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A warning and an advice to those using a 20 lb propane tank for their BenchSource

It’s not a safety issue but one of cost/convenience.

Recently I put together this setup using a splitter from the tank, two rubber hoses, and two torches that I had been using with the 1lb tanks.


This has worked well for me but one day I found both my torches will not work. Both had been working 100% with no problem the time before so I investigated why this happened.

I am not going to go through all the gory details but the long and short of it is if you use this setup, NEVER leave the torches plugged in with full propane pressure in the line EVEN if you turn off the valve at the tank.

What I found out is apparently propane at high pressure is a solvent for rubber and leaving a high propane pressure inside the hose for extended periods of time (we are talking weeks not hours please) can cause some of the rubber or whatever is in the hose to dissolve into the propane gas and when you turn it on the next time, this material will deposit at the nozzle and clog your torches.

If you unscrew the front of the torches, you will see that the gas comes out of a very fine nozzle, something of the order of 5-10 thousands of an inch, so they are very easy to clog. The good thing is they clog instantly and so you won’t find it changing over the course of an anneal.

I soak the tips of my torches in acetone overnight and was able to clear them. You can try using a fine wire to do this but good luck finding one that thin. However I have found later on that one of my dog whisker is actually more than fine enough to do this. Mine was a cast off by my dog and not one that I plugged… ;) and of course I found this out after I cleared it with acetone.

The proper way to use this setup is after you are done, turn off the gas at the cylinder and let the torches burn until all the gas is gone. Then turn them off for an added security.

Hope this helps anyone using this setup.
 
Most propane connection hoses available at big box stores are made of rubber, or some variation thereof. What type of rubber did you use?
 
Made in China maybe?

I can see all kinds of reasons to turn off the main tank valve after finishing a session. Letting the hose gas bleed off too, this is what I do with the 1lb tank set-up I use.

There's a valve at the torch end but I leave this alone as it's easier than re-adjusting it next time. Once flame dies (hose mostly empty) I unscrew the tank.
 
I close the tank valve at the end of my annealing, run the gas in the hoses until the flames go out and then take my 20 lb tank back outside to the patio; I don't want to leave it in my garage where the gas water heater is, just in case the propane tank has an issue with the valve. It's a bit more hassle, but a lot safer IMHO. YMMV of course.

Dennis
 
This is just a public service message for anyone who decide to only turn off the valve at the tank and leave pressure gas in the line which is not an unsafe practice. Just trying to reduce headache for anyone who might run in to this problem.
 
FWIW, the idea that propane under pressure will dissolve the rubber hose material and clog the nozzle was straight from the Benzomatic tech support. So I take that as Gospel.
 
FWIW, the idea that propane under pressure will dissolve the rubber hose material and clog the nozzle was straight from the Benzomatic tech support. So I take that as Gospel.

Wow, it has never happened with my camper or with my 5th wheel when it was set up in a park for two years. Maybe the orifice in the torch is smaller which does not allow these particle to pass. Good info to know. Thanks for the tip....
 
Thank you.
This is good info from the OP. Propane is heavier than air and so I always disconnect the tank and put a plug in the outlet if I'm leaving the tank inside. I'm not going to trust any valve if the result of it failing is my shop blows up.
 
Wow, it has never happened with my camper or with my 5th wheel when it was set up in a park for two years. Maybe the orifice in the torch is smaller which does not allow these particle to pass. Good info to know. Thanks for the tip....
I have the same in my camper all are hooked to my tanks with a hose and never have I had a problem. And the some connection go to small orifice . The bottle must be up right or you will get a liquid . Same as you get with small cans. Larry
 
This is good info from the OP. Propane is heavier than air and so I always disconnect the tank and put a plug in the outlet if I'm leaving the tank inside. I'm not going to trust any valve if the result of it failing is my shop blows up.

Hoz- Thank you, too. I took the exact same course in chemistry not once, but twice, much to my chagrin.
 
I have the same in my camper all are hooked to my tanks with a hose and never have I had a problem. And the some connection go to small orifice . The bottle must be up right or you will get a liquid . Same as you get with small cans. Larry
Larry, you don't have to believe me, I really don't care. I mean seriously do you think I am making this up? And yes, I know you have to use the bottle up right but do you think I have the 20 lb tank side ways????

Just trying to help people running pencil torches running this setup that as I have already mentioned have holes 5-10 thousands in diameter. This obviously IS a problem or I would not loose two torches together and the guy at Benzomatic would not have know this so well. BTW and FWIW, he even figured out I was doing case annealing without me saying anything. Pretty sure I am not the first guy he talked to with this problem.
 
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Same goes for your BBQ. Shut the main valve off when done cooking, then let the gas in the lines burn off before closing the burner valves. Common sense practice
 
Larry, you don't have to believe me, I really don't care.

Just trying to help people running pencil torches running this setup that as I have already mentioned have holes 5-10 thousands in diameter. This obviously IS a problem or I would not loose two torches together and the guy at Benzomatic would not have know this so well. BTW and FWIW, he even figured out I was doing case annealing without me saying anything. Pretty sure I am not the first guy he talked to with this problem.
The problem can be the wrong type of hose or the person did use the proper connection . Or didn't clean the inside before connection .
Larry
 
The problem can be the wrong type of hose or the person did use the proper connection . Or didn't clean the inside before connection .
Larry
I guess you never read my post where I said "FWIW, the idea that propane under pressure will dissolve the rubber hose material and clog the nozzle was straight from the Benzomatic tech support. So I take that as Gospel."

Some people just want to believe what they want to believe....:rolleyes: The saying "No good deed goes unpunished" applies here. What is your problem? Did you get out of bed on the wrong side this morning?
 
I guess you never read my post where I said "FWIW, the idea that propane under pressure will dissolve the rubber hose material and clog the nozzle was straight from the Benzomatic tech support. So I take that as Gospel."

Some people just want to believe what they want to believe....:rolleyes: The saying "No good deed goes unpunished" applies here. What is your problem? Did you get out of bed on the wrong side this morning?
No but I know taking the connection off won't fix the problem . If the hose is bad . Larry
 

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