On Wednesday, May 10, 2017 at 2:02:25 PM UTC-4, Carl Ijames wrote:
"rangerssuck" wrote in message
...

The refrigerant pipes in a typical rink are about 10 or 11 miles long
(seriously), and are (sometimes) 5/8 OD thinwall steel, but that's a
variable.
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Just as a sanity check when you do the pressurize with nitrogen test, I get
a volume of 72 cu ft or 2039 L for 10 miles of 1/2" ID tubing. At STP, 0 C
and 101 kPa nitrogen has a density of 1.25 g/L so at STP 72 cu ft would
weigh 5.62 lbs (I'm ignoring the difference between room temperature and STP
for this estimate :-)). If you start at atmospheric pressure you would need
3x72 cu ft = 216 cu ft to reach 44.1 psig which should be completely safe
since the vapor pressure of R22 at 75 F is 132 psig. So you will need at
least a couple of tanks of nitrogen on hand to be safe, and a refrigeration
scale that can do 0.1 lbs at the weight of a full tank of nitrogen with
regulator should let you get an answer in the 5-10% range. Have fun.

--
Regards,
Carl Ijames

I've got 300cf of nitrogen in one big tank, an accurate temperature sensor buried in the concrete and a scale that's good to 1% or so at the weight of this tank.

And thanks, I do expect this to be at least a little fun.