Does 'totally aware of NPSH' mean you can tell me what causes cavitation? On Feb 11, 2016 4:56 PM, "Travis Mack, SET" <[email protected]> wrote:
> 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 >>>>>> >>>>>> _______________________________________________ >>>>>> Sprinklerforum mailing list >>>>>> [email protected] >>>>>> >>>>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprink >>>>>> l >>>>>> er.org >>>>>> >>>>>> _______________________________________________ >>>>>> >>>>> Sprinklerforum mailing list >>>>> [email protected] >>>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl >>>>> er.org _______________________________________________ >>>>> Sprinklerforum mailing list >>>>> [email protected] >>>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl >>>>> er.org >>>>> >>>>> _______________________________________________ >>>> Sprinklerforum mailing list >>>> [email protected] >>>> >>>> >>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>>> _______________________________________________ >>>> Sprinklerforum mailing list >>>> [email protected] >>>> >>>> >>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>>> >>>> _______________________________________________ >>> Sprinklerforum mailing list >>> [email protected] >>> >>> >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>> >>> _______________________________________________ >> Sprinklerforum mailing list >> [email protected] >> >> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >> > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
