermic.
Consequently, acetylene can explode with extreme violence if the
pressure of the gas exceeds about 200 kPa (29 psi) as a gas[16]
or when in liquid or solid form. It is therefore shipped and
stored dissolved in acetone or dimethylformamide(DMF), contained
in a metal cylinder with a porous filling ( Agamassan ), which
renders it safe to transport and use, given proper handling." 

If the material in the tank is a liquid, then the pressure gauge is
reading the vapor pressure (which can vary highly with changes in
temperature). Opposite to this is compressed gas, where you are
reading the actual gas pressure. Vapor pressure will always be the
same as long as some liquid is in the tank. Gas pressure will
decrease as the amount of gas decreases in the tank. Propane is also
a liquid. Oxygen is a gas in the tank.

Just be careful out there.

John
John Atwell Rasmussen, Ph.D., AJP


#13

Changing or cleaning the filter is also a way to keep things
flowing.

Marianne Hunter
hunter-studios.com