I'm in the market for a mapp/air torch, and I notice that the new ones
(Bernzomatic, BZ8250 in particular) use a stainless steel burner. I've
always seen brass used in a torch end, from propane up to oxy/acetylene
setups, and I am wondering if stainless is such a good idea for the
application.
I do know that stainless and brass have similar melting points, but I've
seen stainless "rust" that after being exposed to hot/cold cycles (barbeque
burner).
Is my concern for the longevity of a stainless steel burner tip warranted?
Thanks,
Jon
I've used my MAPP torch set enough over the years, that if the burner tube
was subject to quick or even steady, slow erosion, it would've happened by
now, Jon.
I often run the fuel rate high enough to make the tube glow red (pretty much
wide open at the tank-top regulator valve), and it hasn't eroded much, if
any. It hasn't left any deep pits, or caused flaking of the SS.
I bought it at Sears, over 10 years ago (crap, maybe 20) and didn't expect
it to be a long-lasting torch, but it has been.
I can probably count the tools I've bought at Sears during that time on one
hand, but as we know, Sears doesn't manufacture anything but receipts and
flimsy, sometimes worthwhile warranties.
I guess the accurate answer is YMMV, as I have no idea what alloy the SS is,
or what materials are used in newer torches.
Even though some users will state that MAPP can't be used to braze steel,
the large one I have will do this, and I'm talking about steel bar stock,
not little strips of sheet metal.
This particular set included 2 torches that screw into the tank top
regulator, a light duty one about the same diameter as a common yellow
pencil, and a larger one.
I keep soft vacuum caps (the caps that are sold at auto parts stores for
capping off vacuum fittings) to keep dirt out of the inlets/jets (and
likewise covers on the tops of the tank fittings).
I don't think so. Look at oxy/act equipment, far higher temperatures and the
tips are
made of what looks to be copper to me.
The burning happens outside the tip with MAPP.
Wes
You can do steel brazing with propane - one of those swirl-torch gadgets.
It's got to be fairly small, and the bottle gets cold (and empty) pretty
quick, but it sure is handy for small jobs on a sunday - many places that
are open will have propane.
I'll offer some more description about the screw-on disposable tank-type
MAPP torch I've been using. The MAPP gas is meant to mix and burn within the
burner tube on all of them of this type that I've seen.
I know this seems weird, but the opening in the bigger mixer/burner "tip"
that I have is about 3/8" diameter. The last 2" of tube is where the
combustion begins.
I don't have any experience with a refillable cylinder, regulator and hose
type MAPP/air torch. I dunno if the construction has any similarities to the
screw-on type torch.
The orifice/jet is located at the base of the tube at a venturi (with
considerably larger air holes than a propane torch) where the gas flow draws
in air, then there is a twisted helix of sheet metal within the tube, which
I think is intended to swirl the mix to ensure that the air and the MAPP gas
are mixed.
Combustion begins to take place within the burner tube (in the last 2" of
length), which is why the end of the tube glows. Most of the flame that
exits the tube is blue, and extends quite a ways past the tube end,
especially when the regulator valve adjustment is close to wide open.
The smaller mixer/burner "tip" looks more like a conventional cutting torch
tip, only at the end, except the fluted center is set back inside about 1/8"
from the end of the stainless steel tube.
For this smaller tube, the combustion takes place outside/just beyond the
end of the fluted insert, so there is no red glow from the smaller tube/tip.
It should be mentioned here again, that connecting a MAPP gas tank to a
regular propane torch won't result in the same heat output as when MAPP gas
is used with a MAPP torch.
I haven't measured the temperature or heat output, but the performance is
about the same as just using propane, when using a propane torch.
As mentioned above, the air intake holes/ports at the venturi are much
larger on a MAPP torch, suggesting that the gas/air balance is a lot
different.
Propane will also work for those zinc/aluminum-miracle-repair type rods, but
MAPP is much better in that there isn't so much time (and fuel) wasted to
get numerous connections or joints done quickly.
I've had fabricating projects where the aluminum repair rods were used for
numerous joints using 1/8"x1" aluminum angle, and since aluminum dissipates
heat so quickly, using propane would've been miserably slow, if it could
have even been finished at all.
Back in my college days in the 1970s I put food on the table and gas in
the tank by repairing golf clubs. Used a propane torch about 2 hours a
day and had one I think was called a "turbo torch" or "tornado torch" or
something. it had a stainless steel tube and did burn inside the tube.
I went through a couple of bottles of propane a week and never had
any noticeable erosion of the tube in the 4 or 5 years I used it.
CarlBoyd
[ ... ]
O.K. I don't have a genuine MAPP torch.
Hmm ... my own experience, using the same torch, but starting
with a tank of propane, and then switching to a tank of MAPP, that I
could do small silver soldering with the MAPP, but not with the propane,
which suggests a bit more heat available from the MAPP -- whether it is
a higher flame temperature, or just better transfer of energy to the
workpiece remains to be seen. The workpiece was not surrounded by
firebrick (I don't have any, yet), and it had to be clamped in a drill
press vise, with the second part held on with some copper wire while the
silver solder flowed.
It might simply be that the MAPP torch in question is designed
to burn more fuel per unit time, so it needs more air for that.
Enjoy,
DoN.
Jon,
Brass melts at about 1980 F. SS melts well above 3100 F, some alloys like XB
and inconel are even higher. That's why SS is used in blast furnaces as
rolls, muffels and flame venturis.
Your copper alloys are used to wick away the heat into the torch body, which
they do much better than SS.
Steve
Thanks Steve, and you're right (I was looking up Al/Brass just before the SS
number, which let to my confusion). I did notice that the SS torch had a
longer tube extending from the plastic handle; perhaps that gives it the
additional distance to cool itself off.
About the only thing I don't like about the newer (stainless) torch is that
the air inlet ports are a part of the plastic handle, whereas on the old
brass unit they were upwards of the plastic handle, part of the metal just
before the burn area.
I can't help but think that when the plastic breaks, the newer model is
gonna be SOL, whereas on the old one, I'd just have to cobble up a new
handle and reconnect the hose.
Jon
while we're on the subject of brazing and temperatures.... I recently
had one heck of a time doing some brazing on a section of exhaust
pipe. I have a bernzomatic mapp torch(pietzo w/ swirl tip) and it was
barely hot enough to get the bronze to flow. the repair was chunky
and incomplete. I gave up and used an old hobby size oxy/mps(mapp)
torch(also Bernzomatic, the kind that uses the small cylinders, the
oxy last only a few minutes and costs $10 a pop). I used the mapp
(swirl) torch as preheat. still had difficulty.
now, I recall a few yrs ago my father had a brazing kit(Motomaster?
CanadianTire brand) with a bottle of "brazing fuel" with a "brazing
torch". it wasn't a swirl tip(rather it was long, bent, SS, rounded
in at the end), but it seemed hotter and easier to braze with,
unfortunately it was used up. the bottle was black, and just labeled
"brazing fuel". anywhere I ask about such an animal I'm always told
it was probably mapp.... but I don't get the same results using ye old
yellow bottles and the self-same "brazing torch"
I'd rather not have to go more industrial and buy a $400 pair of tanks
for my here-to unused Harris torch kit(bought yrs ago, never used),
just so I can do a little brazing from time to time. most of the work
I do is mig, so I find it hard to justify the tanks.
sugestions?
could the rod be the problem? too high a grade?
t.i.a.
-mark
The usual color (in the US) for acetylene tanks is black, Mark. There are
some common types of acetylene/air torches used in the HVAC trade to braze
AC lines.
With air introduced into the acetylene flow path, it will burn very hot
without making a lot of fluffy soot, like it does when the oxygen is turned
off using an oxy/acetylene torch.
MAPP is becoming available in large bottles, but I've only used the
disposable type small bottles.
I vaguely recall seeing a comparison chart showing various industrial fuel
gasses and their heat output values. Some searching would probably find
something similar.
MAPP gas is liquefied petroleum gas (LPG) mixed with
methylacetylene-propadiene. In Australia, it is known as RazorGas..
(wikipedia)
snip
I'd rather not have to go more industrial and buy a $400 pair of tanks
for my here-to unused Harris torch kit(bought yrs ago, never used),
just so I can do a little brazing from time to time. most of the work
I do is mig, so I find it hard to justify the tanks.
sugestions?
could the rod be the problem? too high a grade?
t.i.a.
-mark
I think you will find that $ spent getting your oxyacetolyene torch able to
work will be $ well spent - it is much faster, easier, and more versatile
than propane/mapp
Those are both a joke - the Bernzomatic is like One Cubic Foot of
Oxygen compressed at a few hundred PSI, totally worthless. And the
Oxygen Generator that took the pyrolytic sticks are just as worthless.
Air-Acetylene torch, sold for plumbers and pipefitters - Prestolite
being the most popular. Comes with the ~50 CF "B" Acetylene bottle,
the smallest practical home bottle. I've done a LOT of silver braze
with one where my boss said I needed Oxygen. Not if you know what
you're doing...
(The ~10 CF "MC" Acetylene cylinder is another waste of time - since
you can only withdraw 1/7 capacity per hour, the flow is too small for
anything other than a motorcycle headlight - which for some
fascinating reason is why it's called a MC Cylinder.)
You don't need to get the lease sized 200CF industrial tanks - a
50CF Oxygen and a B Acetylene should set you back $250 purchased brand
new and filled, a LOT less if you haunt garage sales and pick up a
used set. And they are yours forever - the smaller tanks are always
owned.
( The big ones can be owned or leased, and that's where keeping the
paperwork is important. Because if the tanks have a neck collar for a
local supply house and you can't come up with the paperwork that says
you own a set when you take them in for a refill, they can take them
back as stolen.... )
Harris and others make Air-Acetylene torch handles and tips, and
they can be used with any welding regulator and tank. So you don't
have to find an 'Antique' Prestolite.
Just be careful - Read up on care and feeding of bottles. Go
slamming and banging them around and break the matrix inside the
acetylene bottle, and they can't be refilled and must be destroyed.
Can't let the acetone get out or contact between acetylene and pure
copper - copper acetylide salts go BOOM. Can't let line pressure rise
above 15 PSI outside the cylinder, or the gas can go BOOM! Must have
arrestors in the gas lines, let that shockwave get back to the tank,
and the BOOM! gets real big.
Oxygen can't be treated cavalierly either - Can't get any oil or
grease at ALL In the Oxygen path that isn't specially formulated for
the use (and used in controlled quantities) or it can make mayhem too.
And sometimes when the surface you are trying to braze will not tin
for nothing or nobody, you have to get it hot /then/ scrub it down
with more flux and a stainless wire brush. And all of a sudden it
decides to clean up and wet with a vengeance.
-->--
now, I recall a few yrs ago my father had a brazing kit(Motomaster?
CanadianTire brand) with a bottle of "brazing fuel" with a "brazing
torch". it wasn't a swirl tip(rather it was long, bent, SS, rounded
in at the end), but it seemed hotter and easier to braze with,
unfortunately it was used up. the bottle was black, and just labeled
"brazing fuel". anywhere I ask about such an animal I'm always told
it was probably mapp.... but I don't get the same results using ye old
yellow bottles and the self-same "brazing torch"
I'd rather not have to go more industrial and buy a $400 pair of tanks
for my here-to unused Harris torch kit(bought yrs ago, never used),
just so I can do a little brazing from time to time. most of the work
I do is mig, so I find it hard to justify the tanks.
sugestions?
could the rod be the problem? too high a grade?
----------------- response below --------------------------------
Well, I am not a welder (IANAW), but in my "research" for this torch I found
these guys using the previous version of the Bernzomatic (JTH7 - Mapp/Air)
to build bicycle frames:
formatting link
So, at least from those guys, mapp/air can be used to braze.
In any case, it looks like I'm probably going to pick up the newer version
mapp/air torch. I noticed that the forge guy is using one on his
mini-forge, and seems to like it better than the old one, which is good
enough for me.
Jon
I'm fairly certain that this particular model of MAPP torch that I've been
using has a higher fuel delivery/burn rate than any propane torch I've used,
since the length of the blue flame extending from the swirl chamber/tip is
much larger diameter, longer and louder than with any propane torch.
I suspect that there are many variations in the designs of all the available
portable torches. I see some propane torches at stores now with huge burner
heads on them (over 1" diameter), when years ago, they all looked about the
same.
I haven't looked, but I would doubt that there are any readily available
specifications available for orifice sizes or CFH cu-ft/hour rates for these
portable torches.
My original reply was YMMV, as I would expect that there are many
differences in portable torches, especially related to cool-looking and
cheaper to manufacture products.
I have a couple of types of these, I only use propane in them, though,
I have O/A equipment for the really hot requirements. On one, the
burner will glow dull red after extended running, it's a "turbo" or
"tornado" type of burner, and even with propane, it's much hotter than
the older 50s-60s Bernzomatic-style burners. Those old ones just got
stuffed in the bottom of an old tool box. All that happens with the
stainless burners is that they get a nice blue color, which doesn't
affect functioning at all. Unless you use it 24/7, I think your
concerns are groundless. I've got one I've used extensively for 10
years.
Stan
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.