Right, at the pump for sure, the question is once you get out on the system and there is some pressure losses due to pipe friction and elevations, then you can’t be 1005 sure what pressure the system is actually being subjected to.
Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | [email protected] | www.jacobs.com<http://www.jacobs.com/> From: Sprinklerforum [mailto:[email protected]] On Behalf Of Matt Grise Sent: Wednesday, June 27, 2018 12:13 PM To: [email protected] Subject: RE: [EXTERNAL] RE: Real system pressures versus the calculations My thought is that you don’t need to run a calc at all. If pump-churn plus city-static is greater than 175, there is an over-pressurization problem (at the pump level). Matt From: Sprinklerforum <[email protected]<mailto:[email protected]>> On Behalf Of Prahl, Craig/GVL Sent: Wednesday, June 27, 2018 11:09 AM To: [email protected]<mailto:[email protected]> Subject: RE: [EXTERNAL] RE: Real system pressures versus the calculations Matt, the point is, that when the pump starts it introduces the system to the churn or rated pressure as you state which will decrease as sprinklers open and flow increases. But the point being is that if the calcs reveal a system requirement of 40 psi at the base of the riser, the system does not see just 40 psi if the pump + municipal supply are providing 200 psi to the system. That’s the point of discussion. Without running a Full Flow or Supply calculation you can’t emphatically state there is not a problem with over pressurization based on a Demand calculation alone. Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | [email protected]<mailto:[email protected]> | www.jacobs.com<http://www.jacobs.com/> From: Sprinklerforum [mailto:[email protected]] On Behalf Of Matt Grise Sent: Wednesday, June 27, 2018 11:58 AM To: [email protected]<mailto:[email protected]> Subject: RE: [EXTERNAL] RE: Real system pressures versus the calculations Craig, I don’t quite follow when you ask if the entire system will see pressure over 175. If the pump kicks on at zero flow (perhaps the jockey fails). The entire system will be subjected to the city static pressure plus the pump churn pressure. Any component that is higher in elevation will see less pressure than the lower components due to elevation changes. In that sense – the various elevations of piping would never see the same pressure (without some pressure regulating equipment at various levels). As the flow rate increases, each pressure source (the city supply and the fire pump) will have less pressure to give – so the entire system will be exposed to less pressure as the flow increases. I am not sure we have enough information to say what actual pressure will occur at various floor levels. Matt From: Sprinklerforum <[email protected]<mailto:[email protected]>> On Behalf Of Prahl, Craig/GVL Sent: Wednesday, June 27, 2018 10:34 AM To: [email protected]<mailto:[email protected]> Subject: RE: [EXTERNAL] RE: Real system pressures versus the calculations Oh I am very well aware of the issue, I’d just like to be sure I’m not the only one who has an understanding of what our typical calculations represent. I sometimes gasp at the lack of understanding of design and calculations on the part of some designers. Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | [email protected]<mailto:[email protected]> | www.jacobs.com<http://www.jacobs.com/> From: Sprinklerforum [mailto:[email protected]] On Behalf Of MFP Design, LLC Sent: Wednesday, June 27, 2018 11:29 AM To: [email protected]<mailto:[email protected]> Subject: [EXTERNAL] RE: Real system pressures versus the calculations What if fewer sprinklers open than in your design area? The pump and water supply aren’t going to know what the minimum sprinkler demand is and magically hold to that point while discharging no more. I know you are well aware of this. The sprinkler calculations are demand calcs that give minimums. You can run supply calcs to determine what pressures and flows you can expect with the full water supply discharging. [MFP_logo_F] Travis Mack, SET MFP Design, LLC 3356 E Vallejo Ct Gilbert, AZ 85298 480-505-9271 fax: 866-430-6107 email:[email protected]<mailto:email:[email protected]> http://www.mfpdesign.com<https://urldefense.proofpoint.com/v2/url?u=https-3A__na01.safelinks.protection.outlook.com_-3Furl-3Dhttp-253A-252F-252Fwww.mfpdesign.com-252F-26data-3D02-257C01-257C-257C1121d49f9e6b4cf248f108d4df580e77-257C14e5497c16da42e69ffa77d19bafe511-257C0-257C0-257C636379016677342180-26sdata-3DHJ8OA4xyeHAoxXNz5mu-252FYfycgtd5nsFrrpvzulZiNkQ-253D-26reserved-3D0&d=DwMFaQ&c=OgZOSER8c1RLeytEexU279Q2qk0jVwkrOdYe5iSi-kk&r=6qYbbLx8x0UrMujmEGNoh-2hzoFD2d1EB5d2sQF0_OI&m=TLFSl1U9Qj0s0yFLejZ21gAPh9nu1h7UpvICxkhX_dQ&s=pYdJeOIw4WA2kkFCOSYa1aNAei-lXMc_HM803l32t0M&e=> https://www.facebook.com/pages/MFP-Design-LLC/92218417692<https://urldefense.proofpoint.com/v2/url?u=https-3A__na01.safelinks.protection.outlook.com_-3Furl-3Dhttps-253A-252F-252Fwww.facebook.com-252Fpages-252FMFP-2DDesign-2DLLC-252F92218417692-26data-3D02-257C01-257C-257C1121d49f9e6b4cf248f108d4df580e77-257C14e5497c16da42e69ffa77d19bafe511-257C0-257C0-257C636379016677342180-26sdata-3DH-252BwdcgK8DLGBcNoqJEvUrzsXngySwkX56Vgf9gM9EGk-253D-26reserved-3D0&d=DwMFaQ&c=OgZOSER8c1RLeytEexU279Q2qk0jVwkrOdYe5iSi-kk&r=6qYbbLx8x0UrMujmEGNoh-2hzoFD2d1EB5d2sQF0_OI&m=TLFSl1U9Qj0s0yFLejZ21gAPh9nu1h7UpvICxkhX_dQ&s=xYD61-mBUk4UGQElrG_ZKAypPmH-63Ay347ffUHEDdY&e=> Send large files to us via: https://www.hightail.com/u/MFPDesign<https://urldefense.proofpoint.com/v2/url?u=https-3A__na01.safelinks.protection.outlook.com_-3Furl-3Dhttps-253A-252F-252Fwww.hightail.com-252Fu-252FMFPDesign-26data-3D02-257C01-257C-257C1121d49f9e6b4cf248f108d4df580e77-257C14e5497c16da42e69ffa77d19bafe511-257C0-257C0-257C636379016677342180-26sdata-3DeGdMZGu2wXhUupGwgGTrqF3b54OP5-252BAZvlHhABSexWY-253D-26reserved-3D0&d=DwMFaQ&c=OgZOSER8c1RLeytEexU279Q2qk0jVwkrOdYe5iSi-kk&r=6qYbbLx8x0UrMujmEGNoh-2hzoFD2d1EB5d2sQF0_OI&m=TLFSl1U9Qj0s0yFLejZ21gAPh9nu1h7UpvICxkhX_dQ&s=EyHQEus8jlDBFxZsja9uToA7nCKvhYLFeMIULfrhnX0&e=> LinkedIn: https://www.linkedin.com/in/travismack<https://urldefense.proofpoint.com/v2/url?u=https-3A__na01.safelinks.protection.outlook.com_-3Furl-3Dhttps-253A-252F-252Fwww.linkedin.com-252Fin-252Ftravismack-26data-3D02-257C01-257C-257C1121d49f9e6b4cf248f108d4df580e77-257C14e5497c16da42e69ffa77d19bafe511-257C0-257C0-257C636379016677342180-26sdata-3DtT5E7LsZjSmyreKi4gDCa70EWN-252BZodi-252FhbeCbHNRijI-253D-26reserved-3D0&d=DwMFaQ&c=OgZOSER8c1RLeytEexU279Q2qk0jVwkrOdYe5iSi-kk&r=6qYbbLx8x0UrMujmEGNoh-2hzoFD2d1EB5d2sQF0_OI&m=TLFSl1U9Qj0s0yFLejZ21gAPh9nu1h7UpvICxkhX_dQ&s=kaKtfZQLNwhRlGJkqbhIKQMGXnFx83VbOLUlPhMK6FA&e=> “The bitterness of poor quality remains long after the sweetness of low price is forgotten.” From: Sprinklerforum <[email protected]<mailto:[email protected]>> On Behalf Of Prahl, Craig/GVL Sent: Wednesday, June 27, 2018 8:22 AM To: [email protected]<mailto:[email protected]> Subject: Real system pressures versus the calculations I have a system that was originally designed with a fire pump taking suction from an elevated municipal water tank. At some point in time the system source was changed from the tank to a municipal water supply. This change has resulted in the system pressures being well over 200-250 psi. So far nothing has blown out, yet but numerous buildings and underground were built based on standard pressure rated components. The thought for the day is this, when you run a calculation, the output will show the minimum required pressure at the hydraulically most remote sprinkler that is required to provide the design flow rate. The calculations also show the deviation between Required and Available system pressures. So, when the fire pump kicks on, what the system ACTUALLY sees is the rated pressure of the pump being introduced into the system, not the minimum required pressure that is shown in the calculations, Agreed? If it is stated that in the calculations that the pressure at the sprinklers on an upper floor will be less than 175 psi but those on the lower floor will be greater is it safe to assume based on the ACTUAL pressures coming out of the pump that the entire system will likely see pressures exceeding 175 psi? Looking for some thoughts. Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | [email protected]<mailto:[email protected]> | www.jacobs.com<http://www.jacobs.com/> ________________________________________________________________________________________ NOTICE - This communication may contain confidential and privileged information that is for the sole use of the intended recipient. Any viewing, copying or distribution of, or reliance on this message by unintended recipients is strictly prohibited. If you have received this message in error, please notify us immediately by replying to the message and deleting it from your computer.
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