Propane Freezing Conundrum

clanderson

clanderson

Joined
Dec 18, 2012
Messages
90
After filling up my 20lb bottle of lp about twice a month, I finally gave in and bought the 40lb bottle I stared at every time I filled up at my local Ace.

I lugged the newly filled bottle into my shop and hooked it up to the forge, excited at the prospect of my forge not slowly dying of asphyxiation halfway through another project.

After about ten minutes of work however, I noticed my burners beginning to sputter, and the roar of the forge turned into a calm bonfire of dangerously high flames. I looked down and noticed my lines and regulator had completely frozen over; I shut off the tank valve and let the pressure in the lines bleed. The tank showed no signs of frost or abnormally low Temps. I let the lines cool and started again. Another ten minutes in, a repeat.

Could somebody help me understand what might be going on here? My 20lb bottle never exhibited this behavior, and from what I've read, a larger bottle should be more tolerant to the thermal related woes of lp phase transitions. Is my regulator failing? Bottle overpressured?

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The new bottles with triangular valves have leakage protection. I don't know if that's your problem.

From what I see, it's not the bottle or valve. It looks like the hose and regulator

You could try a few metal coil loops before the regulator.
Let it heat up before it hits the regulator.


You could try higher heat in the room.


Some folks have used an electric heating pad under the tank. That seems risky but I bet it works.

The water tub.

Watertub with magnetic oil pan heater.
 
There are commercially available propane tank 'electric blankets'.
If you had asked before buying your new tank, I would have suggested a 100# tank...
 
You may be running the regulator too high. If the lines are freezing up, that is where the pressure drop is happening. It could be a bad hose.

The possibility I see is that you are pushing liquid propane into the hose. The tank may be a tad overfilled and the warm shop has expanded the liquid propane. The problem should go away as you use some of the tank up. If not, I would look at new and larger propane hoses to the forge.
 
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This is weird. Stacy is right that there is a pressure drop at the regulator (along with a temperature drop due to pv=nrt) but the REAL temperature drop is due to the phase change from liquid to gas (which the OP mentions), which occurs in the tank. Stacy may be right that youare pushing liquid into the regulator, and that this will settle out as the tank gets lower.

Keep in mind that ice on the outside of the hose and regulator really means nothing at all - as the *inside*, which should have nothing but propane (no ice) is what really matters. As the tank cools down, propane evaporation should slow down, but all but stop? Not really. Random things that come to mind ... contamination in the propane (which should go away with use), faulty regulator (which you can test by firing things up with your 20# tank), in general a colder ambient (and so colder liquid in the tank than you experienced before (so try weo's tank heater), non water contaminants in the propane (which i think unlikely...)
 
You mention "burners", could turn on only one burner and see if the problem goes away? In trying to forge with 20 lb I had problems with tank freezing (frost on outside) when forge was really going. I changed to 100lb tanks and no more problem. Not sure about your problem since you say there is no visible frost on outside of tank or hoses.
 
Good idea, Ken!

If the answer to Ken's suggestion is "success!": Do your burners have jets? Reduce the size and see if you can still hit temps. Still, with an iced regulator but not-iced tank, that regulator falls into question...

Good luck!
 
I can run a 20# tank on my forge without issue if I keep a fan blowing on it (inside a heated shop).
 
I worked one place we're we used CO2 bottles for shield gas when welding. We just had to put heat lamps or tape on the regulator during the winter time and I kept a spare regulator on hand when my regulator froze up. There are probably better ways but it can be a problem during the winter if you are using large volumes of gas even if it isn't the same type of gas.
 
Could be water in your tank, or as others are saying liquid propane hitting the regulator possibly due to an over filled tank. Most propane lines are pre made with the fitting and regulator mounted at the tank with almost no separation. But, you can get twin stage regulators that are designed to prevent freeze up. Not sure if they drop the pressure too low after the second stage for your burner. You can also get an extension hose in front of the regulator with coils.
 
The modern 20/30/40 lb tank are good for about 80,000 BTU output without freezing up, and a max output of about 120,000 BTU before considering it a "leak" and restricting flow. Two 80k burners are going to trip the safety features in a single tank. I'm unsure of the ratings for 100 LB tanks, but they really can't output much more. It's all about the surface of the liquid evaporating, and 20/30/40/100 are all the same diameter tank, meaning they can only evaporate so much at a time without causing issues.

20 LB tanks are designed for 20,000 BTU BBQ grills, not forges that output more BTU than the average household furnace.

Two 20 LB tanks linked together have a higher output max than a single 100 LB tank.
 
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