[PSUBS-MAILIST] Propane Tank" fatalities?

[protek@shreve.net]

     I'm curious.  I have an older version of PVHO (over 10 years old) that 
outlines what's necessary for complying with the standard.  Not only does 
it specify materials and techniques, it specifies that all pressure bearing 
welds have to be X-rayed.  It says that once complete the vessel must be 
pressure tested in a chamber, after which any paint around welds must be 
stripped and the metal joints dye-checked.  On top of this, all windows 
must conform by being properly annealed in an oven at least twice.  And 
when I say "Properly Annealed" I mean heated at a specific rate and cooled 
at a specific rate.  I actually did this for my windows and it took a total 
of about 20 hours each in an oven controlled by my desktop computer.
     I'm not saying that this should not be done, but I am truly curious to 
know if those who have built subs have complied with 100% of this 
standard.  If anyone builds a sub and complies with 98% of the standard, 
they are out of compliance.  There are numerous components to this standard 
and I suspect that some feel that they are in compliance when they are 
truly not.  Have you X-rayed each pressure bearing weld?
     I'm not sure of the metallurgy of the standard propane tank or how 
they weld.  But, I know of successful subs make out of 0.25 inch thick 
material properly braced.  My sub is about 0.4 inches thick but I don't 
have as much internal bracing as I would have used with thinner 
material.  I would imagine that propane tanks are in many cases thicker 
than the 0.25 inch value.

Gary Boucher