[TheForge] Re: incompressible water expands suddenly, film at eleven

[info@reciprodyne.com]

> From: Andy Vida <osan@netlabs.net>
> As far as I know there is no terrestrially
> attainable pressure that will compress a body of pure water.


Dear Andy,

You are probably right in a theoretical sense, I won't attempt to argue.
However, in the real world, pure water (or "pure oil") are scarce
commodities.

It is never wise to assume a pressurized fluid system is not somehow storing
energy, whether it is the fluid or the structure. In my experience, it is
usually a combination of both.

As a teenager, I was doing a hydro test on traction engine boiler. Routine
stuff, done it before, hum de dum.

Well, I filled up the boiler, tapped and flushed and made sure it was filled
to the top, solid. Hooked up the pump, bled the lines, etc. pumped up the
pressure, checked for leaks etc. All good.

It then occurred to me that completely forgotten to install a valve of some
kind to let the pressure out. I had plugged every hole solid with a plug.
The boiler was tight as a drum, so there was nothing to do but remove a plug
somewhere and hope for the best.

I chose the plug where the blow down valve would have been, near the bottom
of the firebox. Carefully started unscrewing the plug, no dribbles, no
squirts. Stood to one side, expecting to get drenched, but no water appeared
at the threads of the plug. As I got to the point where I thought the plug
should have dropped out, it was still dry. The plug was turning easily
(thanks, NevrSeez), and for some reason, my brain decided that this
particular plug must not have any pressure on it, so I carelessly gave a
final twist. POW!

The plug shot more than 50 yards, I measured. The water that sprayed out the
hole carved a gouge about 20 feet long, and a foot deep in the gravel. Good
thing there wasn't a family with a baby carriage happening along just then.

My best guess is that that particular water had a lot of air entrained in it
from the hydrant, and all those billions of tiny bubbles equaled one big
bubble, and that bubble pushed a lot of solid water out ahead of it as it
expanded, and by golly, it expanded quite a lot. Made an embarrassing roar
for three or four seconds.

The point is, theoretical conditions never occur in nature, or in industry
for that matter, so, frankly, many theoretical discussions become moot in
real life. Therefore, ipso-fatso, to expect theoretical results from a
potentially dangerous real-life system is maybe not very smart. Or as Thomas
Edison used to say, "THEE-oh-RET-ickal!".

Tom Troszak