Fine I'll play with myself. Example: 90 psi. 1775 rpm. 90/.433=207.9 ft. v=sqrt (2gh)=115.7 ft/sec. So at the circumference of the impeller the water is going 115.7 ft/sec. For velocity in a circle: v = 2 * PI * r * f, where r is the impeller radius in feet, and f is the revolutions per second-- 1775/60 = 29.583. By rearanging we get: r = v / 2 * PI * f, r = 115.7 / 2*PI*29.583 = .62246 ft., times 2 times 12 = 14.94 in diameter.
I have never been more than one inch off, and that was with a 2500 gpm pump. bc On May 18, 2016 6:05 PM, "Brad Casterline" <[email protected]> wrote: > No such things as poorly worded or difficult positions here. > The range of this Forum allows anyone to let their hair down and just > blurt stuff out.,.,. even me :) > > ps, you ar'nt by any chance looking at a pump nameplate right about now > are you? > > Brad Casterline > On May 18, 2016 5:55 PM, "Zachary Siegrist" <[email protected]> > wrote: > >> It appears my question was poorly worded so it put y'all in a difficult >> position to answer. Travis and David supplied the answer I needed. >> Thank you all for your help. This has been informative. >> >> On Wednesday, May 18, 2016, Brad Casterline <[email protected]> >> wrote: >> >>> This is Brad not Zach David. >>> While we are waiting I just wanted to say I have been asking for 4 or 5 >>> years here if someone will dig up an old certified pump curve and post the >>> nameplate psi and rpm. I am 99.44% (like Ivory soap) sure >>> I can tell you what the nameplate impeller diameter says. >>> Are you game? >>> >>> Brad >>> On May 18, 2016 5:26 PM, "David Bitton" <[email protected]> >>> wrote: >>> >>>> Hello Zach, >>>> >>>> >>>> >>>> In reviewing the various responses to this thread, I noticed that no >>>> one actually answered your original question. Here's my attempt: >>>> >>>> >>>> >>>> The upper limit for the pump pressure rating can be estimated as >>>> follows: >>>> >>>> >>>> >>>> Nominal pressure = (175 psi - Y)/1.2 >>>> >>>> Y = Maximum suction pressure (static pressure if the pump is fed by >>>> municipal mains) >>>> >>>> >>>> >>>> This formula is based on the following assumptions: >>>> >>>> 1. The maximum pressure rating for the piping and system >>>> accessories is 175 psi. >>>> >>>> 2. The pump shut-off pressure is 120% of the pressure at the >>>> rated flow (this can range from 100% to 140%, depending on the pump model). >>>> >>>> >>>> >>>> In addition, if the proposed pump will be driven by a diesel engine, >>>> the nominal pressure derived from the above expression may be divided by >>>> 1.21. The result would be the maximum pump pressure rating that would not >>>> require the installation of a relief valve. >>>> >>>> >>>> >>>> *David Bitton, ing.* >>>> >>>> *Les services de prévention des sinistres Quest inc.* >>>> >>>> *Quest Loss Control Services Inc.* >>>> >>>> 5100, rue de la Savane, bureau 200 >>>> >>>> Montréal, QC H4P 1T8 >>>> >>>> (514) 341-4545 >>>> >>>> *www.questlosscontrol.com <http://www.questlosscontrol.com>* >>>> >>>> >>>> >>>> >>>> >>>> *From:* Sprinklerforum [mailto: >>>> [email protected]] *On Behalf Of * >>>> [email protected] >>>> *Sent:* Wednesday, May 18, 2016 5:15 PM >>>> *To:* [email protected] >>>> *Subject:* RE: Equation for sizing fire pump >>>> >>>> >>>> >>>> In some jurisdictions you have to install an automatic suction control >>>> valve to assure that you do not pull the municipal system lower than their >>>> prescribed pressure. >>>> >>>> >>>> >>>> Typically the 20 psi flow point is provided on hydrant flow tests most >>>> of the time by extrapolation. If you have that data then determining if >>>> the pump will draw more than allowed is much simpler. >>>> >>>> >>>> >>>> >>>> *Craig L. Prahl* >>>> Fire Protection Group Lead/SME >>>> *CH2M* >>>> 200 Verdae Blvd. >>>> Greenville, SC 29607 >>>> Direct - 864.920.7540 >>>> >>>> Fax - 864.920.7129 >>>> >>>> CH2MHILL Extension 77540 >>>> [email protected] >>>> >>>> >>>> >>>> *From:* Sprinklerforum [mailto: >>>> [email protected]] *On Behalf Of *Zachary >>>> Siegrist >>>> *Sent:* Wednesday, May 18, 2016 5:07 PM >>>> *To:* [email protected] >>>> *Subject:* Re: Equation for sizing fire pump >>>> >>>> >>>> >>>> Yes, I was confusing sizing the pump with determining the max capacity >>>> for the pump. Trying to avoid dropping below 20 psi which has been a >>>> problem in my jurisdiction. Thank you Brad for your substantive reply. >>>> On Wednesday, May 18, 2016, Brad Casterline <[email protected]> >>>> wrote: >>>> >>>> Please brush up on NFPA 20. >>>> >>>> bc >>>> >>>> On May 18, 2016 2:48 PM, "Travis Mack, SET" <[email protected]> >>>> wrote: >>>> >>>> I think he is trying to get at the max capacity of a pump so that the >>>> municipal water supply doesn't go below 20 psi. So, if his factor comes to >>>> a max of 1200 and the system requires a 1500 gpm pump, then a tank is going >>>> to be required. That is my assumption at least. >>>> >>>> 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 >>>> >>>> LinkedIn: https://www.linkedin.com/in/travismack >>>> >>>> On 5/18/2016 12:46 PM, [email protected] wrote: >>>> >>>> Still not sure what that is supposed to represent or what you’re >>>> trying to calculate. >>>> >>>> >>>> >>>> >>>> *Craig L. Prahl* >>>> Fire Protection Group Lead/SME >>>> *CH2M* >>>> 200 Verdae Blvd. >>>> Greenville, SC 29607 >>>> Direct - 864.920.7540 >>>> >>>> Fax - 864.920.7129 >>>> >>>> CH2MHILL Extension 77540 >>>> [email protected] >>>> >>>> >>>> >>>> *From:* Sprinklerforum [ >>>> mailto:[email protected]] *On Behalf Of >>>> *Zachary >>>> Siegrist >>>> *Sent:* Wednesday, May 18, 2016 3:42 PM >>>> *To:* [email protected] >>>> *Subject:* Re: Equation for sizing fire pump >>>> >>>> >>>> >>>> Sorry, I am looking at the wrong equation. That equation just ensures >>>> I have 20 psi available at 159 percent. >>>> >>>> On Wednesday, May 18, 2016, <[email protected]> wrote: >>>> >>>> What are you supplying with your pump? >>>> >>>> >>>> >>>> I’m not seeing any correlation between a flow at 20 psi and sizing a >>>> pump. What flow are you talking about, a municipal flow rate or what? >>>> >>>> >>>> >>>> If for sprinkler systems, you size the pump based on the >>>> characteristics of the water supply and the system demands. >>>> >>>> >>>> >>>> There are ways to get an estimate on pump size but the final selection >>>> better be verified through hydraulic calculations. >>>> >>>> >>>> >>>> >>>> *Craig L. Prahl* >>>> Fire Protection Group Lead/SME >>>> *CH2M* >>>> 200 Verdae Blvd. >>>> Greenville, SC 29607 >>>> Direct - 864.920.7540 >>>> >>>> Fax - 864.920.7129 >>>> >>>> CH2MHILL Extension 77540 >>>> [email protected] >>>> >>>> >>>> >>>> *From:* Sprinklerforum [ >>>> mailto:[email protected]] *On Behalf Of >>>> *Zachary >>>> Siegrist >>>> *Sent:* Wednesday, May 18, 2016 3:23 PM >>>> *To:* [email protected] >>>> *Subject:* Equation for sizing fire pump >>>> >>>> >>>> >>>> Is there an equation to specify an appropriate pressure when sizing a >>>> fire pump? For example, when sizing gpm, I've always taken the GPM >>>> available at 20 psi divided by 1.5 to give me the maximum GPM rating of the >>>> pump. I'm inquiring to see if such a formula is available to size the >>>> pressure correctly. Can anyone help? >>>> >>>> >>>> >>>> Zach Siegrist >>>> >>>> >>>> >>>> _______________________________________________ >>>> >>>> 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 >> >>
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