i concur. Pipes freeze in houses because the segments that freeze eventually meet up and burst as eventually the expanded ice (in a full system or retained water region) ultimately has nowhere to go longitudinally (as George said by displacing) grows radially and bursts the containment. Local freezing is different as long as the ends are free to expand. HOuse pipes are thin wall copper or PVC (or pex) and the burst pressure is not comparable with industrial black pipe.
Put a pop can in the freezer, good demonstration of hoop strength twice the longitudinal (slight thickness variability overlooked), but the ends bulge, it does not burst.
We've done lots, especially for "hot" taps into live systems... you dont need cryogenic temps to get a functioning freeze plug (it just forms faster with colder source). Its even possible to introduce into gas lines, we've done freeze plugs into hydrogen lines for "hot" tap, and the hydrogen bypass leakage was minimal enough for safety. THe holding force is enormous/substantial. Ive never seen one break free, but stopples do.
The comments have been sound advice and obvious. Dont perform hot work anywhere near the freeze plug, leave the ends unrestrained, dont do it anywhere near rigid components valves or anything that freezing would damage (anything with close fitting internals), block in the pressure to hold system pressure, slow the flow down enough. Use the volume change to check the burst pressure limit on the pipe wall. It never reaches this because the volume displaces longitudinally.
Al
-----Original Message-----
From: George McKinney [mailto:gmckinney@augustaeng.com]
Sent: Thursday, July 29, 2004 12:17 PM
To: PipingDesign@yahoogroups.com
Subject: Re: [PipingDesign] Use of ice to plug a pipe
Chris:
Actually, as long as you don't block the ends, you shouldn't have problems.
The method under discussion is to make a localized freeze, as opposed to
your situation, where the whole piping system froze. In that case, the
still liquid water has no place to go, and builds up the pressure. But if
it is a localized freeze, the liquid water just gets displaced, and the ice
plug doesn't build any significant pressure. Moral - you can use a freeze
stopple, but DON'T close the block valves (or have a relief valve that will
bleed off the pressure).
George McKinney
>Has anybody used a similar method for temporarily plugging a pipe?
Lots of people have in Minnesota. Regrettably the side effects involve
broken pipes or fittings, because water expands when it freezes. The pipe
usually unplugs itself at some point when it splits. I once inspected a
small house which was temporarily unoccupied when the furnace failed. The
water and hot water heating pipes had frozen the pipes and fittings had
split at many points in the system. Even the toilet tank had cracked, as
did cast radiators and pipe runs, without any pattern that was
immediately obvious.
I heard a story in grade school that some early American inventor once had a supply of surplus cannon balls that he wanted to sell, but couldn't because there was no way to guarantee that all the powder inside was gone. The guy simply filled them with water one winter night and spiked the fuse hole. Mother nature did the rest--the next morning every one had split neatly.
The upshot is that freezing the pipe generates tremendous internal pressure. If the plug is truly solid, you'll probably rupture the pipe.
Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen. ___________________________| John Sedgwick, Spotsylvania 1864)http://www.skypoint.com/~chrisw
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Received on Thu Jul 29 15:06:00 2004
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