My first bottle of propane 5 gal (20 pounds ??) is down so my manifold pressure is less than 5 psi. I need at least 8 psi at my altitude, 9 is okay and 10 is great. The bottle still sloshes alot and the freeze area is about 2 inches up from the bottom. I am planning to buy my second bottle, keeping the first, and when the second is in the same condition as my first one now is, I plan to invert it and heat it and push is liquid into my first bottle. After doing this about
15 times, I think I will have saved myself the cost of a bottle of propane. Are there any other better tricks to conserve that liquid that remains in the tank? I already allowed the first bottle to heat in the sun, but the manifold pressure went from 10 psi to 4 psi almost within a minute.
Put a drop light next to it to prevent it from freezing. Better yet :
Or it in a bucket of water. Freezing makes liquid and keeps the pressure low. It normally regulates itself by dumping to liquid if the pressure is high.
A bucket of water - such that it doesn't freeze - will heat it enough and build pressure.
Mart> My first bottle of propane 5 gal (20 pounds ??) is down so my manifold
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If you manifold the smaller tanks together they will act as one larger tank in terms of pressure delivery. The amout of liquid surface area has a lot to do with how quickly you can draw off vapor without freezeing. This combined with the droplight or a water bath could save you the hassels of transfering propane from one to the other. One other thing , the place I get my propane charges me by the gallon so I only pay for what they put in the tank ie: no waste.
It isn't the amount of gas left as it is rate of use vs change of rate rate. You not longer have enough liquid to generate gas as fast as you are using it. Gasifying faster would help. I've seen tanks set in buckets of warm water. Manifolding tanks together would also help.
Try two electric heating pads wrapped around the bottle and held in place with bungee cords. We've used a similar technique for nitrous tanks and it works very well. No risk of overheating either.
(I hope this table comes through okay. -40 degrees should read 3.6 psi and 110 degrees should read 220 psi. I would have sent a graph, but I don't think the newgroup can handle pictures.)
I use a rubber hog waterer with about 2 inches of water in the bottom and put the tank in it. As long as that water doesn't freeze, you've got at least 60 psi on the high side of the regulator.
Dont' try the thing with emptying one bottle into another. It probably won't work anyway with OPD valves on today's tanks. I guarantee that you WILL get all the liquid out of the tank if you keep the temp up. The liquid keeps gassing off inside the tank at the pressures the chart shows, so you will have a short period of time where you still have full pressure for the temp as the last bit of liquid turns to a gas. Then you get a rapid drop and you are "out".
Add a 250 psi gage to the input side of your regulator and you will see all this happen.
I would get a second tank anyway, so I don't run out in the middle of a job.
One thing to think about the problem. When the new tanks were sent out there was some gas stored within. Sometimes liquid gets in and a customer that I knew in CA several years ago - had some in there. The gas vendor didn't put in a open hose and dump (up side down) the junk out of the tank before filling.
So this might be the issue if heating the tank to get pressure doesn't work. Cut the columns out below and put into a spreadsheet - highlight and go to charts...
Mart> Here's what is going on:
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I did produce an Excel chart but I don't think the newsgroup supports pictures. I looked for charts on the web to reference, but since the only ones I could find were in Kpa or atmospheres and °C, I went with a table instead. Whenever I bring my gas forge to a demo or conference, I also bring a flip chart the has that chart, a table of propane facts, Safety considerations, and the instructions for making that gas forge. I put the propane bottle on a scale, weigh it at the beginning of the day and them again several times during the day to show actual propane usage. I also bring the hog waterer I mentioned so all see how the pressure is kept up, moving from scale to water as needed.
Just talked at length to the propane service guy today since he was here testing our whole system for leaks, proper valving, etc.. He drove up the driveway as I was starting to reply to this post!!!
He says that new tanks have only air in them, if anything. It would cost them extra to put anything in there. He said that, unless the new tank is under an actual vacuum (not likely when you buy from cheap places according to him) when you get it, you have to purge the air out before filling. Quite a process, according to him. They have to add a little propane, exhaust all pressure, then do that four more times, for a total of 5 times before filling! Total surprise to me, and I doubt that most fillers do it anyway.
As I recall the guy had some oil - a thin type. It shook like a 1/4 full bottle but would not fill as heavy. It put a spot on the ground. Maybe the place that made them had a compressor failure and it blew oil into the lines when pressuring the tanks. I can't figure anything else out.
This was one of the new OPT or whatever they call them. First version.
Martin
Mart> I did produce an Excel chart but I don't think the newsgroup supports
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I used to own a welding supply distributorship that also sold propane. I still have the license.
That guy was jerking you around. Either he didn't know any better or he was trying to set you up for an extra charge if you bring him a new tank to fill. Almost all small tanks now come filled with dry nitrogen. Some come with propane at atmospheric pressure in them. Those typically have a "purged" sticker on the valve handle.
Purging a portable tank at the minimum requires nothing extra. Simply open the 20% valve while filling. Air or nitrogen is non-condensable so it will be discharged rapidly as the propane level rises. Some guys pressurize and purge the tank once but my testing showed not even that to be necessary. Simply letting the 20% valve spew while filling lets all the air out.
It's easy to check. Simply measure the tank's pressure and temperature and compare it to a vapor pressure chart. Propane is a great refrigerant so vapor pressure charts are widely available. Here's one
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Measure the tank's temperature, look up the equivalent pressure in the table and compare it to the gauge's reading (a 200 psi gauge attached to a propane nipple works fine.) If the pressure is HIGHER then there are non-condensables in the vapor space. Easy enough to get rid of. Simply purge the tank for a few seconds. People cursed with those infernal OPD valves will have to attach a nipple to the valve to get any flow.
A little air in the tank doesn't hurt anything. It can't explode - it's far too rich. It'll make the fire act like it is a little lean for a few minutes until the air is purged.
If the pressure is a bit LOWER than the chart indicates, don't panic. That just means that the LP has some butane in it. It's still perfectly good fuel gas.
John
-- John De Armond See my website for my current email address
You can until the tank is almost empty. When the tank is full and inverted, the OPD float tries to float to the bottom of the tank and thus remains open. When the level drops to about the 20% level, the float starts rising toward the valve and eventually shuts off.
Assuming you own your tank and aren't swapping it at the local C-store, the best thing you can do is, before it is ever filled the first time, unscrew the valve from the tank and unscrew the OPD gadget from the bottom of the valve. It simply screws into the bottom of the valve with about a 1/4" NPT thread.
That one step eliminates the cursed valve and the flow restriction.
Interestingly enough, I've yet to encounter an OPD valve that actually closes off when the float rises. The flow is restricted but not turned off. Thus, the supposed justification for the damned things - to keep the bored and distracted filling attendant from over-filling the tank - isn't there. Worse, it instills a false sense of security. I've had more than one attendant tell me that he doesn't bother with scales or the 20% valve anymore. He just turns the pump on and lets it pump away until it 'stops'. That is, until the tank is solid with liquid.
Like most government meddling, the unintended consequences have negated any alleged benefit that might have accrued. And again characteristic of government meddling, they'd never in a million years admit to making a mistake.
The easiest way to get around the flow restriction if you can handle the weight is the 100 lb tank. It doesn't have to have an OPD and none do.
Another technique is to buy or have a gas company install a 250 or 500 gallon tank with a "wet leg". This is a fitting on the tank that has a dip tube. It is designed to empty tanks before moving them. With a few fittings, though, it can be equipped with a valve and hose. One can feed a high BTU burner directly from the wet leg or he can use it to fill smaller tanks.
Until I retired, I had a 500 gallon tank at my restaurant with a wet leg on it. I filled my 20 and 30 lb bottles that I used for catering and I filled the tank on my motorhome. I don't have a need for and wouldn't want to pay for having that large a tank filled now so I use 100 lb tanks as my bulk tanks. I fill my 20 and 30 lb tanks that still have the old style valves using a simple siphon method. No pump is needed.
This my page on filling throw-away tanks
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I made the page when I still had my bulk tank. Nowadays a 100 lb tank replaces the 30 pound one shown in the photo and 20 and 30 lb tanks fit the same hose with an adapter. The gravity head really isn't necessary. If the receiving tank's 20% valve is open, the difference in pressure will push the liquid propane. It can even push it a little bit up hill.
The advantage of the 100 lb tank is that it is the smallest tank that most dealers charge by the gallon instead of fixed fees. For the smaller tanks, labor costs are such a large portion of the sale price that a fixed fee is necessary even if the tank is only half empty. Generally, with a 100 lb tank, they'll charge you their per-gallon price.
If you find that you're filling the 100 lb tank more often than maybe once a month then you'd be better off with a bulk tank. You can book a year's supply in the summer when the price is the lowest. Last year the advanced booking price from my local dealer was 50 cents a gallon lower than the winter price. It was $2 a gallon advanced booking and $2.50 for winter fillings.
It's gonna be crazy this year, as they quoted the advanced booking price back in July at $2.79/gal. Like last year, I'm going to lay in a bit more firewood and leave the bulk tank empty. I have 2 100 lb tanks for emergency backup but I'll not be using any propane on a regular basis this year.
John
-- John De Armond See my website for my current email address
A supposed factoid is that the Compressed Gas and/or the NFPA people who instituted the OPD requirement don't tell anyone that they left a loophole: It's legal to fill a non-OPD tank of less than 40-pound capacity as long as that tank is marked "Industrial Use Only."
Thanks for the warning on that one! :) I'll watch 'em. :)
Ex C-Sapn junky here. :) I just plain ol' had to stop watching the crap it was too dangged irritating. :/
Thanks for the well thought out and well written answers! :)
Cool page, I already have a bottle filler, just haven't used it in years. :) And I have one old tank and one new OPD tank so I'm setup pretty good for my limited use of propane.
Was re-reading you instructions and wanted to share my method of refilling the "throw-aways"...
Instead of weighing them, I use the "slosh method". :) When the bottle feels like it's a little over half full I call it good. :)
Plumb-full bottles are a pain to use with one of those solid screw-on torch-heads (most of the time, IME) so why bother filling it more than 2/3s full? :)
Yep, that'll work for that kind of use. My use is a little different and I need every cc of fluid. One of my major uses is to replace refillable tanks. This notion popped into my head when I took a year off to see the country and get paid for it, that is, driving a semi rig over the road. Here's what got me started on this gig
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Before hitting the road I'd been in the restaurant business for about 10 years. I realized that for years I'd dragged out 20 and 30 lb propane bottles to power portable steam tables and the like, only to drag back home most of the propane. As trustworthy employees became harder and harder to find, I found yours truly doing more and more of the grunt work. That's the major reason that I sold out.
Anyway, I love food service so after I retired, I continued doing occasional catering jobs. Now I'd be lugging out ALL the equipment by myself. I did a time and motion study. One major heavy item that I eliminated was the refillable propane tank. Initially I bought some 5 lb mini-tanks but I quickly realized that if the tank ran empty, I'd have no recourse unless I happened to have thought to toss in another tank. Plus they're more expensive than 20 lb tanks.
My solution was to make up a tank "spider" to use disposable tanks. I used one of the 6-way aluminum air line multi-outlet devices made out of a disc of billet aluminum that Northern Tool sells. Visualize this assembly
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With the ell screwed into the disc and the valve on the vertical side of the ell, connected to the disposable cylinder adapter. There are provisions for 5 cylinders. The female POL fitting (so I can screw in a standard regulator) screws into the 6th hole. Five cylinders will power my gas steam table for most of a day and will power a high BTU burner for shrimp boils and turkey fries for quite some time if the assembly is put in a bucket of water to supply more heat of vaporization.
I package disposable cylinders in boxes that hold 5. They're light weight and easy to handle. I usually toss 3 or 4 boxes in the truck, though I've never used more than 2 sets of cylinders.
I save up batches of empty cylinders and refill them all at once. They go in a chest freezer until they're nice and frigid. I learned that, using the hose assembly shown on my refiller page, if I hold the cylinder upside down, liquid directly fills the tank without vaporizing in the gas space which quickly raises the temperature and slows the filling.
With a freezer-chilled cylinder, especially if it still has a little liquid in it, I can fill a tank in under a minute. I no longer need to weight the cylinder. I can listen and tell when the liquid is near the top (actual bottom) of the tank. I do check-weigh each one afterward and occasionally I have to blow off a little liquid using my tank drainer. I keep a chilled cylinder nearby for that purpose.
The only downside is that purchasing all the parts at retail makes the assembly quite expensive. I'm thinking about having a larger disc made at e-machineshop or a local shop that is large enough in diameter that the elbow won't be necessary. The threaded holes would be on the face of the disc around the periphery instead of on the rim. If I can figure out how to fit a check-valve in each hole, I can dispense with the valves. This might turn into a product :-)
This same approach might be handy for 'smiths doing demos using small propane forges. Especially if you're like me and have a back problem that precludes lifting more than about 20 lbs. If you don't use a full 20 lb tank during the demo then you're a candidate for this approach.
Oh, the other benefit. If I manage to forget spare tanks or I use more than I planned, I can run out to almost any store and buy more cylinders. It'll be expensive but at least I can get the job done. Probably no more expensive than those C-store cylinder exchanges.
John
-- John De Armond See my website for my current email address
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