Mike
Memory says FM lifted that speed limit a few years back, and before then it
only applied to pipes 2 in and smaller.
Any FM people in the Forum to comment? Joe?
Jack C Kilavuz
"Mike Brown
(TECH- GVL)"
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15/11/2007 05:48
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I guess being old and having been around for a long time. The 32 ft per
sec came from some old water distribution engineering manuals and became
sort of a rule of thumb for sprinkler calculations in that when you get
above that velocity the friction loss gets larger in a hurry. At one
time FM came out with a requirement for a maximum of 20ft per second in
grid branch lines but they sort of backed off on that issue but did keep
the requirement for the velocity in riser nipples or something like
that. I am not sure what FM does now regarding velocity. Most of the
computer hydraulic programs have followed the old rule of thumb that you
need to keep your velocity at or under 32 ft per second and usually they
will show you the various pipes that exceed that velocity and you can
make the decision on changing the pipe size or not. But the velocity is
not addressed in NFPA 13.
Mike Brown
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Roland
Huggins
Sent: Wednesday, November 14, 2007 3:41 PM
To: [email protected]
Subject: Re: Maximum Velocity
also look at 13: A.22.4.1 (last sentence) It is not necessary to
restrict the water velocity when determining friction loss using the
Hazen-Williams formula.
This is also in the 02 edition.
Roland
On Nov 12, 2007, at 6:41 AM, Brian Harris wrote:
> What's the general rule of thumb for maximum velocities in
> hydraulic calc's?
> I use Hydra-Calc and the default is set @ 32, I assume that's feet per
> second. Where did that number come from, I didn't see anything in
> the code
> book.
>
>
> Regards,
>
> <http://www.firstdefensefire.com/>
>
>
>
>
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