pyotr filipivich wrote:
snipped
I have heard that a properly anchored chain link fence has good "crash
barrier" properties. Considering what happened when the acetylene tank
crashed into one, it might work for a car. [Tank fell over, knocked off
the valve, rocketed across the shop, through the wall, twenty five feet to
the chain link fence, was snagged by the chain link fence and pulled about
a hundred and fifty feet of it loose from the fence posts.]
I have been under the impression for a long time that valves used on
portable high pressure tanks have a definite designed in "weak point"
with an orifice below it small enough to limit gas flow to rates which
won't cause "rocketing." When impacted hard enough, the valve is
supposed to snap off beyond that orifice.
At least that's what I heard 40+ years ago about the "J" and "K" valves
we used on our Scuba tanks. Can someone straighten me out on this point?
'Course there's alsways some fool who will beat the most foolproof
systems man can think up. Lots of us used fire extinguisher bottles as
diving tanks in the early days of Scuba, they were rated for 1800 psi
and were a heck of a lot cheaper than "official" tanks. Worked just fine
if you used them correctly.
I still get shivers when I remember what happened to a guy in our diving
club. We had to use 3/4" to 1/2" NPT reducing bushings to adapt the 1/2"
threaded Scuba valves to the fire extinguisher bottles. Only this poor
guy didn't know the difference between materials and used a cast iron
plumbing bushing instead of a steel one. The threads sheared off the
bushing the first time he filled the tank. The valve blew out and
entered his head under his chin, killing him on the spot.
Sad story, but it sure increased my respect for the amount of energy in
compressed gasses. I think of that guy everytime I see a compressed gas
bottle standing up without a safety chain to keep it from falling.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"As long as there are final exams, there will be prayer in public
schools"
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