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From: RWolf99@aol.com
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Date: Sun, 24 Dec 2000 16:42:29 EST
Subject: Re:  Testing Sight Gauges
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In a message dated 12/23/0 10:22:21 PM, you wrote:

<<If you use compressed air - even from a bicycle pump - BE CAREFUL! >>

This is true.  I once ran a hydrotest on a small rocket engine casing before 
I loaded it with solid rocket propellant.  This gizmo was about 18 inches 
long and about 2 inches ID.  I filled it with water in case it failed.  I 
then had it in a blast chamber at the USAF Academy (where I was a Visiting 
Professor at the time) and pressurized the case from the other side of the 
blast wall.  (I may be crazy, but I'm not stupid.)  The flange on the end of 
the casing failed, and while so doing snapped the bolts holding on the end 
plate.  I was then left with a tube of water with 160 psi air forcing the 
water out one end with nothing to hold it down.

I realized something was amiss when I heard a very large BANG.  I confirmed 
my suspicion when I looked over at the cadet I was working with and his eyes 
were as big as dinner plates.  I then looked at the pressure gauge -- which 
read zero -- and said "oops!"

It took us about five minutes to find the motor case.  It was no longer 
connected to the pressurizing apparatus (which was pretty substantial, by the 
way).  Our first clue as to what happened was the big dent in the ceiling.  
The motor case had launched itself and ripped away from the pressure line, 
then landed on the floor and rolled under a workbench.  Just barely missing 
the $30,000 instrumentation system that the department was storing in the 
blast chamber.

They thought I was being reckless, and I thought they were being stupid for 
using a blast chamber as a storage facility.  Mostly they were just upset 
because they hadn't realized that rocket engine testing was hazardous. (well, 
duh!)  Of course I had been following written procedures, but after this 
incident, a Lieutenant Colonel had to sign them off...

So Dick Alden is right, pressure tests can be hazardous.  I was planning on 
being around the corner and only going to about 50 psi.  And pointing it the 
other way....

- Rob Wolf
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