Refilling 1 pound propane cylinders, steps and video

[Spudgunr]

Hey guys, this forum has had a recent rash of posts on refilling 1lb propane tanks, but I'm having trouble even finding the specific post I'm thinking about (had some pictures of the process). I'd love to give credit, though its really the SEVERAL of the posts mentioning it that got me to finally get this device. Due to recent weather there was a run on the little tanks here, and I realized their value. My wife did a great job in the practice run we did lighting the buddy heater. I have confidence she can change the small tanks, but I don't have so much confidence she can hook up the grill tank adapter and get it tight enough on her own. So, I decided to get the refill adapter so that I can refill the tanks I already have on hand. I keep 3 grill tanks on hand, so I can fill the small tanks several times if needed. The video that is embedded in the post was my first attempt. I failed once on accident, once on purpose, and succeeded on the 3rd try (I think I got out of order on the first run due to setting up the videos). Kind of a long video, but I think watching my failures will be more helpful than ONLY seeing a success.
So, here is what I have on the blog post:
Refilling 1lb propane tanks « A Handful of Tranquility

Recently amongst the various forums I browse I have seen several mentions of refilling 1lb propane tanks, so I thought I’d get in on the action. I have had hoses to convert between the tank types, but I hadn’t actually pickuped up a refill adapter. I picked up this Mr. Heater for around $14 on amazon, at least $5 cheaper than the hardware store had it for.
The video is of my first attempt. Now, even before my first try, I was confident that I would be successful, mostly due to the various hints I had read in some posts on various forums. I am quite familiar with PV=nRT, vapor pressures, etc due to my chemistry and chemical engineering degree. You do NOT need such information to be able to fill the tanks if you follow directions. So, here is the video:

[video=youtube;CAE5zXNnFMA]https://www.youtube.com/watch?v=CAE5zXNnFMA[/video]
So the steps are:

1. Have a FULL or nearly full grill tank available
2. Fully empty the disposable tank (the mistake I made) at room temperature or warmer until there is NO pressure left.
3. Freeze your tank for an hour or so. Make sure your grill/big tank is room temp or warmer
4. Weigh the small tank, and tare your scale (and DONT let it turn off or you lose your tare, another issue I had)
5. Screw in your adapter (left hand threads) to the grill tank and use a wrench or socket to tighten (it seems to be around 29mm or 1 1/8″)
6. Take 1lb tank out of freezer and screw in
7. TURN LARGE TANK UPSIDE DOWN and turn on the valve. Upside down is key, that is the only way to get liquid out.
8. Wait 1-2 minutes or until you stop hearing any sound, then turn the valve OFF on the large tank, then you can unscrew the small tank
9. Weigh and verify the small tank

Now, I have also read a few posts by people who have not been able to get their tanks full. Here are a few possible problems:

• OPD valves: They do NOT stop you from getting liquid out. There is a float that comes and blocks off the internal mechanism if the propane place tries to fill the tank too full. However, if you let your tank level get too LOW, then when you turn the tank upside down the OPD device will fall towards the valve. If there isn’t enough liquid inside to float it up to the bottom of the tank (since you have it upside down, up is the bottom of the tank) then gravity will pull it down towards the valve, shutting it off. So, for your first attempt use a FULL (or at least very close) 20lb tank, so you will know the process works.
• There is no difference in temperature. Your small tank has to be COLD, and your big tank has to be warmer. This is due with the vapor pressure of propane. At 75 degrees propane is at about 140 PSI. At 25 degrees it is at 60psi, and at 0 degrees it is at 40 psi. You need to put the small tank in the freezer and have the big tank at room temperature. I’ll nerd it up a bit at the end. Your grill tank doesn’t have to be cold when it gets filled because the filling station uses a pump to actually PUMP the liquid in, but we are relying on pressure to drive the liquid in. If your tank is empty the starting pressure will be 0, but as soon as liquid hits it it will flash the propane. We want it cold to keep the propane liquid and the pressure low, allowing more propane in.
• Its possible some people did not turn the big tank upside down. If you do not, then you will only equalize the pressure and get essentially no liquid. While there are ways you could work around that and turn the propane to liquid, they would be time consuming for sure. A 1lb tank is actually 16.4 ounces, basically making it an exact quart of liquid that it will hold when new. The inside is probably a bit over that, making it possible to over-fill the tank. So, if you fill this with only gas at room temperature you will only get about half an ounce (according to the ideal gas law… close enough). Its no wonder some people don’t think it works.
• Failure to empty the tank. I knew this before trying the filming, but I failed to ensure that it was fully empty. The liquid entering the tank has to compress the gas that is there (even at ambiant pressure, there is still SOME gas in there unles you pull a vaccuum). Even 15 psi reduces refill capacity by half! Whoops, it is a bit embarrasing to fail on camera (both with the failed fill and the scale error I had), but I think it works out for the best. The video will likely be more informative with some common errors thrown in. Emptying the tank when it is at room temperature or warmer is more effective than emptying it once it comes out of the freezer.

While I wasn’t successful on my first attempt, I hope you can learn from my mistakes. I got 5 ounces when I purposely used a warm tank, I got 6 ounces when I seem to have not fully emptied the tank, and 14.5 when I followed the steps I outlined.


Refilling 1lb propane tanks « A Handful of Tranquility

 

[Spudgunr]

I posted this here because I think it deserves a separate topic. My apologies if it has been covered, I tried searching specifically for the posts I alluded to, I found a couple but not others. Its possible they were from different forums, so I wanted to make SURE the knowledge was here as well in its own dedicated thread. The video is a bit slow, I realize, but it covered 3 fillings and some of the errors I had. If you have feedback, please don't be shy, I have already changed the (blog) post a few times based on feedback from the thread I started at arfcom. I just ask that you be clear about negative feedback so I know how to improve this post or future posts.

This is the entire blog post copied over, I will try to keep this page updated with any changes made to the blog, and vice versa.

 

[Dorky_D]

I have a Mr. Heater Big Buddy. I found a hose that will convert from the larger tank straight to the heater.

 

[Spudgunr]

I also have a hose that converts, but am not confident in my wifes ability to use it. I posted this on another forum as well where a guy was in your situation. So next time I was at the hardware store I checked out the big buddy. It has a quick disconnect that looks awesome. However, my portable buddy does not have that quick release adapter, it only has the 1lb tank threads. The hose I have has about a 1" knurled nut at the end, that is the part I don't think my wife could get tight enough comfortably. I picked my portable buddy up on clearance for $40 a few years back, but if I were in the position to buy one at full price (or if the big buddy were available on clearance as well), I would definitely get the big buddy system. I may still in the future, but with the ability to refill the tanks I think I now have that need met for now. I do also like the small size of the portable buddy, so I can see the merit in having both.

I also like that there are screw mounts on the back. Can you measure the spacing on your big buddy to see what the hole spacing is on the back? On the portable buddy its only around 12", if I were going to mount this to the wall I would put a board up screwed to the studs and then have screws with the proper heater spacing on there. It would be convenient if the big buddy already had 16.5" spacing.

 

[snorko]

My understanding was the newer tanks with the "improved" safety valves could not do this. Can anyone confirm?

 

[Spudgunr]

I did it in the video with an OPD tank. When they get low (1/4 full or so) the float in them can shut off flow when turned upside down (which is why step 1 is to have a full or nearly full, so that the person trying it will know it works). You should get 10 or more fills from a tank, and then the rest can be used on the grill, or other tank heaters.

Normally the float is floating up. When getting over-full it floats up and blocks off the valve. When turning upside down it floats up (to the bottom of the tank). When getting empty enough is sticking out of the remaining liquid that gravity pulls it down and not enough liquid is there to let it float up. So yes, it can mess up the process if there is very little liquid, otherwise it isn't a real issue (though I do remember hearing when they first came out that it would prevent liquid at all).