Posted by Bill Johnson on February 01, 2001 at 13:23:33:
One of the reasons short-fills occur is because gas pressure is directly proportional to temperature (PV=nRT). As the pressure inside the cylinder increases, so does the temperature of the gas. By the time a cylinder's service pressure is reached, the temperature of the gas inside is much warmer than 70 degrees F (the official temperature for final cylinder service pressure). After the hot fill cools, one has a short-fill.
I just noticed this gem from 49CFR173.301:
(f) Container pressure at 130 degrees F. The pressure in the container at 130 degrees F. shall not exceed 5/4 times the service pressure, except:
(1) Containers charged with acetylene, liquefied nitrous oxide and liquefied carbon dioxide.
(2) When a cylinder is charged in accordance with 173.302(c), the pressure in the cylinde a 130 degrees F. must not exceed 5/4 times the filling pressure authorized therin.
Make good use of this,
Bill