Safety distance for pneumatic test 1

[PAN]

Refer to the related thread,

Equivalent Energy
thread794-26767

I don't want to reply the dead thread. Therefore, I ask this question in new thread.

I got the proposal for pneumatic test with safety protection (barricade the area) around minimum distance of :-
+100 ft. for stored energy 27,134 kJ.
+150 ft. for stored energy over 27,134 kJ.

I cannot find the source of reference for above proposal. It's seem the safe practice from the contractor's experience.

Should we accept this idea? Please share your experience.

 

[codeeng]

I have a spec here that states:

E = {P.V/k-1} [1-{Patm/P}^k-1/k]
where
E = Energy Joules
P = Absolute pressure Pascals
V = Test Volume m^3
Patm = Atmospheric pressure pascals
k = Ratio of specific heat of air

TNTlb = E 4.8 x 10^-7
where
TNTlb = Equivalent TNT in pounds

SD = 15 (TNTlb)^0.5
where
SD = Safe distance meters

This compares reasonable well with your numbers. Not sure of the original source.

 

[JStephen]

Suppose you take the volume of gas as a sphere. Then let it expand (reversibly)- you can then calculate pressure at each radius. Assuming a piece of plate was out in front of that pressure, you could calculate velocity of the plate and then a reasonable safe distance. This procedure should be conservative, since actual expansion is not reversible, and pressure is reduced since ball of gas is not 100% contained at each point.