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 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] <javascript:_e(%7B%7D,'cvml','[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] <javascript:_e(%7B%7D,'cvml','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] <javascript:_e(%7B%7D,'cvml','[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] <javascript:_e(%7B%7D,'cvml','[email protected]');> From: Sprinklerforum [mailto:[email protected] <javascript:_e(%7B%7D,'cvml','[email protected]');> ] On Behalf Of Zachary Siegrist Sent: Wednesday, May 18, 2016 3:42 PM To: [email protected] <javascript:_e(%7B%7D,'cvml','[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] <javascript:_e(%7B%7D,'cvml','[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] <javascript:_e(%7B%7D,'cvml','[email protected]');> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] <javascript:_e(%7B%7D,'cvml','[email protected]');> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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