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Lets talk torch heads

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Lets talk torch heads

Unread postAuthor: polk county » Sat Aug 30, 2008 9:20 pm

This is a multi question post designed to kick up a torch head discussion so that modern and dated ideas can be reviewed and compared.

1) What’s inside a bernsomatic torch head? I've heard gate valve, needle valve and check valve.

2) Is the Mr. Heater disposable cylinder adapter appropriate for propane injection? What keeps liquid propane from leaking into the regulator?http://www.bcarms.com/product_info.php?products_id=39&osCsid=52ccec8e0f699c0205b11f02e9e1882a

3) Some people cut the torch head off and secure a flexible hose to the shaft with a hose clamp. Doesn’t this cause the soft brass to collapse over time?

4) Some people unscrew the torch shaft from the valve housing with visegrips. Supposedly, the female threads in the valve housing are not NPT. Doesn’t the cost of epoxy required to seal the imperfect fit outweigh the benefit of not cutting threads in the stem. Can the valve housing be drilled out and rethreaded with NPT threads?

5) Has anyone found a torch head made out of something other than brass? Would and aluminum torch head be more durable that soft brass. Maybe the NPT threads cut into aluminum would allow more torque and prevent leaks.

Ideas and comments are appreciated.

Thanks
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Last edited by polk county on Sat Aug 30, 2008 10:17 pm, edited 1 time in total.

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Unread postAuthor: Radiation » Sat Aug 30, 2008 10:10 pm

Aluminum and brass are both very soft metals, but aluminum is softer than brass and would not be a good choice for NPT fittings. If cut properly a standard burnzomatic is more than adequate. If you look at 80% of NPT gas fittings they're brass. The real trick is making sure you tap it correctly.

The burnz torch head I have appears to be a needle.
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Re: Lets talk torch heads

Unread postAuthor: jimmy101 » Sun Aug 31, 2008 1:24 pm

polk county wrote:1) What’s inside a bernsomatic torch head? I've heard gate valve, needle valve and check valve.

It would have to be basically a needle valve since the required flow rate is pretty small. A tiny gate valve is functionally identical to a needle valve. A check valve is an automatic (uncontrollable) valve so that can't be it.

polk county wrote:3) Some people cut the torch head off and secure a flexible hose to the shaft with a hose clamp. Doesn’t this cause the soft brass to collapse over time?

Why? Every try to collapse a piece of brass tubing with a hose clamp? The hose + clamp will seal to the brass pipe long before you get to enough force to collapse the pipe. Heck, even with soft copper tubing you can get rubber hose + clamp to seal long before the copper will collapse.

BTW, no need to cut the torch head off, indeed all that does is increase the risk of getting liquid propane into your meter system, and makes the torch head unusable for it's original purpose. The small hole in the torch head does a very good job of insuring that any liquid that gets past the valve is vaporized as it goes through the orifice. All you really need to do is unscrew the air mixer, which can usually be done with your bare hands.
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polk county wrote:4) Some people unscrew the torch shaft from the valve housing with visegrips. Supposedly, the female threads in the valve housing are not NPT. Doesn’t the cost of epoxy required to seal the imperfect fit outweigh the benefit of not cutting threads in the stem. Can the valve housing be drilled out and rethreaded with NPT threads?

You really don't need NPT to get an gas tight seal. NPT is supposed to seal without the use of any sealing agents like pipe dope or Teflon tape. For regular threads, dope or tape will seal the joint just fine. Epoxy is overkill and unnecessary.
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Unread postAuthor: polk county » Sun Aug 31, 2008 6:36 pm

Thanks for the reply



Does anyone know where this video is? This link doesnt work. Its a vid about building a propane meter.



http://www.bcvids.com/dload.php?action=file&file_id=24
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Unread postAuthor: man_o_brass » Mon Sep 08, 2008 10:47 am

No idea on the video (I've been out of the game for a while), but I had great success with a very old torch by simply removing the torch neck and threading in a normal 1/4" brass air fitting with some teflon. It took alot of force and I'm sure the threads are screwed up, but I never intended to remove the fitting. It worked fine untill the seal around the valve knob failed rather spectacularly (much arm hair lost). Again, it was a very old torch, and they may have changed the thread size since mine was made. Certainly not the best solution, but I didn't have any NPT thread dies to cut/rethread the neck. You might try calling some local gas shops to see if they have the dies to thread it for you, as this would certainly be a better alternative.
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Unread postAuthor: SpudMonster » Mon Sep 08, 2008 7:00 pm

polk county wrote:This is a multi question post designed to kick up a torch head discussion so that modern and dated ideas can be reviewed and compared.

1) What’s inside a bernsomatic torch head? I've heard gate valve, needle valve and check valve.

2) Is the Mr. Heater disposable cylinder adapter appropriate for propane injection? What keeps liquid propane from leaking into the regulator?http://www.bcarms.com/product_info.php?products_id=39&osCsid=52ccec8e0f699c0205b11f02e9e1882a

3) Some people cut the torch head off and secure a flexible hose to the shaft with a hose clamp. Doesn’t this cause the soft brass to collapse over time?

4) Some people unscrew the torch shaft from the valve housing with visegrips. Supposedly, the female threads in the valve housing are not NPT. Doesn’t the cost of epoxy required to seal the imperfect fit outweigh the benefit of not cutting threads in the stem. Can the valve housing be drilled out and rethreaded with NPT threads?

5) Has anyone found a torch head made out of something other than brass? Would and aluminum torch head be more durable that soft brass. Maybe the NPT threads cut into aluminum would allow more torque and prevent leaks.

Ideas and comments are appreciated.

Thanks



1: It's a needle valve. I've disassembled them before for shits and grins.

2: Yes, it is. Don't position the tank so that the level of the liquid propane inside is above the outlet and you won't feed liquid.

3: Brass is soft but it's by no means jello. You will break the hoseclamp before you come anywhere close to deforming the torch-head. The wall thickness is very thick in proportion to the tube diameter.

4: The threads in the valve are not anywhere near NPT. Using epoxy to seal the threads to 1/8" NPT is pointless. Unthread the neck from the valve. Put the valve body in a vise and lock a big pair of visegrips around the neck. Make them nice and tight because it requires a lot of force to loosen the threads. Don't worry about collapsing the neck. I have never had it happen to me, no matter how tight I made them. Buy a 1/4" compression to 1/4" NPT adapter. Undo the compression nut and remove the sleeve. The compression threads are a perfect fit for the threads in the valve. Assemble them with a little loctite or thread sealant, and you've got a 1/4" male to propane tank adapter that will flow huge amounts of gas.
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5: Aluminum is softer than brass so it's a moot point. And I have never seen an aluminum torch head. Aluminum has a very low melting temperature so it would make for a lousy torch.
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Stupid quote of the now:
joestue "The chamber is rated to 100 psi, it don't say that on the side, but the 2 inch stuff is rated to 300, so by analogy..."
"only the last two feet hear the end is black cellular core"
"I'm taking it to 300 psi"
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Re: Lets talk torch heads

Unread postAuthor: SpudMonster » Mon Sep 08, 2008 7:04 pm

jimmy101 wrote:You really don't need NPT to get an gas tight seal. NPT is supposed to seal without the use of any sealing agents like pipe dope or Teflon tape. For regular threads, dope or tape will seal the joint just fine. Epoxy is overkill and unnecessary.


No Jimmy, NPT threads do require some sort of sealing compound to form a gas or liquid-tight seal. NPTF (dryseal) threads are designed to seal without sealing compounds.
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Stupid quote of the now:
joestue "The chamber is rated to 100 psi, it don't say that on the side, but the 2 inch stuff is rated to 300, so by analogy..."
"only the last two feet hear the end is black cellular core"
"I'm taking it to 300 psi"
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Re: Lets talk torch heads

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Unread postAuthor: chenslee » Tue Jun 09, 2009 11:10 am

Just ran across this.

The threads that join the the Berzomatic neck to the valve/regulator I think are 7/16-28 UNEF. Give up finding a tap or die for this size. It's bad enough that 7/16 is oddball, but the thread count is off in WTF land. To make matters worse, there is also a 7/16-27 UNS thread also listed in my book, so it could be that too. The reason people use vicegrips to unscrew this is because Bernz uses an acrylic glue to seal and bond it. Damn near impossible to get off.

If you are just metering propane out, your best bet is to use the rubber hose/hose clamp. The "steak saver" fitting assumes you have a regulator downstream and will spew propane, liquid or other wise, at 120psi (trust me I tried it). Not what you want.

I bought a bayou classic adjustable propane regulator and I use that with the steak saver. It works great. Remove the POL fitting and it's 1/4 NPT on both ends.



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Unread postAuthor: ramses » Wed Jun 10, 2009 11:49 am

since this topic was kicked up, I took apart a broken torch head, and the threads on the valve were 1/4" npt!
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Unread postAuthor: chenslee » Wed Jun 10, 2009 1:59 pm

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On this one the tube to regulator/valve connection is anything but NPT.

I needed the tube, not the reg, so I drilled out a 3/8 to 1/8 NPT bushing and epoxied it to the end thus adapting the tube to NPT. The reg/valve could probably be re-drilled and NPT tapped.
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Unread postAuthor: niglch » Fri Jun 12, 2009 8:44 am

BTW, no need to cut the torch head off, indeed all that does is increase the risk of getting liquid propane into your meter system, and makes the torch head unusable for it's original purpose. The small hole in the torch head does a very good job of insuring that any liquid that gets past the valve is vaporized as it goes through the orifice. All you really need to do is unscrew the air mixer, which can usually be done with your bare hands.

Does this mean that you don't have to go through the whole thread cutting process described at http://burntlatke.com/thread.html? If so, then the hose + clamp method seems like much less of a hastle (and a lot cheaper if you don't have proper thread cutting equipment).
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Unread postAuthor: ramses » Fri Jun 12, 2009 10:36 am

yeah, I went with the hose clamp method on my hybrid. It works better if you hacksaw off the end of the tube that has threads. Otherwise it leaks.
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Unread postAuthor: jimmy101 » Fri Jun 12, 2009 10:53 am

niglch wrote:
BTW, no need to cut the torch head off, indeed all that does is increase the risk of getting liquid propane into your meter system, and makes the torch head unusable for it's original purpose. The small hole in the torch head does a very good job of insuring that any liquid that gets past the valve is vaporized as it goes through the orifice. All you really need to do is unscrew the air mixer, which can usually be done with your bare hands.

Does this mean that you don't have to go through the whole thread cutting process described at http://burntlatke.com/thread.html? If so, then the hose + clamp method seems like much less of a hastle (and a lot cheaper if you don't have proper thread cutting equipment).

Yep, just unscrew the air mixer, find a piece of suitable sized hose and suitable hose clamps. The propane bottle's pressure isn't all that high so just about any kind of pressure rated hose will work, heck garden hose would probably work except the ID is too big.
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