CO2 canister-refills & retests -- strectch marks & strecthing dollars

["S. Hieber" <shieber at yahoo_com>]

I paid about $80 for a seamless steel tank, tested and certified for
over 2000 psi.

They are required to be tested and restamped every five years (DOT
regs).  The repeated pressurizing/depressuring causes
expansion/contraction of the tank (yes, it's bigger when it's filled)
that eventually stretches the metal.  The stretch marks are weak points
in the tank.  If a tank stretches too much, its skin is too weak and
needs to be replaced.

I asked my local CO2 supplier if they tested and for how much.  The
answer was, "Yes, we can do the test and restamp the tank and have you
all set for another five years.  Leave it overnight if you can.  Cost
you 8 bucks."   They can do it while you wait.  I didn't ask how long
the wait was.

Eight dollars is a buck sixty avg. per year -- test cost doesn't seem
like a reason for swapping tanks.  At least not if you have someone
local that can do it.  But, if the swapping arrangment means you don't
have to buy a tank, just put down a security deposit, then swapping
isn't a bad way to go at all.  Even more so if your local supplier has
to send tanks away to be tested.

Just for reference, my "10 pound" tanks have a tare weight of about 12
pounds each and can receive up to 5 pounds of CO2 each (that's about
850 psi at room temp).  A fill costs $11 dollars -- down from $15 a
year ago.

Scott H.

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