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Danger associated with heat and bursting N2O bottles.

The temperature/pressure behavior of N20 when it is above the critical temperature (Tc - 97.5°F / 36.4°C) is of major importance in any discussion about heating or over- pressurizing nitrous bottles and system components.

In the context of preventing over-pressurization of bottles and nitrous systems, it is of primary importance.

Below Tc, in the “normal” range of operating pressures, the pressure is dependent only on the temperature. Bottle pressure at a given temperature is the same if the bottle is 50% or 100% full.

Above the critical temperature (Tc), N2O pressure becomes dependant on not only the temperature but also the mass contained and the volume of the container.

Above Tc (more than 97.5°F), more or less mass N2O in the same volume bottle will have more or less pressure at the same temperature. (This TxM/V = P behavior of fluids in the super-critical state is common to all fluids, not just nitrous.)

A small increase in N2O mass, such as from over-filling, will dramatically elevate bottle pressure at temperatures above Tc (97.5°F).

The following information is extrapolated from a calculator for this purpose in the NIST (http://www.nist.gov/index.html ), which is a .gov domain. Presumably, the information is reasonably accurate in a .gov website. The pressures calculated there are equivalent to the pressures calculated with the physics math in the permanent memory of a HP48GX scientific calculator.

Confusingly, the HP calculator and the several sources of information in several physics books I have and those available on the web are not in exact agreement of the calculated pressures. However, they all are similar and show the same trend of rapidly increasing pressures with increasing temperatures above Tc. The most important common fact they all agree on is the extreme pressure sensitivity to small amounts of additional mass in the bottle at a given temperature above the critical point.

At the following above critical temperatures, with the following amounts of N2O in a standard 10 lb. bottle (5.9L volume) the pressures can be:

9 lbs. N2O @ 110°F = 1570 PSI
10 lbs. N2O @ 110°F = 2150 PSI
11 lbs. N2O @ 110°F = 3350 PSI

9 lbs. N20 @ 120°F = 1850 PSI
10 lbs. N2O @ 120°F = 2550 PSI
11 lbs. N2O @ 120°F = 3850 PSI

9 lbs. N2O @ 130°F = 2100 PSI
10 lbs. N2O @ 130°F = 2940 PSI
11 lbs. N2O @ 130°F = 4350 PSI

 

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580 Stang, @ 9# of refill, what will a 10# n20 bottle weigh? Minie weighs right at 24.12# after they are "full". Thx.
 

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EXCELLENT INFO!!!!!!!!!!!!!!!!! Thanks 100times, this could really save some lives around here!!!!
 

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580 Stang, @ 9# of refill, what will a 10# n20 bottle weigh? Minie weighs right at 24.12# after they are "full". Thx.
FoFo is that a "trick" question.........lol

All most all bottles will weight different because of the different valves and / or jewerly (gauges, blow of fittings, etc) Some won't even weigh correctly empty when new. That 24.12# is just an industry standard sticker IMO.

Weigh your bottle empty and write that weight on the bottom and try to use the same scale at all times. This will tell you exactly what your bottle should weigh with 9#, 10#'s, etc of Nitrous in the bottle.
 

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580 Stang, @ 9# of refill, what will a 10# n20 bottle weigh? Minie weighs right at 24.12# after they are "full". Thx.

I would say if the are 24# 12 oz Full (10 pounds) then they would be 23# 12 oz with 9 #'s in them... Am I close ?? ;) Also cool info in this post as well... SJ
 
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