There was an equalization in pressure as @forgedhybrid stated. If your tank was under vac when you started there shouldn’t be any air in your system. You want your receiving vessel colder or your source tank warmer to create the pressure differential.
if he filled it with a tank that had air there could be. I didnt consider that he may have not chilled the receiving tank
He had a full 100lb tank. Very doubtful it came with atmosphere in the tank.
I know you’ve said you gravity feed with 20lb tanks and also recover into the same tank, correct? Injecting through a dip tube requires a pressure differential.
everything is pressure differential, I assumed everyone knew that. I remember when I first started, I thought liquid at the top automatically went down like water.
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Yes, only difference is with gravity feeding your gas will continue to flow as it condenses in the receiving vessel. With a dip tube you’re done once the pressure equalizes unless you create a differential.
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Thank you guys! That is really helpful! I vacced down both tanks to -30 before adding the 70/30 mix. One tank is the 50# yellowtop and then i have a ~30# tank from bhogart. Ill probably chill the solvent tanks i dont feel comfortable heating up that new 100 gal tank without the proper equipment lol. Ok so it makes sense with the pressure differences. What about using the recovery pump i have to just suck it into my tank? Or would that not be efficient since itll heat up the gas right?
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Recovery pump will require a coil to chill the gas. Are you distilling the new gas before filling the tanks?
you need to chill the tank, it wont just flow. If you use a pump you need chilling coils because the pump heats it up like crazy. it can be as easy as bags of ice and some salt and itll get plenty cold. you need the gas to condense in the recovery
I have a passive system setup so i could use the coil i have. I didnt distill the gas into the yellowtop since i figured it was just as dirty if not more lol. I can do a run to distill the gas before i do the stainless tank from bhogart though. Just did a pressure test last night on this system so im ready to do a run finally once i get the gas ready!
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itll be a learning experience, but with lots of dry ice its easier.
Yea thats what im expecting 
have all teh tools youll need in one place, you may need to adjust valve packing so have the right sized allen and an adjustable wrench handy.
So, i’m a n00b to CLS and i would like to recover Whip it Premium Butane into my 30# tank. I did the math and wanted to make sure i was correct before i go doing anything…
The MSDS sheet says Whip It has a relative density (i’m assuming this is the specific gravity?) of .559. also according to it’s MSDS It’s make up is 54% N tane, 24% iso, and 22% propane.
SO: 30# / .0361 = 831
831 x .8 = 665in3
specific gravity of whip it .559 x .0361 = 0.0201799
665in3 x .0201799 = 13.4196335lbs of whip it in a 30# tank, Correct?
hopefully this post doesn’t annoy you. Just trying to be safe over here.
edit: the reason i would like to use whip it is due to its ability to move at a lower temperature than the pure Ntane i can source locally and i can’t seem to find a mix very close to me.
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Yup, I get the same thing.
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Look at u helping out😊
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Just for jollies, I compared Whip it’s MSDS .559 stated density to my calculated density and discovered a disparity if it is indeed 54% n-Butane, 24% Isobutane, and 22% Propane. Not enough to significantly affect your calculations, but with the new specific gravity figures, here are the calcs:
(.54 X .601) + (.24 X .563) + (.22 X .495) = 0.32454 + 0.13512 + 0.1089 = 0.56856 specific gravity
0.56856 X 0.0361 = 0.02053 lbs/in3
665 in3 X 0.02053 = 13.65 lbs
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Because we extract with refrigerants.
Here’s a follow up for the big brains.
How much vapor do you need to let loose to “auto refrigerate” down to the boiling point of your solvent. Propane to -44f. Butane to 0f. Let’s assume 100lb tank insulated tank. And a starting temp of 70f.
Follow up question. Once we hit 0psi, if we begin pulling on the vapors with a trs21 what is lowest temp practically achievable for each solvent.
Also what changes if instead of venting then pumping to atmosphere, we vent then pump into a holding tank for later recovery.
Edit @Graywolf ?
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A 100# tank is its rating for water, and it can only be 80% filled for LPG.
Butane has a specific gravity of .601 and Propane is .495 so it would hold 100# X .80 X .601 = 48 lbs of Butane and 100# X .80 X .495 = 39.6 lbs of Propane.
70F – 30F = 40F DT Butane
70F + 44F = -114 DT Propane
48# X 0.39 SpHt X 40F DT = 749 BTU
39.6# X 0.39 SpHt X 114 DT = 1761 BTU
749 BTU / 165.6 BTU = 4.5 lbs Butane vaporized
1761 BTU / 184 BTU = 9.6 lbs Propane vaporized
-22” Hg is about the lowest practical pressure to run a TRS-21 without running the piston rings dry and according to the calculator at Boiling Point Calculator , at -22” Butane boils at -5C/23F and Propane at about -45C/-49F.
Ummm could you elaborate on the last question?
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Hypothetically of course, my last question presumed there would be greater heat removal at sub atmosphere. I understand some folks vent tanks to lower their solvent temperature and I was curious how low they would go with a refrigerant pump. Not as low as I assumed. Thanks for mathing that one out. I’m glad I don’t run pumps.
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Jesus, you guys truly are on another level 
I hope to absorb as much info from you guys as possible! Thanks for your in depth answers, explanations and maths!!
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