Propane tank freeze

Stromberg Knives

Stromberg Knives

strombergknives.com
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Jan 3, 2015
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Hey guys!

I scoured through the old threads about propane tank freeze issues and solutions. But I thought I'd create a thread to get your view on this issue in 2019.

I have a three burner forge which I mainly use for making San Mai. When forge welding at high temperatures my propane tank (11 kg, 24 lbs) keeps getting too cold and therefore lose pressure.

What would be the best action to minimize this issue?
  • Get a electrical tank heating pad
  • Put the tank in water
  • Get a bigger tank
  • Get more tanks (a total of 2 or 3) and connect them all (in parallel or series?)
Your thoughts?
 
You can get out of date tanks for free, then take them to be recertifications. It’s about 1/2 the price of a new tank. I just did a 100lbs and two 40’s as I started forging again.
 
I found that the minimum tank size you need to prevent freezing is 50lb. Those 20lb bbq jobbers are a joke and you will fight them forever. WAYYYYYYY back in the day I would do a water bath on the 20lb tanks. But it’s not worth the hassle. I own a 50 and 100lb tank. Once we move to the new property/shop we will get a 100lb outside tank. That’s the smallest thy will drive out and fill. I do t forge much anymore but I would like to find time to and I have crap tons of bronze to make this winter.
 
My NC Whisper Low Boy (3) burner runs on a 40lb tank just fine.

The actual freezing occurs in the regulator, where the pressure drop freezes minute amounts of moisture in the tank. In my experience, the small tanks freeze just as bad when it's 110F in the shop as it does when it's 20F. So I never even tried to use bath water.
 
"The actual freezing occurs in the regulator, where the pressure drop freezes minute amounts of moisture in the tank. In my experience, the small tanks freeze just as bad when it's 110F in the shop as it does when it's 20F. So I never even tried to use bath water. "

Actually, NO
The freezing is caused by the liquid propane boiling off in the tank to create the gas that goes through the regulator. This is an endothermic phase change and the temperature drops. It will start to frost on the outside of the tank, and eventually will get to where the liquid propane freezes into propane ice. You could disconnect the regulator and open the valve and you would only get a trickle of gas. The tank has to rise to the point where the propane ice melts and becomes liquid again to get any amount of gas. Even on a warm day that can take half an hour or more.

Putting the tank in a large tub of water will help. Connecting two tanks together will also help. The real answer is to get a 100# tank from HF/home depot/etc. This will solve the problem and make trips to refill it much less often.
 
JTknives said:
I found that the minimum tank size you need to prevent freezing is 50lb. Those 20lb bbq jobbers are a joke and you will fight them forever. WAYYYYYYY back in the day I would do a water bath on the 20lb tanks. But it’s not worth the hassle. I own a 50 and 100lb tank. Once we move to the new property/shop we will get a 100lb outside tank. That’s the smallest thy will drive out and fill. I do t forge much anymore but I would like to find time to and I have crap tons of bronze to make this winter.
Click to expand...

Maybe I wasted money on the 40 pounders. Well, I can bbq a lot then. :confused:
 
Stacy E. Apelt - Bladesmith said:
"The actual freezing occurs in the regulator, where the pressure drop freezes minute amounts of moisture in the tank. In my experience, the small tanks freeze just as bad when it's 110F in the shop as it does when it's 20F. So I never even tried to use bath water. "

Actually, NO
The freezing is caused by the liquid propane boiling off in the tank to create the gas that goes through the regulator. This is an endothermic phase change and the temperature drops. It will start to frost on the outside of the tank, and eventually will get to where the liquid propane freezes into propane ice. You could disconnect the regulator and open the valve and you would only get a trickle of gas. The tank has to rise to the point where the propane ice melts and becomes liquid again to get any amount of gas. Even on a warm day that can take half an hour or more.

Putting the tank in a large tub of water will help. Connecting two tanks together will also help. The real answer is to get a 100# tank from HF/home depot/etc. This will solve the problem and make trips to refill it much less often.
Click to expand...
Propane freezes at -306F.

I'll agree to disagree.
https://www.marshallexcelsior.com/s...lator Reference Form 1001, Rev A, 2-10-17.pdf
 
tkroenlein said:
Propane freezes at -306F.

I'll agree to disagree.
https://www.marshallexcelsior.com/sites/default/files/MEC Freezing Regulator Reference Form 1001, Rev A, 2-10-17.pdf
Click to expand...
Dont confuse propane freezing point with its boiling point.
Fwiw,
I say Stacy incorrect that propane gets cold enough to become frozen in its cylinder.
Propane only has to go beneath its boiling point of -44°F. At that temperature its still liquid, but not boiling off vapour.
Just like most other liquid, the closer temperature drops to -44°, progressively less vapour emits until it stops.
 
Last edited:
If anyone bothers to follow the link I posted, it illustrates how propane's ability to "absorb" water is greatly reduced as it's temp drops. That is as little as 2 oz/500 gal. So, when your 20 lb bottle temp starts dropping so low because of the small tank capacity, it's ability to hold the water that's in it is reduced, causing the freeze up. As tank size goes up, the temp drop is less, and the ability to carry water is decreased less. So the hot water bath would help raise the temp of the propane, increasing its ability to carry the water. The larger propane tank fights the issue 2 ways. Greater volume of gas that slows the temp drop, and greater volume of liquid to be cooled.
 
tkroenlein said:
If anyone bothers to follow the link I posted, it illustrates how propane's ability to "absorb" water is greatly reduced as it's temp drops. That is as little as 2 oz/500 gal. So, when your 20 lb bottle temp starts dropping so low because of the small tank capacity, it's ability to hold the water that's in it is reduced, causing the freeze up. As tank size goes up, the temp drop is less, and the ability to carry water is decreased less. So the hot water bath would help raise the temp of the propane, increasing its ability to carry the water. The larger propane tank fights the issue 2 ways. Greater volume of gas that slows the temp drop, and greater volume of liquid to be cooled.
Click to expand...

I have always thought that the larger tank had an increased tank surface area to the ambient surrounding air. This increased tank area would absorb heat faster then the escaping gas could cool the liquid. If it was just that there was more liquid to cool before freezing then how come I can run a 50lb till it’s dead with out freezing up. Freeze up is a slippery slope as once you get ice on the tank your not warming the tank as efficiently because ice/water has a very large thermal capacity. Not saying your wrong or that I’m wright, just how I always thought of it.
 
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