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  1. #27
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,351
    Quote Originally Posted by ICanHas View Post
    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.

  2. #28
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,351
    Quote Originally Posted by icemeister View Post
    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 & 80F (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 @ 80F = 0.0135 cu ft/lb
    • Superheated Vapor Specific Volume @ 90 psia & 80F = 0.673 cu ft/lb
    • Superheated Vapor Specific Volume @ 7.5 psia & 80F = 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 80F 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.

  3. #29
    Join Date
    Aug 2010
    Posts
    2,764
    icy,
    have you ever tested weight on brand new vs empty cylinders?

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

  4. #30
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,351
    Quote Originally Posted by ICanHas View Post
    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.

  5. #31
    Join Date
    May 2012
    Location
    Dillsburg, Pa.
    Posts
    4
    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.

  6. #32
    Join Date
    Jul 2005
    Location
    Tulsa
    Posts
    286
    Quote Originally Posted by icemeister View Post
    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...

  7. #33
    Join Date
    Aug 2010
    Posts
    2,764
    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.

  8. #34
    Join Date
    Aug 2010
    Posts
    2,764
    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?

  9. #35
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    410A cylinders are heavier. 8 pounds compared to 6 pounds R22

  10. #36
    Join Date
    Aug 2010
    Posts
    2,764
    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.

  11. #37
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,351
    Quote Originally Posted by ICanHas View Post
    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?

  12. #38
    Join Date
    Jun 2012
    Location
    The Woodlands, Texas
    Posts
    64
    Quote Originally Posted by ga-hvac-tech View Post
    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

  13. #39
    Join Date
    Jun 2012
    Location
    The Woodlands, Texas
    Posts
    64
    Quote Originally Posted by ICanHas View Post
    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

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