On 8 Feb 2006 08:57:08 -0800, "chipsoars"
wrote:

As you are probably aware, there is lot of heat generated when filling
the cylinder.

I don't really know how to "generate" heat by transferring a
compressed gas from one storage container to another; yes, the heat of
compression will cause the filled cylinder to get warmer (and the
supplying source to cool), but at the rates to which I am accustomed,
it doesn't get even uncomfortably warm to touch.

Hence the need for hydrostatic testing.

Well, ok? ... Huh?

The cylinder self destructs if it fails the test.

I've personally done only 4 hydrostatic tests of cylinders; one failed
because the recovery was too little. We filled with deionized water,
pressurized to 5/3 stamped pressure measuring water needed to do so,
then verified that we got (man, I've forgotten that number, think it
is 95%) out dropping back to atmospheric .

I've witnessed perhaps 200; none that failed was exciting. What other
method of hydrostatic testing is used?

Now the one talked about in every scuba shop in the country ...
1960's, I'd guess? ... when a guy's buddy told him he'd give him a
GREAT paint job on his cylinder at his "paint" line at work ... and
the freshly powder coated cylinder was being filled with air ... the
heat treated aluminum tank was annealed during powder coating and my
memory is that the explosion killed and injured and did lots of
property damage.