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RE: Water hammer

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Any time you have a bend in a pipe, a force is induced by the momentum
change in the fluid. The bigger the pipe and the faster it flows, the
greater the force. The force must either be resisted by external supports or
by the pipe wall. The worst case scenario is a 90 degree bend, in which case
the force in each direction is equal to the flow rate (cfs) times the
velocity (fps) times the mass density (slugs/cubic ft) to arrive at a force
in lbs. For a 12 inch pipe carrying water at 10 fps, this amounts to about
153 lbs, which isn't much. The loads go up as the square of the flow rate,
though, so if you had a really high rate of flow caused by say a broken line
at the bottom, this number could go up dramatically.

Pump surges are pressure rather than flow changes, and would impact the
design of any static thrust restraints and hoop stresses in the pipe. The
mechanical engineer should advise you of any surge pressures if you are
designing the pipe.

One last caution, don't over restrain the pipe in the longitudinal
direction. For a 200 foot riser, you can get a lot of thermal movement which
needs someplace to go.

-----Original Message-----
From: JCohen [mailto:jccpc(--nospam--at)email.msn.com]
Sent: Thursday, August 24, 2000 10:36 AM
To: seaint(--nospam--at)seaint.org
Subject: Water hammer


Are there any dynamic effects to consider in designing the support for a 200
foot vertical 12-inch diameter water pipe, whether regarding to a falling
column of water, air pockets or surge from pumps? The pipe is to be
supported at its base by welding to steel beams at mid-span. No other
vertical support is planned.

Many thanks for any guidance.

James Cohen
jccpc(--nospam--at)msn.com

----- Original Message -----
From: "David Bejan Tehranchi" <dbt(--nospam--at)dbfinc.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, August 24, 2000 10:57
Subject: RE: Patriot - Mel Gibson facts


> You know the Patriot is good.  Mel Gibson's other movies are good, but you
> know what I want to see...
>
> I want to see Mel Gibson play a hardworking. underpaid structural engineer
> who saves the day with a pad of engineer paper, a pencil, and a beat up
old
> copy of the AISC manual.  I want him to complain about "damned architects"
> and "cheap shate contractors" in a movie.
>
> That is the movie I want to see...full of all the real life drama,
> excitement, and courage that makes up my beloved profession.
>
> Until he does that, he's still yet another Hollywod nobody (who happens to
> make good movies).
>
> David
>
> -----Original Message-----
> From: Teresa Dellies [mailto:DelliesTM(--nospam--at)c-b.com]
> Sent: Thursday, August 24, 2000 10:11 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Patriot - Mel Gibson facts
>
>
> As a huge fan of Mel Gibson, I know he IS NOT originally from Australia
> sorry...here's the stats:
>
>
> Birthplace: Peekskill, N.Y.
> Birthdate: 1/3/56
> Education: University of New South Wales
>
>
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