The other detail is that I have to give them an elevation for the
bottom of the tank. In addition, there is about 315 equivalent feet
of pipe from the tank to the pump. the building requires a 500 gpm
pump and I plan on calling for an 8" suction line. I was also
thinking about insisting that the center line of the suction line be
6 ft above the centerline of the pump for just that reason.
At 11:56 PM 8/2/2008, you wrote:
Yes - but remember that you have positive pressure when the tank is
filled. (Normally, a horizontal, split-case pump is taking suction
from a tank whose water elevation - when filled - is above the
centerline of the pump). It is only after the tank has nearly
emptied that you'd have a negative pressure condition. At that
point, you'll be in a siphon condition.
Mark Sornsin, PE
Ulteig engineers, Inc.
Fargo, ND
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Russell
Sent: Friday, August 01, 2008 3:57 PM
To: [email protected]
Subject: RE: effective tank volume
Would not anything below the centerline of the pump impellor be a negative
pressure? Split-case centrifugal pumps have to have a positive pressure on
the suction side. Or have I misunderstood the situation?
Russell Rewis
Brown Automatic Sprinklers, Inc.
107C Hemlock Street
Valdosta, Georgia 31601
229-244-8130
[EMAIL PROTECTED]
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ed Kramer
Sent: Friday, August 01, 2008 2:14 PM
To: [email protected]
Subject: RE: effective tank volume
I recently completed a similar project. I agree with Mark, the available
water is that part of the tank below the inlet of the overflow and above the
bottom of the vortex plate. Also, reference NFPA 22 section 4.1.3 (03
edition).
Ed Kramer
Littleton, CO
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:sprinklerforum-
> [EMAIL PROTECTED] On Behalf Of Todd Williams - FPDC
> Sent: Friday, August 01, 2008 7:05 AM
> To: [email protected]
> Subject: effective tank volume
>
> I am working on a project where the water supply for the facility
> will be fed from concrete tank(s). The absolute volume (completely
> full) of the tank is 10098 gallons. A 6" suction line with elbow &
> anti-vortex plate will need to be installed. According to NFPA 22,
> the face of the suction elbow has to be a minimum of 6" above the
> bottom of the tank. The take-out for the elbow is 8" and the top of
> the pipe will be 4" (+/-) above that. I am trying to calculate the
> effective or usable volume in the tank based on what my minimum
> height above the floor can be relied on for suction. Would it be the
> 6" to the bottom of the elbow? 14" to the center line of the suction
> pipe? 18" to the top of the suction pipe? The tank is 10 feet tall,
> so this could have a significant impact on available water. (BTW, I
> am already assuming that the tank will only be filled 9" to 12" from
> the top; would that be reasonable?)
>
> Todd G. Williams, PE
> Fire Protection Design/Consulting
> Stonington, Connecticut
> www.fpdc.com
> 860.535.2080
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
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