Attn. Nov71
‘O2 escaping at high pressure even from a slow leak, can create high temps (adiabatic ) The presence of a small amount of oil/grease can cause ignition’
Sorry, but you're wrong on this point. Adiabatic expansion (and compression) is a system that applies to confined gases that remain confined throughout the process. Escaping gas is not an adiabatic system. Adiabatic compression makes the gas hot, with no loss of heat to the surroundings; adiabatic expansion sees the gas cooling, but again with no heat transfer.
What we have here is the question of escaping gas, which has nothing to do with an adiabatic system. When you release a CO2 fire extinguisher — the cannister and contents being at ambient temp — the gas that emerges is very cold. This is what happens when any compressed gas is allowed to expand rapidly. The gas absorbs a great deal of heat from the surroundings. The warnings on BOC cylinders are about the danger of combustion in the presence of O2.
Last edited by Vertiginous; 28th Jul 2008 at 13:20.