Steve, Thanks for your reply and your kind trying to understand me. I know it’s difficult for you to state what is not complied to NFPA.
Tehran Fire Department, as the only AHJ, allows 3500GAL in light hazard occupancies and if QR sprinklers are used, they allow 2500GAL water tank. As the buildings are not connected to city main, they have difficult time providing the space for big water tanks. When it comes to water tank size, as NFPA is requesting too much, they try to somehow comply to European codes. Check EN12845 which is used in Europe, page 47, requesting 11 cubic meter (2900GAL) water tank for light hazard occupancies. http://sarian.ir/EN12845.pdf Maybe, the “Risk Acceptance Level”, infrastructure and local economy play an important role in their decision and maybe just ignorance!. We all know that most of the fires in light hazard occupancies like residential and office buildings are extinguished with less than 3 activated sprinklers. So maybe they calculate the system based on 3 operated sprinklers and they accept the risk. VdS standard in Germany is also considering 4 activated sprinklers. Most European cities are also not connected to city main water. http://sarian.ir/VdSCEA4001en.pdf Considering all mentioned differences between how Americans vs. Europeans think about sprinkler design, I am thinking to find a solution to somehow cover some of the weaknesses in our design here in Iran. Best, Reza www.sarian.ir <http://www.sarian.ir/> Reza: I understand your earnest interest in finding a solution, but what you’ve done is pose questions to the Forum and not fully informed of all conditions, which compromises us who may answer. For example, the idea that you’re “limited” to a 3,500 gallon water tank is an arbitrary figure and simply ridiculous. Who is limiting this? If you’ve been told to proceed with system design and not been given the resources to design or install a tank of adequate capacity, then that is a DEFICIENCY and outside the scope of the NFPA standards. So the first correspondence should be a letter to whoever is specifying or “limiting” the tank capacity to inform them that it needs to be the appropriate capacity. And I’m failing to grasp what a restrictor gets you in any case. If the hazard group is Light, your duration requirement (with electronic monitoring of your system) is 30 minutes; for Ordinary it’s 60 minutes. Using your theoretical demand with restrictor of 314 GPM + 100 PSI hose allowance, you have to prove 414 GPM for 30 or 60 minutes, no? So you need a tank with 12,420 or 24,840 usable gallons capacity. Nominal reduction of the sprinkler demand isn’t and adequate solution. It seems to me that with a deficiency of such extraordinary magnitude you want the first two or three sprinklers to work as well and reliably as possible, which means forget the restrictor. I’ll leave it to you to determine who to resolve your water supply duration problem, but if this was in the USA it would be a non-starter. My opinion only, SML From: Sprinklerforum [mailto:[email protected]] On Behalf Of Reza Esmaeili Sent: Thursday, February 09, 2017 8:57 AM To: [email protected] Subject: RE: Reducing Sprinklers' Pressure in a Combined Standpipe/Sprinkler System Thanks for your replies David and Art. To Steve: Installing a restrictor to lessen the flow at sprinklers is not just for reducing pump size to save a few Dollars. It’s also about the water tank size. Our buildings are not connected to the city main like yours and we have to rely on a small water tank size around 3500GAL. If I don’t reduce the sprinkler system flow, the water tank is finished in less than 7 minutes. To Art: At first I was also thinking of reducing the size of main pipe to the sprinklers to hydraulically reduce pressure/flow (instead of installing a restrictor just at the beginning). But it seems in this way, the pressure drop is very vulnerable and very related at where the sprinklers are going to be activated. Imagine I reduce 3” to 2” and the main pipe lenght to the most remote sprinkler is 120ft. - If 12 most remote sprinklers are activated (120ft from the riser), the pressure behind the sprinklers is around 20psi, so the total flow is around 320GPM. - If 12 sprinklers in the middle are activated (60ft from the riser), the pressure behind them is around 40psi, so the total flow is around 420GPM. I want to say when you are going to reduce the pressure in a pipe length, you are not sure when the sprinklers are going to operate. At the end of pipe, in the middle or at the first? So you are not sure how much the pressure if going to drop. But if you are installing a reducer just at the beginning, you suddenly drop the pressure and no matter where there sprinklers are going to operate. Best, Reza www.sarian.ir <http://www.sarian.ir/> I suggest you reduce pipe size on the main run to increase pressure and reduce the flow hydraulically. You should be able to balance flow and pressure with the proper pipe sizes. Art Tiroly ATCO Fire Protection. From: Sprinklerforum [mailto:[email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> ] On Behalf Of Reza Esmaeili Sent: Thursday, February 09, 2017 10:50 AM To: [email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> Subject: RE: Reducing Sprinklers' Pressure in a Combined Standpipe/Sprinkler System Thanks for your reply Steve. * The local code requires 100gpm@65psi <https://mg.mail.yahoo.com/neo/b/compose?to=100gpm@65psi> for the hydraulically most remote hose connection which are class II 1 1⁄2 in hose stations. Both hose stations and sprinklers are connected to a single wet pipe riser. The pumps should be selected based on sprinklers demand + standpipe demand. The local code ask to simply add 100 gpm to sprinkler demand. For example, if sprinkler demand is 400gpm, just add 100 gpm for standpipe. These 1 1⁄2 in hose stations are not for occupant use and not small hose connections as stated in NFPA 13. Fire fighters in my country use 1 1⁄2 connections, not 2 1⁄2. * The city water main is not able to supply the demand, so a private water tank, located in the basement is supplying both the sprinklers and standpipe. * Travis also suggested using 4.2k sprinklers which is a good idea, but there are some problems. First the water is not clean for such a small orifice. Second 4.2k is not available in our market! * As each sprinkler is covering 130 sq.ft, and the required density is 0.15, so the minimum required flow for each 5.6K sprinkler is 19.5GPM. That is to say 13psi is the minimum pressure at the most remote sprinkler. After installing the restrictor, the minimum pressure is 21psi which is ok. Coming back to the original question: Am I allowed to install a restrictor? For example, if the main sprinkler pipe at each floor is 3", can I install a short 1" pipe just at the beginning to reduce sprinklers pressure? This 0.5m length, 1" pipe can suddenly drop the pressure from 65psi to 30psi. Then the most remote sprinkler pressure at the top floor would be around 20psi which I like. If required, the more I get nearer to the pump located at the basement, I have higher pressure, and I can cut more pressure using this small pipe. For example if the pressure behind the hose station at the ground floor is 110psi, I can use a 2m length, 1" pipe just at the beginning of the pipe supplying the sprinklers to drop the pressure from 110psi to 20psi. Do you see any problems? Best, Reza www.sarian.ir <http://www.sarian.ir/> From: Reza Esmaeili [mailto:[email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> ] Sent: Thursday, February 9, 2017 6:29 PM To: '[email protected]' Subject: RE: Reducing Sprinklers' Pressure in a Combined Standpipe/Sprinkler System Hi Craig, Travis, Scot and Tim, Thanks for your replies. I am using Pipenet Spray/Sprinkler software which is mainly a hydraulic colocation software not used in the US. You are right Craig, when less sprinklers are activated, the restrictor can't lessen the pressure, but in this case I have low flow because of less opened sprinklers. Look at the below scenarios. The first scenario is without restrictor and the second and third are with restrictor. If I don't install a restrictor, my sprinkler system demand is 451gpm. But if I install a restrictor, my maximum sprinkler system demand is 314gpm. 1- First scenario: No restrictors, 12 sprinklers activated at the most remote area at the top floor: - The pressure at the beginning of sprinkler piping: 65psi - The pressure just behind the most remote sprinkler: 45psi - Total flow for all 12 open sprinklers: 451gpm 2- Second scenario: 0.5m length, 1” pipe, 12 sprinklers activated at the most remote area at the top floor: - The pressure at the beginning of sprinkler piping: 65psi - The pressure after restrictor: 31psi - The pressure just behind the most remote sprinkler: 21psi - Total flow for all 12 open sprinklers: 314gpm 3- Second scenario: 0.5m length, 1” pipe, 3 sprinklers activated at the most remote area at the top floor: - The pressure at the beginning of sprinkler piping: 67psi - The pressure after restrictor: 61psi - The pressure just behind the most remote sprinkler: 56psi - Total flow for all 3 open sprinklers: 127gpm Best, Reza Cel: +98 9122444875 www.sarian.ir <http://www.sarian.ir/> Here’s a question, are you going to try to reduce the sprinkler system pressure to lessen the flow based on one sprinkler or two or ten flowing? If you base it on ten but only have three flowing, your pressure reduction does not work the same. The sprinkler demand we calc to prove is a product of required pressure and K-factor not provided pressure and K-factor. Your calcs are to prove the system works based on the supply pressure and flow. Every sprinkler system design will typically flow more than what is calculated since we are only proving the supply can meet the minimum design requirements. We calculate a 1500 sq. ft. area and find a required flow and pressure to accomplish that. But when only one or two sprinklers flow and the supply flow and pressure to that system are the same as when we calculated 10 or 12 sprinklers, the discharge from a few will always be more than what is needed. Also, actual flow, even for the entire remote area will be more than the minimum calculated if there was any cushion in your calcs. What calculation software are you using? Basically, calculate what is required for the sprinklers, then calculate the standpipe and do not worry about the overage on the sprinkelrs. Craig L. Prahl Fire Protection Group Lead/SME CH2M 200 Verdae Blvd. Greenville, SC 29607 Direct - 864.920.7540 Fax - 864.920.7129 CH2MHILL Extension 77540 [email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> From: Sprinklerforum [mailto:[email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> ] On Behalf Of Reza Esmaeili Sent: Thursday, February 09, 2017 7:05 AM To: [email protected] <https://mg.mail.yahoo.com/neo/b/[email protected]> Subject: Reducing Sprinklers' Pressure in a Combined Standpipe/Sprinkler System [EXTERNAL] Hi forumites, As per NFPA 14, in a combined standpipe/sprinkler system, the minimum pressure at the outlet of most remote 1 1⁄2 in. hose station should be 65psi. As standpipe and sprinkler riser in shared, I want to reduce the pressure to the sprinklers to around 15psi in order to reduce the total sprinklers flow demand and finally to select a smaller fire pump. What is the most cost-effective way to do that? Can I use a restrictor? For example, if the main sprinkler pipe at each floor is 3", can I install a short 1" pipe just at the beginning to reduce sprinklers pressure. Can I do that? I checked this in a hydraulic calculation software and in works fine, but I am not sure if this is a right way. Best, Reza www.sarian.ir <http://www.sarian.ir/>
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