At 215 psi? Why the high pressure rating? Are you specifying high pressure components on the systems? Relief valves????????
Craig L. Prahl Fire Protection Group Lead/SME JACOBS - 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 Cahill, Christopher Sent: Wednesday, December 20, 2017 11:23 AM To: [email protected] Subject: RE: Multiple Pumps [EXTERNAL] Appreciate the input folks. To my surprise got a response from NFPA faster than expected. "There is nothing in NFPA 20 that prohibits the use of multiple pumps in parallel. Section 4.9.1 is simply saying that the demand cannot exceed 150 percent of the rated capacity of a single pump - this does not mean that you can't use multiple pumps to meet the system demand." We're talking about 3 - 1,500's at 215 psi. One is redundant. In consultation with contractors they thought 3 would be better and cheaper than 2 - 2500's at 215 psi due to long lead time and cost of those not so readily available motors for the bigger pumps. Also, provides better pressure curve being the demand is around 2,500. I agree this isn't typical situation. Well I'm about to do it again soon, so is 3 times in two years typical? Chris Cahill, PE* Associate Fire Protection Engineer Burns & McDonnell Phone: 952.656.3652 Fax: 952.229.2923 [email protected]<mailto:[email protected]> www.burnsmcd.com<http://www.burnsmcd.com/> *Registered in: MN If Americans switched from pounds to kilograms there would be mass confusion. From: Sprinklerforum [mailto:[email protected]] On Behalf Of Matt Grise Sent: Wednesday, December 20, 2017 9:04 AM To: [email protected]<mailto:[email protected]> Subject: RE: Multiple Pumps It seems like this would also introduce more moving parts/valves/etc that would require maintenance and possibly fail. Matt From: Sprinklerforum [mailto:[email protected]] On Behalf Of Prahl, Craig/GVL Sent: Wednesday, December 20, 2017 7:34 AM To: [email protected]<mailto:[email protected]> Subject: RE: Multiple Pumps You could use multiple pumps to achieve the desired flow rate but there would be no advantage in doing so. You would ultimately cost the owner more money in up-front installation costs as well as long term maintenance and inspection costs. I do a lot of large flow facilities where 8,000 -12,000 gpm flow rates are not unusual. You can only achieve those rates with multiple pumps. Typically, those are high risk facilities and there is always one extra pump that acts as a reserve in case one would be out of service. Sometimes we may use a smaller pump (500-1000 gpm) that better reflects the majority of the site's sprinkler demand and make that the primary with the others coming on-line for a large flow event like fire flow or a deluge system. If I had extreme variable flow conditions there are Variable Speed Drives for electric fire pumps. There is no need to try and "throttle" the flow by using multiple small pumps. So basically, just because you can, doesn't mean you should. Craig L. Prahl Fire Protection Group Lead/SME JACOBS - CH2M 200 Verdae Blvd. Greenville, SC 29607 Direct - 864.920.7540 Fax - 864.920.7129 CH2MHILL Extension 77540 [email protected]<mailto:[email protected]> From: Sprinklerforum [mailto:[email protected]] On Behalf Of Cahill, Christopher Sent: Tuesday, December 19, 2017 6:05 PM To: [email protected]<mailto:[email protected]> Subject: Multiple Pumps [EXTERNAL] So I found this in NFPA 20 - 4.9.1 A centrifugal fire pump for fire protection shall be selected so that the greatest single demand for any fire protection system connected to the pump is less than or equal to 150 percent of the rated capacity (flow) of the pump. So does that mean if the demand is 1,000 gpm I can't use 3 - 250 gpm pumps? Don't ask why someone would do that, yes it would be odd. Think really big flows and high pressures where variable flow in reality one might choose to split the pumps. So basically isn't it demanding a single pump for systems up to 7,500 gpm? (assuming a 5,000 gpm pump is the maximum) No option for using 2 - 3,000's? Chris Cahill, PE* Associate Fire Protection Engineer Burns & McDonnell Phone: 952.656.3652 Fax: 952.229.2923 [email protected]<mailto:[email protected]> www.burnsmcd.com<http://www.burnsmcd.com/> *Registered in: MN If Americans switched from pounds to kilograms there would be mass confusion.
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