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Re: Ice Force on Steel Water Storage Tanks

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>The
>dynamic ice pressures mentioned in the AASHTO code (for design of bridge
>piers) are in the range of 100 to 400 psi.  Such pressure would exert huge
>hoop stresses on a tank shell if a significant depth of water froze.
The pressure inside a water tank isn't dynamic, so I don't think there's 
any parallel. My experience with ice formation in tanks and such is that 
you should avoid it. Water expands when it freezes, which is why the ice 
floats in a drink. It'll split steel plumbing easier than you'd pop open 
a pistachio. Free surfaces don't make much difference because ice forms 
at the top; the water below just sits there. Interesting to see a toilet 
tank split clean in two when the water freezes. And even if your tank 
just bulged without fracture, I doubt you could say the same thing about 
the attached piping and valves. 

When I was a kid I read a story about some New Englander who made a fast 
buck buying some old cannon balls that no one else wanted because they 
couldn't figure out how to clean out all the powder left inside. You 
wouldn't dare try to melt them down otherwise. The guy just waited around 
for a cold night, then filled them all with water and spiked in the fuse 
hole. When the water froze it split them all neatly in two, so they were 
easy to clean.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw