>From a code official stand point the UG inspection is time intensive and will
>usually require multiple trips, prior to any tap being made the UG is
>inspected for trench construction and burial depth, then hydrostatically
>tested, and thrust blocking. Then a fax is sent to the local water company to
>OK a tap, after the tap is completed then a flushing inspection:
HYDROSTATIC: Hydrostatic tests shall be made at not less than 200 psi for two
hours or 50 psi above static pressure In excess of 150 psi for two hours.
FLUSH FLOW RATES
Pipe Size GPM Pipe Size
GPM
4" 400 gpm 5"
600 gpm
6" 750 gpm 8"
1000 gpm
10" 1500 gpm 12"
2000 gpm
After this then I receive a copy of the Contractor's Material and Test
Certificate for Underground Piping form which goes in the file.
PS: Instead of using multiple 2-1/2 hoses, I bring one section of 5" LDH which
is capable of 2000 GPM, the only thing the contractor has to do is supply a
fitting so we can attach a 5" storz connection to the UG.
Satius - Rapidus- Oeconomicus
(Better-Faster-Cheaper)
Frank Herrick
-----Original Message-----
From: Matthew J. Willis [mailto:[email protected]]
Sent: Tuesday, March 30, 2010 3:57 PM
To: Afsa Tech Forum
Subject: Re: Underground flushing velocities
If you have a pump, flows in 20 are higher.
Matt
Sent on the Sprint(r) Now Network from my BlackBerry(r)
-----Original Message-----
From: "[email protected]" <[email protected]>
Date: Tue, 30 Mar 2010 16:47:12
To: [email protected]<[email protected]>
Subject: Underground flushing velocities
NFPA 24 says the following:
NFPA 24: 10.10.2.1.3 The minimum rate of flow shall be not less than one of the
following:
(1) Hydraulically calculated water demand flow rate of the system, including
any hose requirements
(2) Flow necessary to provide a velocity of 10 ft/sec (3.1 m/sec) in accordance
with Table 10.10.2.1.3
(3) Maximum flow rate available to the system under fire conditions
Debate is whether that means that the flow rate dictates the velocity and it
has no absolute requirement or the minimum is 10fps.
Based on wording in the Appendix it would appear that 10fps is the desired
minimum.
So for example I have a flow rate of 8000 gpm (fire flow per local AHJ) and the
line size ends up being 24" Vel= 6.74 fps. Is that acceptable per NFPA 24,
10.10.2.1.3? There are issues with the distance between source and pump
suction and larger pipe equal less friction loss but also lowers velocities.
I read it that it can be less than any one of the following with 10fps being
the minimum. Sometimes simpler wording for non-FP types would make life
easier. <sigh>
Thought, comments, etc?????????
Craig L. Prahl, CET
Fire Protection Specialist
Mechanical Department
CH2MHILL
Lockwood Greene
1500 International Drive
PO Box 491, Spartanburg, SC 29304-0491
Direct - 864.599.4102
Fax - 864.599.8439
[email protected]
http://www.ch2m.com
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