Totally aware of NPSH, and calculating velocity in the suction piping
and also how to read a table that indicates minimum sizes.
The pump has been in service for years. I assume that it has never
drawn into negative suction pressures. However, that still doesn't
relieve the requirements to meet the tables in NFPA 20. The system
design was done by a technician and not a PE, so there is not the option
to supercede the tables that provide minimum suction pipe sizing. And
since the velocity of 1500 gpm in 6" sch 10 piping is 15.2 fps, that
exceeds the 15 fps limit set in 20. So, regardless of NPSH or not, it
exceeds the 15 fps and the tables in 20.
Regardless, the pump has been problematic for the building owner and it
will be replaced. I was just curious based on the things I saw on it.
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Drive
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
http://www.mfpdesign.com
https://www.facebook.com/pages/MFP-Design-LLC/92218417692
Send large files to us via: https://www.hightail.com/u/MFPDesign
On 2/11/2016 3:48 PM, Brad Casterline wrote:
As a Standard, 20 has to draw some lines somewhere Travis.
Brush up on NPSH.
Then, since you have as builts, maybe the pump data is around too.
The main thing is that available NPSH is equal to or greater than required
NPSH!
On Feb 11, 2016 4:40 PM, "Travis Mack, SET" <[email protected]> wrote:
Even if the increaser is technically OK, the 6" suction pipe could be a
problem. I haven't calc'd it yet, but that may put the velocity in excess
of 15 fps for the suction piping.
I'm pretty certain they are going to replace the pump and just upsize the
suction piping for the 10 pipe diameters to be in compliance with NFPA 20
current edition.
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Drive
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
http://www.mfpdesign.com
https://www.facebook.com/pages/MFP-Design-LLC/92218417692
Send large files to us via: https://www.hightail.com/u/MFPDesign
On 2/11/2016 3:35 PM, [email protected] wrote:
Then technically that makes the "6x8 Increaser" okay doesn't it?
Mark at Aero
602 820-7894
-----Original Message-----
From: Sprinklerforum [mailto:
[email protected]] On Behalf Of Travis
Mack, SET
Sent: Thursday, February 11, 2016 3:16 PM
To: [email protected]
Subject: Re: NFPA 20 around 1988
I have yet to get any pump test information, but I assume it has been
tested properly.
Thanks for the confirmation of the reducers. I was pretty certain that
you couldn't use a concentric back in the day, but I didn't have the
standard to verify it.
What's funny is the pump is 8x6. They ran a 6" underground and piping up
to the suction of the pump, then had to put an 8x6 flanged "increaser" to
match up with the pump. You would think that some one would have had the
idea back then that this didn't seem quite right.
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Drive
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
http://www.mfpdesign.com
https://www.facebook.com/pages/MFP-Design-LLC/92218417692
Send large files to us via: https://www.hightail.com/u/MFPDesign
On 2/11/2016 3:12 PM, Scott Futrell wrote:
I thought Brad would have the suction size answer!
Suction size has been for some time based upon the pressure remaining
above 0 psi when flowing at 150 percent of the rated capacity. So, 6"
might be possible, but you'd have to verify the supply.
Agree completely, no concentric on suction side.
Scott
Office: (763) 425-1001 x 2
Cell: (612) 759-5556
-----Original Message-----
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Brad Casterline
Sent: Thursday, February 11, 2016 4:08 PM
To: [email protected]
Subject: Re: NFPA 20 around 1988
No to concentric on suction side---
Requires ECCENTRIC, top flat.
(if this is vertical in-line, different ballgame) On Feb 11, 2016 3:58
PM, "Travis Mack, SET" <[email protected]> wrote:
Was it ever permitted for a 1000 GPM pump to be supplied by 6" piping?
Also, was it ever permitted to put a CONCENTRIC 8x6 reducer on the
suction flange of a pump.
We have an existing project where the owner was hoping to remove the
pump and to supply from city water. I informed them that the water
pressures on site were not compatible. They also have a pump that
has been requiring a lot of maintenance. As I looked at the as-built
plans (yeah, miraculously they had them for a building built in
1988), it shows a 6" supply for the
1000 gpm pump and the concentric reducer on the suction flange of the
pump.
In the most recent editions of NFPA 20, a 1000 gpm pump needs an 8"
suction line.
--
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Drive
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
http://www.mfpdesign.com
https://www.facebook.com/pages/MFP-Design-LLC/92218417692
Send large files to us via: https://www.hightail.com/u/MFPDesign
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