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Lighting the Meco Midget Torch


#1

While we’re talking about lighting torches…

I recently bought a Meco Midget to use with propane and oxy. It does
a good job, but I have some problems. I have to open the pressure on
the tanks to the absolute minimum possible, and likewise the torch,
to be able to light it. Then, the pressure of the propane gradually
creeps up, enlarging the flame and requiring that I turn it down
(hard to do without turning it off) or add oxy.

Now, obviously this is not what is supposed to happen, but I don’t
know which part of the system is likely to be at fault. Can anyone
help?

Many thanks!
Noel


#2
   Now, obviously this is not what is supposed to happen, but I
don't know which part of the system is likely to be at fault. Can
anyone help? 

The first thought is that you may be trying to use a tip that’s not
as compatible with natural gas/propane as it should be. some of the
very small orifice tips can be harder to light. but the standard NG
tips shouldn’t do this. They’re characterized by a central main
orifice in the tip, surrounded by several smaller “preheat” slits.

But your varying pressure sounds to me like a regulator that’s not
working right.

Also, I’d wonder just what these minimum pressures actually are. If
you’re using regulators intended for higher volume use, perhaps the
appropriate pressures for the midget are just at the very low end of
your regulators. Many regulators, especially single stage ones, will
have some trouble being stable at the very low end of their range.

I’d guess that with most tips, you’ll want oxy pressures of maybe 10
psi, or a bit more for larger tips, and gas pressures of 6-10 psi to
start with. So if your regulators want to just start off
deliverying 15 psi at their lowest setting, then you’ll have troubles
such as you describe.

Peter


#3

Hi, Peter, Thanks for your suggestions about my Meco. The regulators
are the ones supplied by Frei and Borrel with the torch, likewise
the tips, specified for propane. I guess I should call them. The
tips have one hole, and I’ve used only the smallest one, as the
flame is very hot. But, yes, I am using the lowest possible
pressure. I set it to 5 psi at first, and the pressure was so great
that I got a HUGE flame, plus the gas came out so fast that it would
accumulate in the few seconds it took me to light it (right in front
of my strong vent) that I’d get a momentary fireball! At first, I
chalked it up to never having used a Meco with propane, though I
used NG at Revere. But, clearly, this is a little nuts! The next step
needs to be to talk to the folks I bought it from, I reckon. – Noel


#4

Noel,

You need to set the the Oxy to almost 1psi. There is a
significantly longer flame than the mini torch, and it is HOT. I
had the same thing happen to me when setting the oxy to 5. Nearly
burned my hubby’s eyebrows off!

-k


#5
    I set it to 5 psi at first, and the pressure was so great that
I got a HUGE flame, plus the gas came out so fast that it would
accumulate in the few seconds it took me to light it (right in
front of my strong vent) that I'd get a momentary fireball! 

Sounds like you’re opening the valve too far to begin with. Just
barely crack it open. With natural gas or propane, you’ll have quite
enough gas to light, well before you can actually hear any hiss from
the gas flow. And when you light the torch, hold your spark lighter
at an angle to the torch tip, not right in front capping it. A
little bit of a fire ball isn’t unusual, but it shouldn’t be so much
that your singeing your hand or face or anything.

Peter


#6

Hi Noel and All,

I have a Meco Midget torch also so I just tried a little
experimentation. I have refillable oxygen and propane tanks with
Smith Equipment regulators. I normally use a Meco NG #0 torch tip.
My oxygen regulator goes up to 150 psi in 5 psi increments and the
propane regulator goes up to 60 psi in 2.5 psi increments. I
normally have both pressures set at about 15-20 psi when working and
the only problem I have had with this is that the valves on the
torch are open so slightly that it can be a little touchy setting
the flame the way I want it but I haven’t had a problem lighting the
torch. I pretty much arrived at these pressures somewhat
arbitrarily but had not done much experimentation since this has
been working for me. The procedure I follow when lighting the torch
is to open the tank valves, set the regulator pressures, turn on the
propane at the torch and light it with a striker. After it is lit,
I then add the oxygen and adjust both oxy and propane until I get
the flame I want. I do have to be careful that I don’t let too much
fuel gas out before I get it ignited with the striker or I too can
end up with a fireball. I have found that this is just a matter of
getting a feel for how much to open the torch valve to get
sufficient gas flowing to ignite and not so much to blow itself out
or create a fireball if the first couple of strikes don’t ignite it.

I just tried the same procedure but with both gas pressures set to
about 5 psi. I had no problems lighting the torch. Actually it was
easier than at the pressures I have been using because I have better
control with the torch valves. The tip I am using is as Peter
described. It has a center hole and smaller orifices around the
outside. If you cannot see them with your eyes, you should be able
to see the blue streaks emanating from them after you light the
torch and add the oxygen.

When I shut down my torch, I close the tank valves, light the torch
as I normally do and let the propane burn off. Due to the higher
tank pressure of the oxygen, there is still oxygen left after the
propane has burned off and I let this run out. Then I back out the
regulator screws then close the torch valves. I have been told that
releasing the pressure on the regulators when not in use helps them
last longer. I prefer to burn off the propane because I just don’t
like the idea of releasing a flammable gas into the room.

Hope this may provide some insight, Dale