Then what if the fire department pushes 150 psi into the siamese? I wouldn't criticize a more conservative method but I would vote for:
Design Area x Design Density x Time Bill Brooks Pittsburgh, PA -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Paul Sincaglia Sent: Tuesday, January 16, 2007 8:51 AM To: [email protected] Subject: RE: NFPA 30 (03ed) - curbs How would you determine the "expected discharge" from the sprinkler system. Dewayne Ahhhh...the loaded question!! First, I have to say you should check your local codes. The IFC requires spill control to handle the largest spill plus 20 minutes of suppression water. However, if you have other performance goals you may need to alter this...but keep in mind that the local code will be your minimum. Now, the fun part and the point that will no doubt spawn debate all day. How do you determine the amount of water you need to retain? I've seen two schools of thought with lots of modifications. The first, simplest, and probably the most common method to do this is to perform your normal hydraulic calculations and simply take the total flow rate produced by the design basis and multiply by the code's 20 minutes. This gives you a volume figure (gallons) and then you size the curbs around the containment area to hold it. Some people include the hose stream allowance, some don't....I say you should include it. However, one always needs to remember that our normal means of doing hydraulic calculations does not calculate actual output. So if you use the calculation method above, you are likely only providing 10-15 minutes of containment. Which brings me to the better alternatives...provided your calculation software has the capability and you have accurate water data. Most hydraulic programs can do what is called a supply calculation. It essentially performs a hydraulic calculation that has no safety factor. i.e. what will the water supply actually push though the pipes if the entire coverage area is flowing. Generally speaking this flow rate is 15-20% higher than your demand calc, but can really be all over the place depending upon your water supply and your base sprinkler design. Now, I generally like this method as it makes a lot of sense to people when you explain how you got your answers. However, as the forum has been kicking about for days now...Hazen-Williams overestimates friction losses at higher pipe velocities. For our normal demand calculations this is no big deal as it provides an additional level of safety in our designs. But in the supply mode, particularly at higher velocities, the fiction loss is overestimated, therefore the water discharge gets underestimated as the flow gets artificially choked by the friction inherent in the Hazen-Williams method. For what it is worth, I personally don't think that the errors in the supply calculation using Hazen-Williams is all that big a deal. However, I have never done any studies or seen any data to support that. I just know that my figures are still slightly lower than what the actual output will likely be IF the entire coverage area where to activate AND the water supply remains the same. So that is how I would handle it...Using the supply calculation method. But I am sure that many others have many other opinions. So let the games begin. So that I can salt the wound a bit....If you are the code consultant, how do you estimate the containment required when no one has even started the sprinkler designs yet? I have my method...What is yours? Now for real work... Paul Sincaglia, P.E. President Firesafety-Solutions, Inc. 440.247.3770 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom L Sent: Monday, January 15, 2007 6:40 PM To: [email protected] Subject: RE: NFPA 30 (03ed) - curbs Dewayne, So do you have a foam system or not? If you do then curbs without drainage is OK If you have a water only system then u will need drainage with the curbs. Review figure 6.8.5 on page 57 of NFPA 30, 2003 edition, it will indicate IF you need to provide spill containment OR liquid spread control. Curbs are used if you have a closed head foam system to control the spread of the product mixed with the water (section 6.4.2.5). If you have a water only sprinkler system and you have a Class I-IIIA liquid then, you need to provide liquid spread control as per 6.8.5.1. Take a look at FM data sheet 7-29 it has more up to date sprinkler protection requirements then NFPA 30/ 2003 edition. Regards Tom Chubb Insurance >From: "Dewayne Martinez" <[EMAIL PROTECTED]> >Reply-To: [email protected] >To: "SprinklerFORUM" <[email protected]> >Subject: NFPA 30 (03ed) - curbs >Date: Mon, 15 Jan 2007 10:51:03 -0600 > >Section 6.4.2.5 deals with curbs, scuppers, special drains, ect....and >states that "If a drainage system is used, it shall have sufficient >capacity to carry the expected discharge of water from the fire >protection systems and hose streams." >If there is only curbs does this apply since there is technically no >drains? If so, what is the proper way to determine the expected >discharge? >Thanks, >Dewayne > >_______________________________________________ >Sprinklerforum mailing list >[email protected] >http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _________________________________________________________________ Type your favorite song. Get a customized station. Try MSN Radio powered by Pandora. http://radio.msn.com/?icid=T002MSN03A07001 _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
