Refilling one pound propane bottles

[harris155]

https://www.amazon.com/only-fire-Pro...39651381&psc=1

[Unplanned Tourist]

Originally Posted by JMSCTB

To the original post:
Where did you get that adapter?
I need one, but don't know what to search for.

I got it from Amazon.ca $18.00 (That's Canadian $, so probably around $14.00 US) for the filler and 4 brass caps. It works great.

Pays for itself with 3 fillups.

https://www.amazon.ca/dp/B095K1XWJ6?...roduct_details

[Unplanned Tourist]

Originally Posted by BobGed

That sounds like a great exchange program.

Very nice car. Did you build it?

Actually Ford built it in September 1927. I just modified it a little bit.

[garywilson]

Originally Posted by reubenray

A little of topic. but here goes.

Is there a way to fill up my 20lb tank from a 100lb tank?

You need a tank with a 'wet line'. I don't know that you can get a 100 lb with one...

[theoldwizard]

Originally Posted by garywilson

You need a tank with a 'wet line'. I don't know that you can get a 100 lb with one...

No you do not !

Post #63

Originally Posted by theoldwizard

Much to complicated ! All you really need is different pressures which can easily be achieved with different temperatures !

Place the larger cylinder in strong sun light. Place the receiving cylinder in the shade. Better yet, in a container of ice water. Let temperatures stabilize. (30 min?). Connect hose open valves. Open the bleed valve on receiving cylinder. Pouring hot water over the larger cylinder helps. Fill time depends on the size of the smaller cylinder and the temperature difference.

Works for "disposable" cylinder too. The bleed valve is opened by pull the needle out with needle nose pliers or a hemostat.

[hednout]

Originally Posted by theoldwizard

No you do not !

Post #63

That is a proclamation, not an explanation.

The latter would be helpful.

My suspicion is that that the idea is that in the large the container the sun will vaporize propane on the side facing the sun faster than it condenses on the side facing away from the sun, with that propane vapor being conveyed to the smaller and cooler container, where it will condense back to liquid propane.

To get the pressure differential you have opened the bleed valve on the smaller container. That will create a pressure differential- but primarily between the smaller tank and the atmosphere. The vapor in the small tank only has to travel from the liquid surface to the relief valve. The vapor from the larger tank has to travel through that tanks valve, then through the tubing, and then through the small tanks valve and then into the small tank. Your blowing off vaporized propane from the smaller tank will further cool it as the propane in the smaller tank vaporizes. At some point the partial pressure in the small tank drops low enough that the vapor flow from the larger tank increases- and some of it may condense into liquid propane in the small tank- but it will also be venting out the relief valve you have open.


While you may get some propane transferred to the smaller tank, it seems like most of it is transferring to the atmosphere.

What am I missing?

[Unplanned Tourist]

Originally Posted by hednout

That is a proclamation, not an explanation.

The latter would be helpful.

My suspicion is that that the idea is that in the large the container the sun will vaporize propane on the side facing the sun faster than it condenses on the side facing away from the sun, with that propane vapor being conveyed to the smaller and cooler container, where it will condense back to liquid propane.

To get the pressure differential you have opened the bleed valve on the smaller container. That will create a pressure differential- but primarily between the smaller tank and the atmosphere. The vapor in the small tank only has to travel from the liquid surface to the relief valve. The vapor from the larger tank has to travel through that tanks valve, then through the tubing, and then through the small tanks valve and then into the small tank. Your blowing off vaporized propane from the smaller tank will further cool it as the propane in the smaller tank vaporizes. At some point the partial pressure in the small tank drops low enough that the vapor flow from the larger tank increases- and some of it may condense into liquid propane in the small tank- but it will also be venting out the relief valve you have open.


While you may get some propane transferred to the smaller tank, it seems like most of it is transferring to the atmosphere.

What am I missing?

I believe you are quite right there. You would be much farther ahead by turning the 100 pounder upside down and getting liquid propane transferring to the 20 pounder. A little awkward to say the least.

[Ray,IN]

Originally Posted by SqueakyWheel

I do. If you put the bottle in the freezer for an hour after the first shot, you can get it full on the 2nd shot.

At what temperature does propane change from a gas to a liquid, is your freezer even close to that temperature?

[rarebear.nm]

Originally Posted by Ray,IN

At what temperature does propane change from a gas to a liquid, is your freezer even close to that temperature?

Propane vapor changes state at -43.6F. No home freezer comes close.


I can fill a FlameKing bottle in about two minutes, no waiting around for cooling once or twice. I get a properly filled bottle in one shot and done. I have seven of those bottles now, so I usually wait until I have four or so empties and do it all in one setup.

[Stevens10]

[QUOTE=rarebear.nm;6455625]Propane vapor changes state at -43.6F. No home freezer comes close.


That is at atmospheric pressure. LP in a tank reaches a pressure based on its temperature, that is why if you connect a tank in the hot sun with a tank in the shade eventually the tank in the shade will be full of liquid. The higher temperature of the sunny tank causes a higher pressure, this high pressure gas migrates to the cooler tank and condenses since the pressure in the system is higher than the vapor pressure of the cooler tank. No need to vent the cooler tank that just wastes propane. the difficult part of this is determining when the cooler tank is at 80% full, but the modern 20 LB tanks do have a float valve that prevents over filling so you should be good to go.

[theoldwizard]

[QUOTE=Stevens10;6455693]

Originally Posted by rarebear.nm

Propane vapor changes state at -43.6F.

Which is why you can get propane vapor out of a tank at even 0F !

Originally Posted by Stevens10

No need to vent the cooler tank that just wastes propane. the difficult part of this is determining when the cooler tank is at 80% full, ...

What is with the 80% statement ? All D.O.T. approved tanks are designed to be filled until liquid come out of the vent.

[hednout]

Stevens10

You said "eventually". How long would this take?

I understand the physics- but would it happen at a rate that would make it useful?

My trailer has the propane tanks on the tongue. In the summer we would be running the rooftop AC on electricity, the water heater and refrigerator on electricity. The propane lines are in the shade, and eventually lead up into the air conditioned trailer in the kitchen at the back of the RV. Those lines should
gradually fill with liquid propane from condensation if the rate on condensation is significant. When we do use the stove in the kitchen, we do not have liquid propane come out the burners. Is there some mechanism to prevent this?

To take it further- connect a full 100 lb tank to an empty 100 lb tank with both valves open. Both tanks get the same amount of sunlight. At night the empty tank will cool faster than the larger tank, so should start to fill with propane- but then the next day will warm more quickly and transfer at least part of it back. --But thinking further- perhaps not. In the nearly empty tank the sun hitting the side of the tank is warming vapor on that side of the tank. The warmer vapor be at the top will rise in the tank and be at the top, with the cooler valor below. The bottom of the tank curves in and will not heat as quickly as the vertical sides. The liquid propane in the bottom of the small tank is in the cooler part of the tank. In the full tank the sun will be mostly warming liquid propane, with less vapor to heat...... Lots of variables to consider and not enough time... My initial thought is that eventually each tank is equally full, if the sunlight they get is equal. What do you think?

[hednout]

On further thought-- There will be a pressure difference between the tanks for a very short time right after the valves are open. After that the pressures will be essentially equal.

Why? The connecting hoses we have are sized so the tanks can supply multiple appliances running at the same time. Unless the hoses are unusually small or very long the pressures should be very close. Because the tanks are purged of air on the first filling it is 100% propane vapor, so this should not affect the rate of condensation.

FYI If you are ever in a situation where you have to breathe through a tube, either inhale only or exhale only. If you try and do both you breathe in the air you just exhaled and depleted of oxygen. Learned this as a kid with a garden hose. Also- do not try and go under water and try and breathe through that hose. The water pressure immediately forces the air in your lungs out, you cannot expand your chest to take a breath. There is a reason you do not see snorkels with 3 foot tubes. If you are deep enough the water pressure will be wanting to push your lungs and the rest of your insides up the tube.

[rarebear.nm]

[QUOTE=Stevens10;6455693]

Originally Posted by rarebear.nm

Propane vapor changes state at -43.6F. No home freezer comes close.


That is at atmospheric pressure. LP in a tank reaches a pressure based on its temperature, that is why if you connect a tank in the hot sun with a tank in the shade eventually the tank in the shade will be full of liquid. The higher temperature of the sunny tank causes a higher pressure, this high pressure gas migrates to the cooler tank and condenses since the pressure in the system is higher than the vapor pressure of the cooler tank. No need to vent the cooler tank that just wastes propane. the difficult part of this is determining when the cooler tank is at 80% full, but the modern 20 LB tanks do have a float valve that prevents over filling so you should be good to go.

I prefer the refilling method Flameking uses. Invert the 20 lb cyclinder, attach the pipe setup and attach the 1# bottle. Turn on the valves and when gas starts to vent turnoff the valve. Yes you have to operate a venting valve. Just like getting a larger cylinder filled. Fast, simple and no need to wait for sunshine and arrange for a sunny/shading area to work. The transfer process is moving liquid not gaseous propane.


At typical room temperatures propane will stay liquid at about 100+ PSI. A propane cylinder is around 100 to 200 PSI. With some free head space, expansion space, at the top of the cylinder some propane vapor will fill that space.



For the question why we don't see liquid propane at our stoves etc, is that the regulators reduces the pressure to about 11 WCI or 0.3PSI. Well below the pressure required to maintain liquid propane at room temperature.



Taken from a propane vapor pressure chart: At 70F - 100 PSI; at 30F - 53 PSI; at 0F - 25 PSI; at -20F - 12 PSI. As the PSI drops so does the volume of vapor production which limits the BTU output from the cylinder. This is why it becomes harder to run multiple propane devices at colder temperatures. This why folks who winter camp in a tent will sleep with their fuel bottles so they can light them in the morning. I've done this many times when temperatures were 0 to -20F.



So yes given enough time and maintaining a supply and target tanks in hotter and cooler positions propane vapor will refill the cooler cylinder. If you want to fuss with it that much.