NFPA-25 only applies to ITM, NFPA-20 applies to initial design and acceptance.
In that regard; 2007 NFPA-20 14.2.7.2.2 applies to Field Acceptance Test Procedures, the testing provisions don't justify nor negate the general requirements. Preceding 14.2.7.2.2 of the standard is 5.14.3.1, 3.2 & 3.3, the general requirements, specifically the sizing of suction piping. Keep in mind that 14.2.7.2.2 was not intended to do away with the 150% flow requirement and the piping sizing requirements but rather to address situations where the available water supply such as a city water main was capable of delivering system demand but incapable of delivering 150%. Even if the available water supply is incapable of 150% delivery according to the standard the suction piping must sized to do so. Frankly it's a design issue. A properly sized pump is available and would satisfy the requirements of the standard. Sincerely, John Drucker Fire Protection Subcode Official (AHJ) New Jersey -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, November 07, 2008 10:18 AM To: [email protected] Subject: Re: Fire Pump Suction NFPA 25 2008, 8.3.3.1.1 If the available suction supplies do not allow flowing of the pump at 150 percent, flow at maximum. Sent from my BlackBerry Smartphone provided by Alltel -----Original Message----- From: "Fletcher, Ron" <[EMAIL PROTECTED]> Date: Fri, 7 Nov 2008 07:35:48 To: <[email protected]> Subject: RE: Fire Pump Suction What's the problem? Test the pump at 100% capacity and quit. 14.2.7.2.2 If available suction supplies do not permit the flowing of 150 percent of rated pump capacity, the fire pump shall be operated at maximum allowable discharge to determine its acceptance. This reduced capacity shall constitute an acceptable test, provided that the pump discharge exceeds the fire protection system design flow and pressure requirements. Ron Fletcher Aero Automatic Phoenix, AZ P.S. Todd, sounds like that hospital was designed for 3 manual wet standpipes and the 250 gpm pump is there to supply the sprinkler systems. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Drucker Sent: Friday, November 07, 2008 7:10 AM To: [email protected] Subject: RE: Fire Pump Suction As the saying goes bigger is not always better. Sadly I hang my head when I hear where was the EoR. John Drucker Fire Protection Subcode Official (AHJ) New Jersey -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Todd Williams - FPDC Sent: Friday, November 07, 2008 8:19 AM To: [email protected] Subject: RE: Fire Pump Suction It's nice to see that I don't get all of this stuff to figure out. I wonder where the EoR was on this project? I also love the term "had access". Is this a pump he mis-ordered for another job and got stuck with? If this were my crisis, I would run a test increasing the flow in 100 gpm increments until I got to the -3 suction. That would give me what I can run the pump to flow wise. Assuming you hit the -3 before the 600 gpm, you essentially have three choices: install the correct pump, change out the suction line or come up with a way to live with the existing situation. This would probably include discussions with the owner, pump rep and the AHJ. Best of luck. I am working on a hospital with a 250 gpm pump that is trying to feed 3 standpipes. I'll let you know when this pump becomes available (just kidding) At 11:58 PM 11/6/2008, you wrote: >The concern is the size of the suction pipe. The pump selected was 250 gpm, >to match the 222 gpm, 40 psi demand. But the contractor had access to a 400 >gpm, 70 psi pump which got installed instead. An overkill, but that is what >happened. The suction piping from the tank to the pump is 4". The engineer >is pointing to NFPA 20, 2003 section 5.14.3.2 which requires gauge pressure >at pump suction flange to be no less than -3 psi. Although the flow is not >mentioned in this particular section, from section 5.14.3.1 it can be >deduced that it is 150% of the rated flow. Now flowing 600 gpm through the >4" suction piping and avoiding cavitation is the problem. > >Tony > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Chris Cahill >Sent: November 6, 2008 1:59 PM >To: [email protected] >Subject: RE: Fire Pump Suction > >If I understand your concern you are worried the tank will run out before 30 >minutes because of overflow due to a supply calc vs. a demand calc. You are >worried about calc'ed world vs. real world. Fine but in what real world >will the actual design area operate. Odds are you won't be in the remote >area which increases overflow meaning less than 33 minutes. Odd are less >than the calc'ed number of heads will flow decreasing the demand meaning >more than 33 minutes. Odds are 2 heads (or less) will flow and you won't >have anywhere near 222 gpm coming out. This probability is the driving >force showing in reality the tank will last more than 33 minutes. > >Overflow is good from a fire suppression standpoint anyway. More water per >time equals higher probability of suppression and quicker time. It's also >not linear, you get more bang for the buck with increase in density. I >don't know of specific figures, just going from experience. If you put the >fire out in 10 minutes and the tank runs dry in 20 is there a problem? > >IMHO the system failed if the full remote area operates in the first place. >Or at least a serious investigation is warranted to determine why. If you >still need the sprinklers after about 10-15 minutes there is a problem. The >extra heads and 30 minutes already have a deal of safety in them. > >The actual produced is always a balance between flow and available pressure. >So yes if the entire remote area opens you will in reality drain the tank >faster than 33 minutes. Could be much quicker depending on the shape of the >pump curve and the overflow. But assuming you are light hazard based on the >very little information provided I don't see a problem. If you are really >curios start running system supply calc's for different areas and you should >see the tank will never last 33 minutes with a full sized calc'ed area and >much longer when less than the full area. > >Now maybe you are 45 minutes from the closest FD and this becomes an >engineering question to consider. Some day the code may differentiate >between available levels of fire service but not yet. > >But hey maybe I missed the point of your question. > >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 A.P.Silva >Sent: Thursday, November 06, 2008 2:11 PM >To: [email protected] >Subject: RE: Fire Pump Suction > >The maximum sprinkler demand as per hydraulic calcs. is 222 gpm. The water >supply is by means of storage tanks having a total volume of 7448 gallons. >Just barely enough for approx. 33 minimute at maximum demand. The contractor >has installed a 400 gpm fire pump. NFPA 20 requires gauge pressure at the >fire pump suction flange to be 0 psi or higher when pump is operating at >150% of rated flow, which in this case is 600 gpm. Is this realistic? I >know, if the suction pressure is 0 psi or higher for 600 gpm flow, it will >work for all cases. However, I would expect a flow between the supply and >demand with all design sprinklers flowing. Anyone with experience with >pumps, care to comment? > >Tony > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of Joe Hankins >Sent: November 4, 2008 8:56 AM >To: [email protected] >Subject: Re: Fire Pump Suction > > Boiling (cavitation) starts starts when the water pressure at the impeller >is reduced to the vapor pressure of water at the water temperature. You see >this addressed in the pump literature as "NPSH" >The term net positive suction pressure (NPSH) is defined as the difference >between the suction pressure and the vapor pressure of water and must be a >positive number to avoid cavitation. At 68 degrees F water temperature, the >vapor pressure is 0.35 psi. So, as long as the inlet pressure is greater >than 0.35 psi absolute or -14.3 gauge, no cavitation. > >In practical terms, so long as the suction pressure is above -12 to -13 psi, >you should be fine. When a typical centrifugal fire pump starts to >cavitate, you'll know it. (sounds like the pump is full of rocks), and >you're not going to damage the pump unless you let it cavitate for an >extended period of time. The problem, of course, is that the pump >performance deteriorates significantly. > >Joe > > > >_______________________________________________ >Sprinklerforum mailing list >http://lists.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 >http://lists.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 >http://lists.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 >http://lists.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) Todd G. 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