DIYbanter - View Single Post - co2

Trevor Jones

wrote:
Just got myself a co2 tank designed to fill small paintball tanks.

I plan to use this mostly for combat robotics and possibly
for a MIG set up when I get MIG.

I do have SCUBA experience, an air compressor and a TIG set up. But
co2 seems to be a bit of a different horse as it is stored in liquid
form.

Looking for information sources on handling this safely.
Favorite books, web sites, free advice...

Tanks :-) for any help.

DOC

Weigh the tank on an accurate scale while it is empty. Add the rated
capacity to that weight and that will be the maximum that the tank
should ever weigh after a fill.

If you find you have overfilled, no biggie, (other than it being a
waste) just bleed off some CO2 untill you are at the weight desired.

If you do not bleed a bit of CO2 off the tank (recieving) prior to
filling, or you do not place the tank into a freezer or on ice, it
"usually" (!!!) will not take a full charge, as the difference in
pressure is not great enough to flow enough liquid to get a rated fill.
Usually!

Most often, to get a full load on a paintball cylinder, you must
either be doing several at a time (which will load the siphon tube with
liquid) or you must give the tank a squirt, bleed it off (which chills
the tank) then fill it.

A digital scale that you can zero easilly will allow you to weigh the
fill, by zeroing with the empty cylinder on the scale, then weighing the
filled one, to see how much you got.

For personal use, I do not worry about getting right to the rated cap.
If I am paying by the rated cap. of the tank for a fill, I want to get
all the ounces I pay for.

FWIW, a pressure gauge is only really useful as an indicator that you
no longer have liquid CO2 in your tank and are running on gas pressure only.

Somewhere out there on the web is a US Navy chart that shows the
pressure-temperature relationship on a CO2 cylinder, including the
curves for overfills. Normal pressure is pretty steady at around 800 psi
(varies with temperature) but an overfill along with some heat can drive
the pressure WAY up WAY fast!

Overall I'd rate the risk of having a CO2 tank around as less than the
risks posed by the propane tank on the BBQ.

Cheers
Trevor Jones