Not talking about Craig specifics. All John/NFPA provides is great except it should be in AWWA standards not NFPA standards. These people forget the water system originally was a fire protection function to keep the town from burning down. Even today its flows are FP based not domestic. Ask a water guy anything about anything other than GPD and you get a lot of blank stares. You can't adjust if the water utility doesn't know any of the stipulated information.
Chris Cahill, P.E. Fire Protection Engineer Sentry Fire Protection, Inc. 763-658-4483 763-658-4921 fax Email: [email protected] Mail: P.O. Box 69 Waverly, MN 55390 Location: 4439 Hwy 12 SW Waverly, MN 55390 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John Drucker Sent: Monday, November 30, 2009 4:22 PM To: [email protected] Subject: RE: Calcs-How much margin Craig, You've received plenty of comment. Travis and John found the first problem with the design, the code section is 2007 NFPA-13-8.3.4. Before one can decide if the water supply is adequate the system demand must be validated. 22.2.1 provides the required information for water supply, 22.3.5.4 for supply analysis and 23.2.1.2 for determination. 23.2.1.2 provides the answer; "The volume and pressure of a public water supply shall be determined from waterflow test data. An ADJUSTMENT TO THE WATERFLOW TEST DATA TO ACCOUNT FOR daily and seasonal fluctuations, possible interruption by flood or ice conditions, large simultaneous industrial use, future demand on the water supply system, OR ANY OTHER CONDITION THAT COULD AFFECT THE WATER SUPPLY SHALL BE MADE AS APPROPRIATE. As for a prescribed absolute, my understanding pursuant to the standard is supply (properly determined) and demand can match, thus nothing implicitly saying "adjust by 10%". The annex of NFPA-13 does provide insight; A.23.2.1 "Care should be taken in making water tests to be used in designing or evaluating the capability of sprinkler systems. The water supply tested should be representative of the supply that might be available at the time of a fire. For example, testing of public water supplies should be done at times of normal demand on the system. Public water supplies are likely to fluctuate widely from season to season and even within a 24-hour period. Allowance should be made for seasonal or daily fluctuations, for drought conditions, for possibility of interruption by flood, or for ice conditions in winter. Testing of water supplies also normally used for industrial use should be done while water is being drawn for industrial use. The range of industrial-use demand should be taken into account. In special situations where the domestic water demand could significantly reduce the sprinkler water supply,an increase in the size of the pipe supplying both the domestic and sprinkler water can be justified. Future changes in water supplies should be considered. For example, a large, established, urban supply is not likely to change greatly within a few years. However, the supply in a growing suburban industrial park might deteriorate quite rapidly as greater numbers of plants draw more water. Testing of Water Supply. To determine the value of public water as a supply for automatic sprinkler systems, it is generally necessary to make a flow test to determine how much water can be discharged at a residual pressure at a rate sufficient to give the required residual pressure under the roof (with the volume flow hydraulically translated to the base of the riser) - that is, a pressure head represented by the height of the building plus the required residual pressure. The proper method of conducting this test is to use two hydrants in the vicinity of the property. The static pressure should be measured on the hydrant in front of or nearest to the property and the water allowed to flow from the hydrant next nearest the property, preferably the one farthest from the source of supply if the main is fed only one way. For further information on water supply testing, see NFPA-291, Recommended Practice for Fire Flow Testing and Marking of Hydrants. Keep in mind that while NFPA-291 is recommended practice and not a standard it nonetheless has bearing in jurisdictions that include language such; "Any requirement essential for structural, fire or sanitary safety of a building or structure, or essential for the safety of the occupants thereof, and which is not specifically covered by the regulations, shall be determined by the construction official, and appropriate subcode official" (NJAC 5:23-2.2(c)) With that you have more than enough justification to reject this application, as I would. Hope that helps, John Drucker, CET Fire Protection Subcode Official Fire/Building/Electrical Inspector Fire Marshals Office Borough of Red Bank, NJ PS. It's too late once the fire starts. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Monday, November 30, 2009 3:11 PM To: [email protected] Subject: Calcs-How much margin I've got a calc I'm reviewing, after all said and done, 3.63 psi margin between demand and available. Designer used 4.2K heads to get the flow exactly to the decimal of the required flow. This is an industrial type project. With a .15 gpm/sf density at 92 sf per head, the flow would be 13.8 gpm and he's dead on the money. The concern would be that over the years if there was any change in the water supply or decay of the piping, that the operation of half the design area would be questionable. Would you approve or reject this design? Is this cutting it just a bit close? Craig L. Prahl, CET Fire Protection Specialist Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [email protected] http://www.ch2m.com _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
