20lb Propane Tank Pressure Loss???

R

ritzblitz

Joined
Dec 31, 2006
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So last night I went out side after work to fire up my one brick forge.

I noticed that I was not getting any significant pressure out of my 20lb tank and I was disappointed. I couldn't get it to run nearly as hot as I wanted. The flame it produced reminded me of when a small 14oz tank is about to run out and it is just barely running. The temperature was pretty low last night. Although I don't know if this makes a difference, I would estimate in the 20's. I switched the torch back onto a 14oz tank and it had plenty of pressure and produced a flame hot enough for my liking. When I run off of the 20lb tank, I usually open it up all the way then regulate it through the torch valve.

My torch setup goes like this: propane tank > adapter hose > JTH7 torch.

So if someone can tell me what's going on here, I would REALLY appreciate it!

Thanks in advance!
Alex
 
If you're putting out a lot of gas volume, particularly when the tank is in a cold area, you will lose pressure. After a while, ice will form on the outside of the tank. The bigger the tank, the less likely it is that this will happen. I just switch tanks. I have heard of guys putting their tank in a tub of water to keep the temp up.

Another thing. On the new tanks with the Overfill Protection Device, if you don't have the connection pretty tight to the tank you will not get full pressure. The male end pushes in a valve inside that lets the gas flow.

Luck.
 
i had a problem like this one time soldering some copper tubing on a plumbing repair. i suggest that if you are going to be using the tank for your forge to disconnect it before the temp out side starts to get cold and just keep it inside somewhere warm. remember that its LP which is a liquid that expands to create the gas. when liquid is in freezing temps it tends to shrink and in some cases become ice. with it being ice it can produce the gas you need. therefore it acts like it is running low. try wrapping a couple of heating pads around it if you left it outside in the cold and that should warm it up enough to expand to create the proper pressure. hope this helps.
 
yes. you can also use the method that r.coon-knives suggested of sticking it in a tub of water. just make sure the water is warm and stays warm.
 
Most makers who forge a long time ,or run wide open (damascus) will freeze up a 20 pound tank . Switching to a 100 pound tank will solve this nicely. You can also just switch from one #20 tank to another and let the frozen one warm up ( this is what I do when forging at a demo). What happens is: As the gas boils off it absorbs heat (endothermic) and the propane gets colder and colder . Eventually it starts freezing into propane ice, which sublimates much slower than the liquid boils, thus lowering the pressure. If you shake the tank you will hear it rattle.( Shaking will also temporarily bring the pressure up).
Stacy
 
thanks for explaining that better, Stacy. i like that idea of switching bottles. makes things alot faster.
 
Ritzblitz I went through the same thing as you when I first started out trying to heat metal.I had the same setup as you.
20# Tank,adapter hose and the same torch.
The adapter has some type of regulator in the connector where it screws into the tank.It will only let so much propane thru at one time.
I tried to "alter,bypass,get rid of",this regulator with no luck at all.

You might want to expand your horizons and try for a little bigger forge with proper insulation such as kaowool coated with the ITC100.
Take a look at this burner setup ,and decide for yourself.

http://www.backyardmetalcasting.com/oliverburner1.html

I used this burner in a freon tank with proper insulation,and this baby gets hot.
 
you can also try the Indian George style forge. his design i simple. the cost for the burner kit is about $50. that doesnt include the blower or the propane assembly. for the blower you could just grab an old leaf blower and hook it on.

http://www.indiangeorgesknives.com/building_a_forge.html

also he suggest that instead of using the elbow to use a T and a cap. just drill the hole thru the cap. its really easy to make. i made mine. heres a link to the pics of my forge.

http://www.bladeforums.com/forums/showthread.php?t=459254
 
im not to savy on propane but ive worked with co2, which seems to have somewshat similar properties just mroe extream. between cold to hot the psi out put could vary a lot (remember this is on co2, but it could go from 500ish-1800 on a "full" fill just depending on the temperature)

i assume propane has a similary pressure to heat relation, there fore it probably expotentialy increases pressure when temp goes up thus the opposite happens when it cools.

remember propane is running about 400s IIRC at 72*F again IIRC so if it gets really cold its probably gona go down in psi output.

-matt
 
I strapped a heat pad to the tank and I will go back tomorrow and see if that brings the pressure up some.
 
you only need to give it about 30 mins to an hour. to make it warm up faster put the heat pad on it while you have it indoors and then keep the heat pad on it while its outside. it might take 2 heat pads. depending on the weather.
 
I use a small electric space heater with fan from Wally World-$24.00. I can run full blast from full to empty without losing any pressure. Just set it close blowing right on the tank.
 
Was the adaptor hose made specifically for your tank? What kind of shut off does it have ? Needle valve or a regulator of some sort?
You have to have the right valves and fittings to get much pressure out of a propane tank.
Also, if I remember right, there is a valve inside the tank that shuts off if the internal pressure drops too abruptly. Thats why some of the larger grills have a specific lighting sequence. I've never had that trouble with a high pressure regulator, but it might be an issue with your set up. Trying turning the pressure up gradually and see what happens.
 
You guys are missing the point. It has NOTHING to do with the ambient temperature, or much to do with the tank temperature. Warming the tank first, putting it in a tub of water (this does help a bit by increasing the thermal mass), and other warming methods won't stop the propane from freezing. I have had tanks freeze up while forging in 95 degree summer days. It has to do with the cooling effect of the propane vaporizing from a liquid state. Getting the proper regulator, valve,hose setup from Darren Ellis will help some, but won't change physics.

BTW: If the orifice in your forge is too large, freeze-up will be worse.

Stacy
 
You just suffered can freezing. Nothing to worry about.
Just put the tank in a can of water. You don't need it to be hot. Actually, even cold water works fine. Warm is better.
Gas is in a liquid state in the can. Evaporation subtracts heat. You use gas, it evaporates, it subtracts heat to the can, freezing it. Low temperature reduces pressure. That's all.
 
I'm just confused because I was barely using it before. The second I turned it on I had pressure loss. It had been sitting for a day untouched (but in the cold).

Thakns.
 
OK Now. That is a different thing. I would look for an orifice blockage or a stuck regulator (and as R.Coon asked, Is it the right regulator). The propane does boil off at a lower pressure on cold days, but it has to be really cold for it to affect things greatly. How cold was it?
Stacy
 
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