Propane and Cold Weather

[JRFISHBAIT]

Now that we have extremely cold weather here, people are bound to have problems with their heaters and propane tanks. In extremely cold weather, it is important to keep your tanks as full as possible. When the temperature dips, so does the pressure in your tank. When the pressure drops, the liquid won't vaporize. The only way around this is to keep your tanks full so the pressure stays up.

This may be considered an advertisement, but we will work with you to keep your tanks full. Normally we have one charge for a tank fill, but if your tank is 1/2 or 2/3 full, we will work with you on this. I'd rather see your heater work properly and you safe and warm in this cold weather.

Joe, Matt, Katy and the gang

[MNfan]

How full the tank is not the issue it the temp propane vaporizes at which is -30 so the closer the air temp gets to that the less vapor you create which lowers the pressure.

[Kyle Sandberg]

MNfan, tank fullness does have something to do with it. If you only had 2 pounds in a tank at -20, you won't be getting very much vaporiztion. Lets say 5 psi per pound so 10 psi in the tank. Now if you have 15 pounds of Lp and at 5 psi your gonna have 75 psi in the tank.

This is a great reminder. Keep your tanks topped off for best results and if possible, keep them warm.

[Black_Bay]

Where's Hank Hill from Strickland Propane when you need him? He knows propane and propane accessories.

[kais24]

Don't forget to start your vehicle every couple of hours so when you're done fishing you can drive your non-vaporizing propane tank home.

[Squirtis]

I am not sure where you get the pressure per pound. The volume of the liquid in the tank doesn't add to the pressure of the gas above it. It's just Vapor Pressure, which is determined by the type of liquid/gas and the temperature of the liquid.

If you let your tank warm up to inside room temperature before you bring it out on the ice, it will give off more pressure, until the liquid in the tank hits the equilibrium point, which if the gas is flowing will be below the outside air temperature. The more Liquid you start with, the more heat that can be given off once the gas starts flowing to the heater, but after a couple of hours of use, or if it is a perm and the tank has been sitting there for a day at -10, then there isn't much hope for you. Larger surface area where the Liquid and Gas meet will mean for a faster boiling rate, but the pressure will stay the same, if the boiling rate can keep up with the flow to the heater.

Either way, my little Buddy heater is not going to keep my Guide very warm this weekend, so it's time to get the baby's room painted and wallpapered. Good luck and stay safe everybody.

Curtis

[harvey lee]

I dont know alot about the propane properties but I do know this, lets all be very careful out in these wicked cold temps this weekend.

[BobT]

Actually, liquid propane vaporizes at just above -44 degrees fahrenheit (-43.8 to be more precise).

Just like your car doesn't burn liquid gasoline and your fuel oil furnace doesn't burn liquid fuel oil, your propane heater does not burn liquid propane. It burns the gas or vaporized form of it. Unless the liquid is able to vaporize, it won't burn and your heater will not ignite.

Most solids, liquids, and gases expand as they get warmer. Contain it in a sealed container and heat it and it expands causing the interior pressure to rise. The pressure increase inhibits vaporization.

The warmer your LP tank gets, the more the liquid fuel expands and the higher the pressure inside the tank. Get it hot enough and the pressure will exceed the tanks breaking point and the tank will split. There actually is probably very little if any gas in the tank, only liquid.

You've probably seen the effects of this on your car engine cooling system. What happens if you open the radiator cap while it is hot? You get a high pressure blast of steam. The coolant was not in a vapor form while the cap was tight. If it was, the engine would have overheated. When you opened the cap you allowed the system pressure to drop and this allows the coolant to vaporize.

When you open the valve on your LP tank to supply your heater, you allow the pressure to drop and the fuel vaporizes as it escapes. This is the fuel your heater burns.

We are not even close to getting cold enough to cause a problem with your LP tanks. They'll work fine at -10 or -20 degrees F. You might start to have problems as the air temperature begins to reach -35 to -40 but except for north of about Hinckley, we haven't seen temperatures this cold since about 1997.

NOTE: wind chill has no effect on the LP fuel and it will not get colder than the air temperature.

Bob

edit: Wind chill can have one small effect on the fuel and the fuel tank. It can shorten the time it takes to cool the fuel down to the air temperature but it will not lower the fuel below the air temperature.

[sodajerk]

Propane vaporizes down to -44 degrees F. If it gets colder than that, it's no go with propane unless you heat the tank somehow.

The colder it gets, the less vapor pressure it has though, so on a colder day your heater may not put out the BTUs it does when the weather is warmer. It will help to shake the tank up now and then.

[metrojoe]

I know when I stayed up at a resort on Snowbank one year the owner said he had to keep his 100lb tanks half full or better when the temps got real cold or the heaters would go out. Whatever the reason it sounds like a good idea to top off the tank.

[Jeremy airjer W]

 Originally Posted By: kais24

Don't forget to start your vehicle every couple of hours so when you're done fishing you can drive your non-vaporizing propane tank home.

Another post worthy of "great replies of all time" Thank you kais, that was good for a chuckle!!

If nothing else keep it full so that you won't run out on the ice. Nothing worse then when the bite is on and the heater is out!!

[sodajerk]

 Originally Posted By: metrojoe

I know when I stayed up at a resort on Snowbank one year the owner said he had to keep his 100lb tanks half full or better when the temps got real cold or the heaters would go out. Whatever the reason it sounds like a good idea to top off the tank.

With large heaters that really pull a lot of gas out of the tank fast, it may be necessary to tie two, three or four 100lb tanks together to keep the vapor pressure up high enough to keep up with demand. The more tanks you have hooked up, the more surface area of liquid fuel you have exposed inside the tank, and more surface area exposed provides more vapor boiling off and feeding demand.

For smaller heaters used in fish shacks, one tank is plenty. The pressure in the tank is the same whether there is one pound or twenty pounds of propane liquid in the tank. The difference in pressure is caused by the outside temperature. The vapor pressure of propane at 0F is 28psi, and at 100F it is 190psi.

[BobT]

With more liquid in the tank the internal pressure will be higher because there's more fuel to evaporate. Put 1 cup of liquid petroleum in a 20 pound tank, heat the tank to above -44F and the fuel will boil into a gas state without problem because there is enough space inside the tank to handle it. Very little pressure is developed because there was room to expand.

Now place 1 gallon of liquid fuel in the same 20 gallon tank and when the tank is heated above -44F. it will boil but now there isn't enough room to allow full expansion and so the pressure builds. The fuel is now held in a kind of half liquid half gas state under pressure. When you open the valve it can complete the transformation as it escapes the tank.

Water is one of the few known substances that expands as it freezes. Fill a quart jar 1/4 full of water, seal it, and then freeaze it. The jar will not break because there was adequate space for the water to expand. The air in the jar will be compressed ans so there will be some pressure. Repeat the experiment but this time fill the jar full. It will break when the water freezes because there's not enough space inside the jar to handle the expansion and the jar is not able to withstand the pressure.

You don't have to be concerned about your tanks at these temperatures. Looking at our thermometer right now, it is

-21 degrees out there and our gas fireplace is working fine and the tank gauge indicates we are at 35%. Now if we were at

-41F I'd expect to have problems with the fireplace. Growing up on the iron range, it was common to experience temperatures low enough to create problems with propane but since I moved here to the tropics 18 years ago, the coldest I have ever seen is -36F. That was the day Tower set the all-time lowest recorded temperature in Minnesota at -60F in 1996 .

This reminds me. I thought I-Falls or Embarrass were supposed be the "ice box of the nation."

Bob

[Squirtis]

Bob,

This thread may never die, but I have to disagree with you. Sodajerk has it right. It all boils down to vapor pressure, which is directly related to temperature of the liquid in the tank. As he stated, Propane emits a lower vapor pressure at 0F than at 100F. As the temperature decreases, the vapor pressure drops, until at -44F, the pressure is 0psi, which will cause no flow of gas through your hose. The Propane is not in a quasi-vapor/liquid state, there is a definate distinction between the liquid inthe bottom and the gas at the top. I encourage you to do your own experiment and find out that your 1/4 full jar of water will in fact break, not because of air pressure, but the fact that as the water turns to ice and becomes solid, it expands in all directions, including in the direction of the sides of the jar, which will break it.

Going back to your cup versus gallon of propane, the only way this would be true is if the cup of propane would be able to fully boil into gas , and therefor, as the flow of gas goes to the heater, the pressure will drop. If you can maintain some liquid in your tank at all times, it will make no difference how full it is. When you open the tank, no matter how full it is, you will be flowing gas, unless the outlet is below the liquid surface.

Anyway, stay warm and safe this weekend.

Curtis

[harvey lee]

The real value to this post is thet RLF&Tackle is willing to fill partial tanks and not charge for a full fill. Thats a great offer.

[Kyle Sandberg]

That is a great offer. Its hard to find a store that is willing to take the extra time in this weather to do that. Thanks guys.

[sparcebag]

That is a great deal!! I look at it this way..I dont know if my tank is 1/2 full or 1/2 empty?? but if it does'nt put out fuel I'll fill it,then it fuels the heater.Thats what I care about.

And not payin for a fill when only 2 lbs or gals. are needed is a deal!

[BobT]

You are absolutely correct, Curtis. The pressure is directly related to the temperature. I have not disputed that and in fact that is precisely what I was saying. The pressure is a direct result of the expansion of the liquid and gas as its temperature rises. The higher the temperature the higher the pressure and vise versa.

I will agree on this point. The closer you get to the freezing point of -44 degrees the slower the vaporization process and the lower the pressure because the fuel, both the liquid and the gas, is contracting and this is lowering the pressure but not until the temperature gets down somewhere around -35 should there be any concern.

Where I am in disagreement is the spread of fear that our propane won't work if we have it outside at -10 degrees. Man if that were the case, there'd be a whole lot of people with frozen homes.

In reply to my cup vs gallon of propane - YES!! That is exactly what I was saying. When you start with a volume of liquid and then raise its temperature to some degree above its boiling point it will vaporize - so long as it has room to do so. If it does not have adequate space to do so, it will remain liquid and due to its expansion it will cause an increase in pressure against the container walls.

As far as the glass jar experiment. I have frozen liquids in glass jars.

Here. This is some information I found. Maybe this will help.

*************************************************************

Propane: When you purchase it, it's in a liquid state. Tank gets filled to 80%. Allows for 20% expansion. When vaporized, it expands 270 to 1. Liquid propane "boils" at -44F. If surrounding area is colder than that, it stays in liquid form, and won't come out of tank. Propane expands 1.5% for every 10 degree increase in temperature. *************************************************************

The 270:1 expansion rate is what causes the pressure to build. My cup vs gallon was inaccurate because a cup is not 1/270th of a gallon but my illustration was the same.

If you have a gallon of propane in a 20 gallon tank and heat it to above -44 degrees it will evaporate and expand. The gas will try to occupy 270 gallons of space but it can't because it is being squeezed into a 20 gallon tank. This causes pressure.

If you have an air compressor you are doing a similar thing by forcing a large volume of air into a small container and in doing so the pressure climbs. If you had a powerful enough compressor you could force enough air into the container to press it into a liquid state. You would have liquid atmosphere in your tank at ambient temperature until you opened a valve and allowed it to escape and when it did it would violently errupt into a boil and evaporate, similar to the blast of steam you get if you open a hot radiator cap.

Bob

[Macgyver55]

Don't forget to factor in that during cold weather, when unsed, your propane cylinders will only chill to the outside air temperature. Once you begin using propane, the evaporation of the liquid propane inside the cylinder chills it even more (below the ambient temperature) this can/will result in reducing the fuel pressure even more.

[boatfixer]

Correct. The boiling process of the liquid results in a rapid heat transfer. In other words, when a liquid is boiling, it is transfering heat from what ever source it is in contact with. If you have ever had propane hit your skin before, you will say that propane is cold right?. wrong. What you feel is the heat being rapidly tranfered from your skin to the liquid, during the boiling process. Same thing when you feel the tank after the heater has run awhile. Which brings up another point. Does the amount of liquid or tank size matter? Yes. The only way the liquid can transfer heat to boil, is to be in contact with the surface of the tank. More surface to liquid contact, more heat transfer, better boiling, better vaporization. The one thing nobody has mentioned yet is the amount of draw from your heater. Standing pressure in the tank is one thing, keeping up with the demand from your heater is another. If you dont believe this try running you homes heating system off a 20lb tank at the temps we have today. You would pull the vapor out of the tank so fast, the liquid couldn't keep up with the vaporization process. The heat would be pulled out of the tank surface faster than the outside temp could replace it. Once the heat transfer stops, so does the vaporization.

[boatfixer]

So, to get back to the original post, great idea and a very fair way to do business

[perch_destroyer]

This post reminds me of the old show "Mr. Wizard" when I was growing up, that was cool. What a lot of great information though, thanks to this thread, I now will check my heater before leaving to the lake.

[sparcebag]

Boat fixer sorry I have to disagree with the 20lb tank not runnin a house!! theres a regulator on the unit being heated well different story...Sooo my neighbor right now at -15 degrees is using my 3 20 lb tanks to heat their house till tomorrow when delivery isnt emergency.there workin just fine since this morn when it was -20.they borrowed a 100lb tank thats we guessed 1/2 full if my 20s dont make it till morn.Their usin one tank at a time not 3 inline.

[chris63]

Now go FISH!c63

[boatfixer]

I stand corrected. In some situations that is do-able. A few years back when I delivered the stuff, I did unhook a few 20 lbrs that the customer hooked up till we got there, more times than not though, the 20 lbr quit flowing, when it was dang cold. One big frost ball! I should have known that analogy would come back to get me.