How much refrigerant is left unutilized in exhausted 30 lbs cylinder?

[ICanHas]

Since gas fills the entire volume of container, I need to figure out the water capacity of the tank.

I think I can pull down to 25m torrs, weigh it, then let it fill up with air and weigh again..or suck it up full of water and weigh.

It looks like air weighs 1.28g per liter and my analytical balance would resolve to 0.01g, so I think I can get a fairly accurate measurement...

Then I just have to calculate whatever the vapor density is at 90psia (75pisg) for HCFC-22 and CFC-12.

How illegal would it be to say take 15 cylinders that's down to 75psi and consolidate them into one using the recovery machine?

I know refilling disposable cylinders isn't exactly kosher, but then you can buy this attachment at Harbor Freight for filling 1 lb propane bottle from barbecue tank.

As long as you're reasonable with it and don't let it sit around for ten years I don't see a big danger in it.


The real question is, when they say "net weight 30 lbs" how much of the 30 lbs is usable? I've read that on tooth paste and such, the net weight only accounts for what you can push out. So, if you were to weigh a new toothpaste, empty, cut, wash, rinse and reweigh, the difference is more than net weight stated.

When R12 is at what it costs now, there's no sense in not recovering what you can.

I suppose you could even chill one of the empty cylinders on dry ice, then suck in the contents from other cylinders so as not to introduce nastiness from contamination in recovery equipment.

From icemeister's calculation, you're looking at about one full small can of refrigerant.

I know that R22 and R12 cylinders look the same size but R22 is 1.21(11.26 liter @ 20C full) and R12 is 1.33(10.25 liter @ 20C full) specific gravity, so, if they're indeed the same tank physically, "how full" depends on each refrigerant. finding the water capacity of the tank would be useful.

[garyed]

I have 0 left in my cylinders.
When my can goes near empty I just close the high side port & let the system pump down. It will suck every drop out of the can.

[icemeister]

Since gas fills the entire volume of container, I need to figure out the water capacity of the tank.

I think I can pull down to 25m torrs, weigh it, then let it fill up with air and weigh again..or suck it up full of water and weigh.

It looks like air weighs 1.28g per liter and my analytical balance would resolve to 0.01g, so I think I can get a fairly accurate measurement...

You really don't need to do all that. I used the concept of calculating the volume of 30 lbs of R22 liquid and divided it by 80%...which is roughly how much the tanks are filled with liquid.

Then I just have to calculate whatever the vapor density is at 90psia (75pisg) for HCFC-22 and CFC-12.

I did that from the ASHRAE tables. See my calculations.

How illegal would it be to say take 15 cylinders that's down to 75psi and consolidate them into one using the recovery machine?

It's all virgin refrigerant, so there's no EPA issues with recovering and selling it, as long as you don't mix it with some used gas.

The real question is, when they say "net weight 30 lbs" how much of the 30 lbs is usable? I've read that on tooth paste and such, the net weight only accounts for what you can push out. So, if you were to weigh a new toothpaste, empty, cut, wash, rinse and reweigh, the difference is more than net weight stated.

Net weight is what is actually in the tank. How low you recover determines how much you can get out. My calcs show that recovery to 15" Hg left less than an ounce.

[mark beiser]

I have 0 left in my cylinders.
When my can goes near empty I just close the high side port & let the system pump down. It will suck every drop out of the can.

That, or save them for when you do a repair that requires evacuating the system.
Break the vacuum with the refrigerant from the "empty" jug.

Obviously it isn't practical to roll around with a bunch of near empty jugs though.

[anthonyac1]

if the unit has a high side king valve i close it and pump the unit down as i leave the tank open and let the compressor suck it out of the jug. But i dont recommend letting the compressor to run long in a vacuum. once your down to about 10 or 5 psig you got most of it. just something i do.

[ICanHas]

It's all virgin refrigerant, so there's no EPA issues with recovering and selling it, as long as you don't mix it with some used gas.

It was concerning consolidating multiple near empty cylinders into one green disposable cylinders. According to DOT, it's unlawful to transport refilled cylinders. .

[icemeister]

It was concerning consolidating multiple near empty cylinders into one green disposable cylinders. According to DOT, it's unlawful to transport refilled cylinders. .

Yes, that's correct. I missed the part about recovering to a disposable cylinder. An approved recovery tank is OK though.

[icemeister]

I lost my notes for my estimate of 12.5 oz, so I did it again and this time I was a bit less at 11.1 oz. (Don't know what I did different, but that's what I got today.)

(1) define the givens and the assumptions:

• Standard 30 lb R22 cylinder (Assuming 80% full of liquid when new)
• Starting at 75 psig & 80ºF (Typical condition after emptying for an A/C)
• Recover to 15" Hg (Practical lower limit for recovery)

Get some data from ASHRAE Thermodynamic Properties of R22:

(Note that the tables use absolute pressures, so I'll be using 90 psia (75 psig) and 7.5 psia (15" hg) .)

• Saturated Liquid Specific Volume @ 80ºF = 0.0135 cu ft/lb
• Superheated Vapor Specific Volume @ 90 psia & 80ºF = 0.673 cu ft/lb
• Superheated Vapor Specific Volume @ 7.5 psia & 80ºF = 8.86 cu ft/lb

(2) Estimate the actual volume of the cylinder:

• Volume = (0.0135 cu ft/lb x 30 lb) / .80 = 0.50625 cu ft

(3) Calculate the starting and ending weights:

• At 90 psia: Weight = 0.50625 cu ft / 0.673 cu ft/lb = 0.7522 lb >> 12.0 oz
• At 7.5 psia: Weight = 0.50625 cu ft/ 8.86 cu ft/lb = 0 0571 lb >> .91 oz

So the difference is actually just over 11 ounces.

Just for kicks, I did a test to verify my number crunching.

I had an "empty" 30 lb jug of R22 sitting in the shop, which was at a nice 80ºF when I opened up this AM. Its pressure was at 78 psig, so I "adjusted" it to 75 psig, set it on a scale and hooked up for recovery.

When it reached 15" HG the scale just tipped 11 ounces.

[ICanHas]

icy,
have you ever tested weight on brand new vs empty cylinders?

How much contents variation is there and what about tare weight variation?

[icemeister]

icy,
have you ever tested weight on brand new vs empty cylinders?

How much contents variation is there and what about tare weight variation?

No, I don't believe I have. I'm usually more interested on the weight difference when either charging or recovering, so the weight of the tank itself...ie, the Tare Weight, doesn't ever enter the picture.

I have checked new tanks which appeared a little on the light side and found a couple of leakers that way. An R22 30 lb non-refillable Worthington tank weighs a bit over 5 lbs empty (at atmosheric pressure) and the box accounts about 1 lb, so if a new one (in the box) weighs less than 36 lbs, you're short.

[timtech6408]

I would think it would depend on the ambient temp and the tank temp at the time you get down. If your able to get the tank warm enough you can get most of it out. Its a good idea to recover it into a virgin tank so you can use it for another job. But it is below the allowable for the EPA that your able to just open the valve and let it disipate. That last time i really did a large enough system for one bottle I was able to get it down to 8oz. before I had to change bottles. Up to you on what you think is right.

[cy]

A while ago I did a calculation for R22 left in a 30 lb cylinder and came up with 12.5 ounces, which is worth significant dollars these days.

For those of you with Pro member status, here's the thread:

http://hvac-talk.com/vbb/showthread.php?t=1053711

that's a significant amount worth recovering...

[ICanHas]

How volatile is R22 pricing these days? While wholesale price is going up, it was well anticipated when we knew of the ban schedule, so the demand might be reduced for the time being due to stockpiling by end users.

[ICanHas]

do you guys have the tare weight on 25 lbs 410A, 24 lbs 404A, 30 lbs 502?

Does 410A cylinder weigh more owing to higher pressure?

[Six]

410A cylinders are heavier. 8 pounds compared to 6 pounds R22

[ICanHas]

Test result on R12
I had near empty jug of 30 lb size R12 sitting around that I wasn't quite sure what to do with. I weighed the cylinder, took it to an auto repair shop and had them recover it into their machine, which pulls it down to almost 30" of vac.

There was nothing left as liquid, but amount recovered was 10.75oz.

[icemeister]

Test result on R12
I had near empty jug of 30 lb size R12 sitting around that I wasn't quite sure what to do with. I weighed the cylinder, took it to an auto repair shop and had them recover it into their machine, which pulls it down to almost 30" of vac.

There was nothing left as liquid, but amount recovered was 10.75oz.

What was the pressure (and temperature) before recovery?

[atoreson]

Here is something to think about:

In resi work; most times a jug of 22 gets tossed when it no longer has enough pressure in it to push gas into a resi AC (or HP) system. This may well be as high as 60 or 70 PSI gauge... a lot more than atmosphere.

I think I will keep the 'empty' (that is, not enough pressure to draw from) jugs all season. Then as TB noted; in the winter recover it all into a re-usable cylinder.

Yes, I shudder when I see R-22 jugs being tossed at 60 to 70 psi but I am a bit of a cheapskate. I save them and recover them later.

Tony

[atoreson]

How volatile is R22 pricing these days? While wholesale price is going up, it was well anticipated when we knew of the ban schedule, so the demand might be reduced for the time being due to stockpiling by end users.

I think the EPA is a little upset, that the manufacturers found a loophole with the whole DRY CHARGED R-22 equipment.

The EPA regulates the allowable amount of R-22 that can be manufactured in a year and its production is set to cease in 2030. In 2020, however, production will be reduced to a trickle.... 00.50% (if i remember correctly) of 2010 R22 production numbers. I also believe that by 2015, production will be reduced to 10% of 2010 production numbers.

As a result of the DRY CHARGED loophole, the EPA is moving up its R-22 production draw down and that was a big reason for the jump in R-22 price at the beginning of this year. The EPA decided that it would significantly cut the amount of R-22 that could be produced, to combat the loophole.

Tony

[ga-hvac-tech]

I think the EPA is a little upset, that the manufacturers found a loophole with the whole DRY CHARGED R-22 equipment.

MeThinks the loophole was meant to create commerce--- that is keep the chain of manufacturing and installing units going--- in a soft economy.

The EPA regulates the allowable amount of R-22 that can be manufactured in a year and its production is set to cease in 2030. In 2020, however, production will be reduced to a trickle.... 00.50% (if i remember correctly) of 2010 R22 production numbers. I also believe that by 2015, production will be reduced to 10% of 2010 production numbers.

As a result of the DRY CHARGED loophole, the EPA is moving up its R-22 production draw down and that was a big reason for the jump in R-22 price at the beginning of this year. The EPA decided that it would significantly cut the amount of R-22 that could be produced, to combat the loophole.

Tony

I wonder if R-22 will be cheap again (well, maybe not $129.95, which is what I bought it for at Christmas 2011); later in the fall or after the holidays? If it is... I plan to put in a pallet. When R-22 goes away, folks with 22 will have a stash of 'gold' so to say...