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CO2 dumping simulation

It occurred to me this AM that you could simulate an end-of-tank condition 
by shutting off the main control valve atop your CO2 cylinder.   So I did 
this with two different regulators I have.   The first one is an old 
rebuilt Norgren from many years ago.   It is the regulator I normally use 
and it will dump.  I measured the following (P1 is input pressure, P2 is 
output pressure):

Time  P1  P2
   0   850   15.1
50   575   15.2
60   500   15.2
57   425   15.2
65   350   15.5
69   300   15.6
73   250   15.2
78   200   15.2
82   150   14.8
87   100   14.0 dropping to zero slowly

P1 stayed at 100  making me think there is a stop in the gauge that 
prevents the needle from dropping below 100 (or else the calibration was 
off, this test was run at about 63F).

Then I tried a new Cornelius regulator from the high-pressure system I sell:

  0   760   15.0
  2   740   15.2
  4   700   15.3
  6   600   16.0
  7  fall    P2 rose quickly to 22, then dropped almost as fast, diffusor 
bubbling like crazy.

You can pretty clearly see the dump, it is interesting to speculate what 
would have happened with a full tank of gas available to dump, instead of 
the few ccs in the stem from the tank shutoff valve to the regulator body.

This again underscores the importance of having a strategy to deal with 
dumping.   I am looking as we speak for a relief valve that can be 
retrofitted into existing systems I have sold since so many folks want 
something more fool-proof.

I am also looking into substituting a regulator that does not dump as 
vigorously as the current Cornelius.   I would like to keep the price point 
pretty much the same tho, so this is a little tricky.

Stay tuned.

Dave Gomberg, San Francisco            mailto:gomberg at wcf_com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam