MacCoupler revisited.

[howlinowl]

Well, I finally used up the last of the propane in my old 1lb bottle of propane, so I was able to refill it and compare the weight of it to a new one.

I weighed the bottles using my refrigeration scale.  It is a scale I use for my job to weigh refrigerants into systems after they have been repaired and evacuated.  We get refrigerants in large tanks, and if you need to weigh a pound in, you put the tank on the scale, purge the lines, zero the scale and start adding refrigerant.  It shows how much refrigerant has been transfered into the system.

Both bottles are Coleman, the only difference is that the new bottle still has the label on it.  

I weighed the new bottle.  Weight is: 1 lb. 14.7 oz.
I weighed the old bottle:  Weight is: 14.6 oz.

Differance is 1lb .1 oz.

I put the old bottle into the freezer (after I put it into a plastic bag, my wife scoulded me when she found it in there with the food) and went to bed.

This morning, I attached the MacCoupler to my new, full, Blue Rhino 20 Lb. propane tank (I believe they only have 17 lbs in them new, cause of the OPD).  Attached the bottle to the coupler, turned the tank upsidedown and open the valve.  Waited the 60 seconds they recommend (actually sounded like the pressure had equalized by 30 seconds, but that may vary depending on how full the tank is).  Closed the valve and removed the bottle.  

Used some Leak detector bubbles that I use to check for refrigerant leaks (it's like soap, maybe a bit thicker, blows up bubbles if there is a leak).  No leak found at the valve of the bottle.

I then weighed the newly filled old bottle:  Weight is:  1lb. 13.6 oz.

Only short an ounce compared to the new bottle.  Technically, it didn't fill it "all the way" but at an ounce is hardly a point to argue about.

Personally, I like the coupler.  Some have voiced opinions on whether they are safe.  I believe that if your bottles are in good shape, not real rusty, that the process is safe.  All you are doing is equalizing the pressures between the bottles.  If you were pumping LP into the bottle, I could see possibly over filling it.  But it isn't, just equalizing pressure.  

Some say the valve may leak.  Mine didn't, but since they recommend you check it, I would assume that it is a possibility.  If it did, I believe it would be a small leak.  Just keep the bottle outside, so the gas isn't able to accumulate into a hazard.  

I've taken pictures of the process, but I need to find a way to get them to my webserver.  Last time I've uploaded anything to it, was when my wife still lived in the Philippines.  Since then, I've networked the computers and her's is the "server" as cam feature didn't work when It was the "client" and she uses it to comunicate with family and friends in the Phils.  Now that mine is the "client", my FTP program doesn't work.  May be a configuration problem, but wasn't important enough for me to bother with.  I may have to install the FTP program on her 'puter and use it to transfer files.

Allan

[Old Goat]

Glad to see that your refillng operation was a success and like you say, an ounce less will never be noticed. I have been refilling the 1 lb. cylinders for a long time now and have never had a problem with leakage, not to say it does't happen...I always keep the plastic cap on the valve when not in use, also, if a tank starts to get rusty I toss it and buy a new one. Rerfilling sure saves a good buck if you use alot of them like I do in the winter camping season. I made a bin in the popup's front storage trunk that will hold six of them very snug and secure.....

[oldmoose]

Occassionally I get a bottle that has the valve stick. I have some wood bbq sticks nearby in case the valve sticks. I also do this out doors.

[Chief Redelk]

I fill small throw away  propane bottles from Walmart and havegreat success. We all know the trick is freeze the small bottle warm the 20 pound bottle, BUT I took that one step farther and I wish to share it with the group. My small bottle was wrapped in a wet towel placed inside a plastic bag and placed inside my freezer allowing the wet towel to make and ice covering on my bottle. My filler tool is the old type with a stem about 6 inches long between the two bottles so I wrapped wet tissue on that stem and froze the filler tool also. Of coures I kept, all of the moving parts and all openings clear of moisture.. While the small bottle was freezing the 20 pound bottle sat in the sun to heat. With the filler attached to the big bottle first, the valve slightly opened allowing a small bit of  gas to escape. This removed air from the filler valve before being attached to the small bottle. When both bottles were properly attached the valve on the big bottle was opened all the way. As the gas filled the smaller bottle it made a noticable sound. I did not time the event with a clock, I simply went by the sound of the gas pressure balancing out. When the sound stopped I waited for about 45 secconds then closed the valve on the big bottle. The little bottle was removed while the big bottle was still inverted.  That was to insure only vapor would escape from the little bottle. When a bottle is inverted liquid can come out but standing up only vapor escapes. The small bottle was wieghed and found to be properly filled. A good way to make a cheap home made scale for wieghing small bottles is to use a balance board. To do that I get a new bottle factory filled and remove the black plastic bottom. Using staples permanently attach the bottom to the end of a short board. A board measuring about 1.5 inches wide by .75 inches thick and about 24 inches long works well for me. The wieght of the board makes a lot of difference so you may need to experiement. Lightly set the new bottle back inside the plastic bottom making sure it does not stick so you can't get it back out without damage to the plastic bottom.  You do not want to remove that bottom. It has to stay with the board to insure all bottles sit exactly in the same place. Lay the board on the edge of your table with the bottle sitting at the tables edge. Gently slide the bottle over the edge of the table. The board should allow you to extend the bottle over the edge quiet a bit. Slowly move the bottle farther away from the table until the back edge of the board starts to lift off the table. The wieght of the bottle will immediately pull the bottle down once you go past the balance point, so be prepared to catch it. Move the board and the bottle back onto the table until you find the balance point. When properly balanced the bottle will hang over the the edge of the table without falling. If you try to get a LOT of daylight under your board the bottle will fall onto the floor. YOU MUST be careful doing this. When the Factory filled bottle finally balances make a permenant make on the board at the edge of the table on the board where it meets the tables edge. That is your balance point. Play with the factory filled bottle and repeat this procedure until you know exactly where the bottle will balance and feel confident with your balance board. NOW use a little bit of  propane out of the factory filled bottle and go back and check the balance point. You will see that this bottle needs more board extended over the table edge. It does not balance out where it did when full. It will balance slightly behind your first mark. Somewhere in between those two marks is where your refilled bottles should balance. When you re-fill a bottle, remove the black bottom of that bottom and  loosely set your bottle  in the black bottom attached to your balance board. This is to insure every bottle sits exactly where the new bottle sat when it was balanced.  If your refilled bottle balances anywhere between the two lines marked on your balance board,  it's properly filled. IF it balances in front of the front line it's probably over filled and way behind the back line means it's light. Check your balance board from time to time to make sure the wood has not changed or the wieght has not moved. To do this you can check it out everytime you get a new bottle. But unless it has changed a lot know that not all bottles are going to wiegh exactly the same... Hope this helps a lot . Chief.