There are some older posts regarding this subject with some really cool pdf files explaining this.

 

can you direct me to one? when i use the search on here, it does not work to good, for what im searching for, alot of times its not found.

 

http://www2.dupont.com/Refrigerants/en_US/assets/downloads/k22202_recovery_cylinder_fill_weights.pdf

 

thanks will check it out

 

80% of the rated bottle.. so a 15 lb bottle you can cram 12 lbs into it ect ect ect

 

so if its a 50lb tank, i take 80% which is 40lb, and then add the tare weight? 28.71lb so 68.71lb total weight? and on the 30lb, 24lb+ tare 17.99lb, so 47.99 total weight, is that right? (what i do now is fill the 30lb close to 30lb, and the 50lb close to 50lb)

 

Your tank should have a WC stamped on it (water capacity, I believe). For Example a 30lb tank will have something like "WC 24.8". Your refrigerant capacity is 80% of the WC weight.

 

thanks again

 

The 80% is volume not weight isn't it?
That's why it would be different weight for different refers.

 

I always used the 80% rule on all refers since the charts are derived from the Specific Weight & Specific Gravity of water.

 

how does a 80% shut off work (i dont have one on my stinger thats why i ask) but wouldn't that go by pressure? and pressure increases with temp, dif with dif refrig, so thats why im confused, i know the 80% is to deal with temp fluctuations causing higher pressure right?

 

volume not pressure

 

You can only fill a recover cylinder to 80% of its capacity by VOLUME. As stated recovery cylinders have their water capacity stamped in it.. They use water as a reference as its density is consistent at room temp 62.4lb/cubic foot..
With this number you can figure out the volume of the cylinder you have.. As an example lets say you have a recovery cylinder with a water capacity of 25 lbs( just a number I picked out if my head)
The internal volume of the cylinder is

D=m/v
D is 62.4 lbs/cubic foot
M= 25
V=?
Solving for volume
V d= m
v= m/d
V= 25/62.4
V= .401 cubic feet

Then using the density of the refrigerant you are recovering at 70deg f let's say its R-22 @72.57 lbs/ cubic ft

D=m/v
M=(d)(v)
M= (72.57)(.401)
M= 29.07 @ 100% full

@ 80%
(29.07)(.8)
= 23.26 lbs

Here's a good article regarding this..

http://www.achrnews.com/articles/on-the-level-filling-cylinders

Hope this helps

 

The WC is the Water Capacity how many pounds of Water the cylinder can hold.
You have to look at the density of the refrigerant, and then;

refrigerant fill factor x Water Capacity x .80 + Tare Weight = Maximum Tank weight.

Once I find this out, I write it on the cylinders with a paint marker....

Cant Read the Tank? Here is a good ref = http://www.worthingtoncylinders.com/Libraries/pdfs/ref_recovery_spec_sheet_sflb.sflb.ashx
Fill Factors - http://hvac-talk.com/vbb/attachment.php?attachmentid=3368&d=1186799730

 

Thanks for the input

 

if you cant do basic math you have no business recovering refrigerant

 

thanks jackbagger!

 

When it starts taking too long to recover, turn the tank in for an empty. That's likely the reason no one ever had a problem with a burst recovery tank as they would have long since been fed up with the recovery times...

 

The difference in volume is also why you see some refrigerants sold as 30 lb tanks and some as 25 lb tanks. They use the same size tanks but there are different specific volumes of the refrigerants so they have to compensate. FYI

 

In the Pro Forum Training and Education dated 3-19-2010 Rundawg posted a chart showing both gross weight and net weight for most refrigerants and for several sizes of recovery cylinders. Search" Recovery Tank Capacity"

 

It is 80% by volume. It's simple to figure out for each refrigerant.. All you need is the density if the refrigerant.. No need to reinvent the wheel here!