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How to completely refill a 1lb "disposable" propane Bottle
Wow, Pchem, I appreciate the response! I had not considered the concept of H-bonding making water a particularly volumetrically stable state. Instead, I was mostly basing on my experience reading about metal molding and that the pouring at X degrees C vs (X+100) degrees C usually won't make a meaningful difference in volume contraction (it's all in the phase change.) That said, the liquid of metals would have a lot more effective bonding. (by the way, just to clarify, when pouring metals usually the mold is 1-3% larger than your desired object due to the metal contracting as it solidifies. Also because there's often a lot of surface finishing to do.)When I wrote my initial comments I had been attempting to find data for the expansion of propane with temperature. The only data I remember finding was between a small celsius range, (like 20C and 30C maybe?) and so the error in the posted numbers could have been all I was seeing. I wish I had found the coefficient of expansion that you found. Because whatever I found suggested much less of an expansion. I also went down a couple other lines that were just nonsense and I sort of wish I could edit or delete without obscuring the line of comments. That may be partly where you're confused by my data presented. I think your analysis is very cool and I appreciate it. I do wonder if the significance of 9% would go down if you in turn also counted the expansion of the tank dimensions itself, but maybe that would be very insignificant as previously mentioned, the metal inter-phase does not have meaningful expansion at this scale.
I've read a few of your comments and I'd say nice job sticking with the facts on the saturated liquid-vapor lines of reasoning. I don't quite understand the data presented in your post here. You might be underestimating the amount by which liquid propane expands with temperature. We get accustom to water, for example, but without the hydrogen bonding to hold it back, liquid propane expands considerably more easily than our experiences with water. From one source, the coefficient of thermal expansion for liquid propane is about 0.00155 / C. So, if a tank is filled on the coldest of days (-20C) here in the midwest, then on the hottest of days (40C) the liquid propane will have expanded by about 9%. If the original liquid volume was about 90% of the tank volume, it would now be about 98%. Of course, things could get worse in the trunk of a car on that hot day. To leave a "public safety" size margin for error, it seems the industry aims for 80% fill level. I think this is what dmmartindale was pointing out as well. High liquid levels may also make it more likely that if some over-pressure condition forces the relief valve open, that liquid propane (now at a boil due to the dropping pressure) might get forced through the relief valve - releasing a truly unexpected volume of propane vapor that might reach a more distant ignition source or displace O2 in some confined space .I also came across information that the pressure relief valve typically is calibrated to open at an internal pressure of about 375 psi. For saturated liquid-vapor in the tank, this pressure would occur at about 75C (165F). So much for carelessly transporting propane tanks in a closed car.here is the source for the coefficient (thanks google): http://abiquim.org.br/congresso/cong_cd/fullpapers...
i just ordered everything i need from amazon. my local stores don't have all the parts I need. - stephen.yawii
use a scale. weigh a factory filled tank, weigh the empty one, and weigh the one you filled. just don't put in more than 16 oz. - stephen.yawii
I use a very similar method to refill 1 lb bottles... right angle valve for decanting and forceps to open relief valve. Using this method its quite easy to overfill bottles and I see a lot of talk about how much to fill/overfill a bottle.I have a very simple rule of thumb. I weighed a bottle when I bought it. It was 880 grams (31oz). (I'm from Australia and we've used metric for the last 30 years). When I refill a bottle, I weigh it. If its close to (but not over) 880grams, then its fine. I put back on the cap and its ready to use. If it weighs more than 880g I bleed off* some of the liquid until its close to but under 880g. Job done.In short, I bring them to the weight of a new bottle, a little less but certainly not more.* If the valve is up, you are only going to bleed off gas. With the bottle up-ended and the valve pointing down, you will bleed of liquid, which has all the weight - gri2a
*they're only about 80% full.
As long as *there is some space.
Looks like a great valve set up- and it will work PERFECT with LEGALLY refilllable 1Lb Flameking cylinders that you can find at www.propane-refill.com .People- STOP messing with the safety features built into a single-use disposable (read that - do not refill) propane cylinders. We have the answer- Just not many folks know they exist yet! Our cylinders eliminate the problems and make it safer and legal to refill at home from your BBQ tank. The refill valve set up in this instructable will do the job perfect- it would maybe be a tad better if the fill valve was spring loaded so as soon as you let go it stops. (for safety) I included a photo of mine (not for sale).Happy to talk to you all from my website above!
I'm a gas fitter and propane tech, don't fill past 80%. They came up with that number when engineers filled a tank to 90% and then raised the temperature half a degree. The psi went from 125 to over 400. The empty space is needed to buffer the expansion. Or else you get the 'can of beans in the fire' except with propane instead of tasty beans.
In regard to the pressure relief valve and using an angled needle nose pliers to vent the 1lbers .... the LP can create an "icing" on the valve seating ring - if the valve doesn't re-seat try a little room temp water ....
Besides being very dangerous, what you all are doing is not legal. These cylinders are just that disposable. The U.S. Department of Transportation and your local building codes to some extent do not allow the refilling of these cylinders. READ THE LABEL. There are REFILLABLE cylinders that are available and safe. Manchester Tank makes one. Don't take take a chance on severely injuring yourself.
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