Fire flow is a term and issue not often addressed by A/E and fire protection engineers.
Fire Flow is a requirement within the IFC, Section 507.3 to be specific. There are numerous methods available to use to determine Fire Flow. As the section of Code states, Fire Flow is to be determined by "an approved method". Not all jurisdictions use the same calculation method to determine fire flow. On a new project I will contact the local fire code authority and ask what adopted or approved method is used, then take that method and do the calculations based on the input required. The appendix of the IFC is not always adopted by State law as the body of the Code is so that is why it is not assumed that the Appendix B method is the method for ever instance. But to the point, if the IFC Appendix B method is used, it is a simple chart based on construction type and area of the building. From that you get a required duration and flow rate. This flow rate can be negotiated downward to a lesser rate if the building is sprinklered and if the AHJ allows it to be reduced as defined within the Code. This is not always the case, as I have had AHJ's who know of the hazards present on a site deny the flow rate reduction. So once the flow rate is known we couple with our civil group to size the underground mains and determine the number and arrangement of hydrants needed. We will often take that information and review it with the local fire code official for their buy-in to the concept. Typically there are no real calculations required, more like a bunch of mathematical equations depending on the method used, however we have had to perform hydraulic calculations for specific projects where the AHJ wanted proof the system could deliver the required flow to a particular number of hydrants or the other type was for us to tell the local municipality what flow and pressure we needed at their tie point to satisfy our fire flow demand needs. The requirement of calcs is really rare but I have done them. Hydraulic sprinkler calcs are what we all know them to be, the sprinkler system calculations. No surprises there. But the Fire Flow determination and any associated calculations should not be left up to the sprinkler contractor to determine or perform. The A/E or FPE should have done that as part of the site development. When you see this deferred to the contractor it's most likely because the A/E or whomever developed the package didn't understand or know how to figure this out and it's easier to just put notes on a drawing and make it someone else's problem. It's not been uncommon to see fire flow rates up to 8000 gpm with 2MM gallons of storage for large industrial projects. The challenge there comes when you need to refill the tank in the designated time frame, then the water department begins to choke a bit. Craig L. Prahl Fire Protection Group Lead/SME CH2MHILL Lockwood Greene 1500 International Drive Spartanburg, SC 29303 Direct - 864.599.4102 Fax - 864.599.8439 CH2MHILL Extension 74102 [email protected] -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Brian Harris Sent: Tuesday, December 22, 2015 1:47 PM To: [email protected] Subject: Fire Flow vs Hydraulic calc's Can someone please put into laymen's terms the difference between doing a fire flow demand calc for the underground and the hydraulic calc's for the sprinkler system? We have been running into some projects lately where the civil engineer tries to pawn sizing the underground off onto the sprinkler contractor. I try telling them that's their responsibility not ours but I'd like something more definitive to have on hand. Brian Harris, CET BVS Systems Inc. Sprinkler Division bvssystemsinc.com<http://bvssystemsinc.com/> Phone: 704.896.9989 Fax: 704.896.1935 _______________________________________________ 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
