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Freezing Propane Tanks. A Different Solution


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#1 maddog

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Posted 05 December 2010 - 08:40 PM

It's worse in the winter of course but it's a problem even in the summer. I am totaly fed up with schlepping tubs of water. If I forge all day, I have to refresh the water at least once. If I leave it till I see the pressure fall, I have to melt off the thick jacket of ice that's formed. If I dont remove the tank when I leave and leave it overnight, I have a propane tank in a large block of ice. I dont have room in my shop for multiple tanks. I don't even have the extra room for the water tub.

Anyway, I got the guts of one of those hot air hand driers that they use in public restrooms and set it up to blow on the propane tank. No more frost!! The tank is pleasantly warm to touch. I set it up to run off the same switch as the forge blower and now that there is no tub, the tank and the blower fit neatly under the forge table so its all very compact. I estimate the blower runs lower wattage than a regular hair drier. More vol, lower temp. It's thermostat controled. Today wasn't very cold. If it's not hot enough to overcome sub zero weather, I will move the thermostat.
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#2 maddog

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Posted 06 December 2010 - 11:56 AM

I already posted this thread but it seems to have vanished into the Twilight Zone, so if this is a duplicate, I apologize.

I am fed up with this bidniss of propane tanks in a water tub. On a full day of forging, even in the summer, I have to replace the water with fresh warm water several times. If I leave it too long, I have to fight a thick jacket of ice on the tank. In the winter, if I forget to take the tank out when I leave, I have a tank and a tub frozen together in a large block of ice. Space is very tight in my shop, the tub takes up extra floor space that I cant afford. It's large and awkward to carry when its half full of water. I don't have the space to manifold several tanks together and I doubt that would work in the winter.

Yesterday I took the guts of one of those hot air hand dryers they install in public restrooms and set it to blow on the tank. No more frost!! None!. It's hooked to the blower switch so I dont have to think about it when I start the forge. Without the water tub, the tank and the blower fit neatly under my forge table, saving a lot of space. I am guessing that the hot air blower runs less watts than an ordinairy hair dryer. More volume at lower temps. It's thermostaticaly controled. I haven't tried this out in sub freezing weather but if need be, I can move the thermostat to get warmer air. As it is the propane tank is pleasantly warm to the touch.

The thread was removed due to concerns about safety. The post DID NOT vanished into the Twilight Zone. We were consulting a propane dealer to get their opinion so we could return that information from a known source.
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#3 Steve Sells

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Posted 07 December 2010 - 03:14 PM

Normally when a tank is frosting up, it is caused by the gas exiting faster than that size tank should be emptied. The correct solution is to use a larger tank, if you can't reduce the flow.

Your idea of heating the tank is just treating a symptom, you corrected nothing. Simply this is an OSHA violation and serious fire explosion hazard as well. But you have built a nice little bomb.
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#4 ThomasPowers

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Posted 07 December 2010 - 04:05 PM

I sincerely doubt that system is going to get any hotter than a tank will just sitting in the NM sunshine in the summer.

If that's ok; just how will it be a bomb in the winter? By tying it to the blower it's never heating without gas exiting anyway so no cook off of the pressure valve.

I am a bit interested in his system. Here in central NM I can run a tank all the way down to flat in the summer without having it ice so much I need to warm it. Are you using a large forge? (The winter is different of course).
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#5 cavala

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Posted 07 December 2010 - 05:08 PM

Normally when a tank is frosting up, it is caused by the gas exiting faster than that size tank should be emptied. The correct solution is to use a larger tank, if you can't reduce the flow.

Your idea of heating the tank is just treating a symptom, you corrected nothing. Simply this is an OSHA violation and serious fire explosion hazard as well. But you have built a nice little bomb.


You're talking about a BLEVE and I don't think he's going to reach the boiling point with that setup.

#6 maddog

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Posted 07 December 2010 - 05:21 PM

Normally when a tank is frosting up, it is caused by the gas exiting faster than that size tank should be emptied. The correct solution is to use a larger tank, if you can't reduce the flow.

Your idea of heating the tank is just treating a symptom, you corrected nothing. Simply this is an OSHA violation and serious fire explosion hazard as well. But you have built a nice little bomb.


Actually using a large tank is just treating the symptoms. The cause of freezing is heat being drawn from the cylinder faster than it can be replaced. A warming blower addresses that directly. So does a bath of hot water. Large tanks work because they have a greater thermal mass which usually doesnt get depleted in a day's work.

In my shop, *any* size tank will freeze in cold weather. Plus I dont have the $$ to go buy a couple of 24gal tanks. I run a small forge but I run it hot. A 5 gal tank lasts me about 8hrs.

This is a thermostaticaly controled blower designed to produce air at a temperature that is comfortable for the skin. Even without thermostat control, the blower simply doesnt produce enough heat to get the tank hot. The pressure relief valve opens at 375 psi. The vapor pressure of propane at 100F (quite a bit hotter than my system) is about 200 psi. There is absolutely no possiblity of the tank bursting. The worst that could happen is that the relief valve starts cycling and bleeding gas out of the tank. That too could be serious if it went unnoticed. But as I said, my setup doesn't come close.

Finally, as Thomas pointed out, the blower only runs when the tank is drawing which means I am only warming it when it's cooling.
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#7 Glenn

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Posted 08 December 2010 - 04:05 PM

Anything you do to squeeze more propane out of a tank faster than that size tank is designed to deliver, is questionably dangerous.

The correct answer is to consult the propane distributor and have them look at your set up and recommend a proper sized propane tank and distribution system. You will get better service to the forge, most likely a better price on the propane (due to buying in bulk) and the distributor takes the responsibility for the system.

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#8 ThomasPowers

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Posted 08 December 2010 - 07:03 PM

So Glenn: my system is designed OK in the summer but in the winter my exact same system is not OK? Seems to be something odd about that.
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#9 Glenn

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Posted 08 December 2010 - 07:25 PM

Maddog is from New Mexico, and posted concerning the problem in December. I would suggest that the seasonal difference in ambient temperature and or humidity may be a factor. If he were to design the system for December temperatures, I doubt that he would have a freezing problem in the summer. I would suggest a design that would factor in high heat and sun found in that part of the country.

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#10 maddog

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Posted 08 December 2010 - 10:48 PM

Anything you do to squeeze more propane out of a tank faster than that size tank is designed to deliver, is questionably dangerous.

The correct answer is to consult the propane distributor and have them look at your set up and recommend a proper sized propane tank and distribution system. You will get better service to the forge, most likely a better price on the propane (due to buying in bulk) and the distributor takes the responsibility for the system.


I just don't agree with this. What I am doing is really no different than putting a tank in a tub of warm water. I am not heating the tank above its safe operating temp (about 100F) in fact the blower keeps it cooler than a tub of warm water. It just doesn't feel cold to the touch. I am not raising the pressure inside the tank to anything abnormal. It's at the right temp and the right pressure. What's the problem?

If I were running a commercial shop I would invest in a professional class propane system. I would also make sure that my plumbing and venting was strictly up to code and that the forge was an approved device with the appropriate safety features. To buy a couple of 24 gal tanks, or to have a permanent tank installed runs about $400 right now. And I suspect my county ordinances wouldnt allow a permanent installation in a residential area. I own 8 5gal tanks which I would have to discard. How much barbecue can one person eat?

I am doing what thousands of other hobby smiths are doing. Running my forge off small tanks and solving the problem of freezing by adding a moderate amount of heat. People seem to think I lit a camping stove under the tank or put it on an electric hot plate. It's a hand drier for crying out loud. Its not even as hot as a hair dryer. It's like a warm summer breeze. Come on guys. Let's get real here.
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#11 Glenn

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Posted 09 December 2010 - 12:49 AM

I reread your post and to my way of thinking the 5 gallon tanks are too small. You would have to go to town once each day (8 hours of forging) and have it refilled. A 24 gallon tank should last you 5 days (38 hours of forging), and with a 100 gallon tank, it should allow you to forge each and every day for three weeks (160 hours of forging).


Come on guys. Let's get real here.

Please do not take the discussion personally, as it is a problem anyone with a gas forge any where in the world might experience. It is a discussion on propane tanks freezing up, the cause of the freeze up, and how to safely solve that problem.

The amount of propane needed for THAT forge is the same, whether it is a commercial shop or a home/hobby shop. The correct answer is to get a larger tank. A second answer is to gang several tanks together so you can create the volume you need, and not overrun the draw down amount of any one tank.

If someone questions your standards, they are not high enough.

Do not build a box, that way you do not have to think outside the box.


#12 maddog

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Posted 09 December 2010 - 01:50 AM

No I don't take this personaly It's just that I find the level of caution and alarm in this thread incongruous and disproportionate. After years of people talking about warming their small tanks in tubs of water we suddenly get bothered about a little warm air.

Well OK if we are now going to consider the topic at large. Should people be putting their tanks in baths of warm water at all? Perhaps people simply shouldnt be using 20lb propane tanks at all for their forges. It's worth thinking about. Propane is dangerous and many members of this forum use it. It would be a valuable thing if we took a close look at the common practices with propane in smiths' shops. I personally am concerned about the exposed fuel lines in the presence of hot iron. I think they should be protected.

But so far no one has explained what the danger is from warming the tank if this is done with reasonable caution. Sure it's not ideal and it's inconvenient. And if I were buying propane tanks today I would do it differently. But It didn't work out that way and now I have a herd of small tanks. I am not going to spend $400 to revamp my setup right now. Not unless I am convinced there is a significant risk involved. As for refills, I just take them to be filled all at the same time.

It's not enough to say the tanks weren't designed for that kind of draw. We are smiths we think for ourselves. We often use things in ways that werent intended by the manufacturers and we take pride in it. OSHA and general safety regulations are written with a very broad brush. If I am not running a commercial outfit and am not forced to comply with these regs, I can make a more fined grained and intelligent decision. I don't see the point in slavishly following OSHA regulations.

The small tanks aren't speced to draw at this rate because they can freeze up. They are designed to handle a certain temperature and pressure and as long as they stay within their limits they are quite safe. Freezing tanks could cause an accident. If the pressure drops and the flame goes out while the unit is unattended and somehow the tank starts warming again and releases unburnt propane. Could happen. If you are writing a policy for the whole population you have to worry about such possibilities. You certainly cant tell people its ok to warm up their tanks. Some idiot will put one on the stove. These tanks are used at barbecues where kids and dogs are running around. People are sometimes drunk.

On the subject of manifolds I am curious to know if this is an approved procedure and if there are any special requirements for their construction?

I agree we should consider the dangers carefully. But let's make a reasoned, intelligent assesment of the risks.
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#13 Ramsberg

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Posted 09 December 2010 - 04:12 AM

Hey MadDog,

This might be what you are looking for.

http://www.regoprodu...r_manifolds.htm

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#14 arftist

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Posted 09 December 2010 - 05:06 AM

My Johnson #122 forge uses a good volume of gas. It runs well on two 20# tanks manifolded together.

#15 Sweany

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Posted 10 December 2010 - 09:42 AM

I found this on freezing tanks. Rather long and scientific.
BUT he explains the reason why the tank freezes, why the tank freezes at certain times of the year, at the end he cautions about heating a tank with any heat source (point of ingnition in the event of a leak)

However I do believe my forge would qualify as a point of ignition, so would my gas grill in the event of a leak...... Checking euipment is a good thing.

my .02

http://www.wardburne...tankfreeze.html
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#16 maddog

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Posted 10 December 2010 - 01:50 PM

I found this on freezing tanks. Rather long and scientific.
BUT...http://www.wardburner.com/tankfreeze.html


Interesting article and thankyou but it seems confused. The pressure in a tank of propane depends soley on the temperature of the liquid propane within it. It matters not whether the tank is 1 gal or 5000 gal. The basic problem is NOT BTU delivery but pressure! When temperature of the liquid propane falls, its vapor pressure drops and at some point, it becomes insufficient to drive enough propane gas through the forge orifice to keep it running. A 5000gal tank cold enough to frost up on the outside will not keep a forge going any better than a barbecue sized tank. It probably can deliver far more BTU than the forge requires but not at the necessary pressure. Propane Info

As far as fuel delivery rates are concerned bigger tanks differ from small ones only in that there is a larger volume of propane which has to be chilled before the pressure falls too far and they have a larger surface area through which to replenish the lost heat. A 100gal tank sitting in a subzero shop will eventually fail to deliver propane at the required pressure. The only question is whether that happens before the day ends. A 100gal tank with only 5 gals left will probably perform about the same as a 5gal barbecue tank.

As for the possibility of a BLEVE, modern tanks have an over pressure release valve set for about 375 psi. If the tank gets too hot, this valve will start opening and closing to relieve the excess pressure. This will release unburnt propane into the air which is also not a good thing but it's nothing like a BLEVE.

A propane tank in a blacksmithing shop is surrounded by ignition sources: the forge itself, the hot work piece, flying scale etc. The extra risk posed by glowing hair dryer coils seems insignificant. Nor is it necessary for the coils to run red hot in order to maintain the heat balance in the tank.

The recommended max temp for free standing propane tanks is about 110F at which point the pressure is about 200psi. This is a very conservative limit. 200psi is only half the pressure needed to crack the relief valve and you can be sure that that pressure, 375psi, is set way below the point where the tank is in danger of bursting. I am sure my tanks sitting outside on a hot summer day routinely exceed 110F. But, to be cautious, the tank, when touched should be no hotter than body temperature. This means that if you put it in a bath of hot water, the water should not be scalding hot if you want to stay within this guideline.

I doubt this applies to anyone here, but if you were seriously considering lighting a wood fire under your propane tank to keep it warm, there is probably no advice or warning that is going to save you from yourself except perhaps that you should make sure your will is up to date. It will be needed sometime soon.
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#17 Sweany

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Posted 10 December 2010 - 02:34 PM

I doubt this applies to anyone here, but if you were seriously considering lighting a wood fire under your propane tank to keep it warm, there is probably no advice or warning that is going to save you from yourself except perhaps that you should make sure your will is up to date. It will be needed sometime soon.


sometimes stupid cannot be overcome...

I was working in Iatan MO one winter, actual temp reached near -50, acetylene came out of the torch in liquid form, you could fill a cup and light it like a candle.

I believe heat rise in a large tank is not as significant as in a small tank at the same temp.
It would seem that it would be harder to reduce the temp in a large tank by taking gas from it.

I suspect that the colder gas also affects the regulator.
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#18 maddog

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Posted 10 December 2010 - 06:03 PM

Since this thread has raised concerns about safety and the possibility that someone might actually follow my example and hurt himself let me make a couple of things very clear:

My intention in starting this thread was only to share what I had done with my propane setup. I do not mean to say or imply in anyway that I am assuring people it's safe for them to do. I consider it safe enough for me to do. If you choose to follow my example, you must make your own decisions about safety and consult qualified sources for information. It is your responsibility to understand the risks involved and your decision to accept them.

I am not qualified to tell people how to use propane safely. I have no formal training and my informal knowledge is haphazard.

Anything I say on the subject of propane safety is for purposes of discussion only.
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#19 pkrankow

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Posted 10 December 2010 - 07:15 PM

I use cold tap water in the winter with my 20# tank. Works good as long as you only expect 2 hours of working time.

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#20 CurlyGeorge

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Posted 10 December 2010 - 10:04 PM

I'm still a "Gasser Rookie", and don't do any long forging sessions with my forge. Most of the time I'll only run the gasser for 1-1 1/2 hrs and shut it down. Now, I have been firing up the woodburning stove to heat my shop up, before forging. But I have not, so far (Knock on wood), had even a frost line on my tank. I'm not sure if heating the shop up first is why, or not. But I have been paying attention to that since reading the posts about tanks freezing up.
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