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NFPA 13 Clause 12.5.1 1
- Thread starter DTR1968
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TravisMack
Mechanical
30% increase shall be applied to dry and double interlock systems. Single interlock preaction does not get the 30% penalty. The idea is that with a single lock, there will be water to the sprinkler by the time it activates. The dry and DI systems have a time delay up to 60 seconds getting water to the sprinkler after activation. That is the reason for anticipation of more sprinklers operating.
Travis Mack
MFP Design, LLC
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Travis Mack
MFP Design, LLC
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TravisMack
Mechanical
NFPA 13, 2013 EDITION
11.2.3.2.5* Dry Pipe and Double Interlock Preaction Systems.
For dry pipe systems and double interlock preaction systems, the area of sprinkler operation shall be increased by 30 percent without revising the density.
Note that it only says double interlock systems and does not reference single or non-interlock.
Travis Mack
MFP Design, LLC
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11.2.3.2.5* Dry Pipe and Double Interlock Preaction Systems.
For dry pipe systems and double interlock preaction systems, the area of sprinkler operation shall be increased by 30 percent without revising the density.
Note that it only says double interlock systems and does not reference single or non-interlock.
Travis Mack
MFP Design, LLC
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skdesigner
Mechanical
Travis - given that the OP is referencing chapter 12 (I'm assuming that means we're talking about high piled storage), would 12.5.1 not modify the provisions of 11.2.3.2.5 in a storage occupancy and therefore require the 30% increase for all three types of preact system in accordance with 11.1?
If it's not a storage occupancy, then I agree wholeheartedly - 30% increase only for dry and DIPA.
R M Arsenault Engineering Inc.
If it's not a storage occupancy, then I agree wholeheartedly - 30% increase only for dry and DIPA.
R M Arsenault Engineering Inc.
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1
- #7
Below is from the NFPA 13 handbook regarding the section 12.5.1
The design area must be increased for single interlock preaction systems. The situation pro- tecting storage occupancies is different from the situation protecting light, ordinary, or extra hazard systems. For light, ordinary, and extra hazard systems, Chapter 11 does not require the increase of 30 percent for single interlock preaction systems. But for storage occupancies, Chapter 12 requires the increase for single interlock systems to ensure that the water will be at the sprinkler when the sprinklers open. Getting water to the sprinklers in the single interlock preaction system is a function of the sensitivity of the detection system. The detection system must be fast enough to overcome the water transit time from the preaction valve to the open sprinkler, so there will not be a delay in getting water to the fire. With the rapid fire growth rate associated with storage occupancies, any delay will result in additional sprinklers open- ing. Therefore, every preaction system, including single interlock systems, needs to have a 30 percent increase to the design area.
In theory, a single interlock preaction system could be designed with very sensitive detec- tors that could start the flow of water early enough that, by the time that sprinklers open, water would be at the sprinklers. If a designer could provide calculations and demonstrations (once the system was finished) to ensure this, it is possible that the 30 percent design area increase would not be necessary. This would need to be evaluated by all of the authorities having jurisdiction on the job, and they would need to agree that the design area increase would not be needed under one of the equivalent performance sections of NFPA 13 (Section 1.5 or 1.6).
The design area must be increased for single interlock preaction systems. The situation pro- tecting storage occupancies is different from the situation protecting light, ordinary, or extra hazard systems. For light, ordinary, and extra hazard systems, Chapter 11 does not require the increase of 30 percent for single interlock preaction systems. But for storage occupancies, Chapter 12 requires the increase for single interlock systems to ensure that the water will be at the sprinkler when the sprinklers open. Getting water to the sprinklers in the single interlock preaction system is a function of the sensitivity of the detection system. The detection system must be fast enough to overcome the water transit time from the preaction valve to the open sprinkler, so there will not be a delay in getting water to the fire. With the rapid fire growth rate associated with storage occupancies, any delay will result in additional sprinklers open- ing. Therefore, every preaction system, including single interlock systems, needs to have a 30 percent increase to the design area.
In theory, a single interlock preaction system could be designed with very sensitive detec- tors that could start the flow of water early enough that, by the time that sprinklers open, water would be at the sprinklers. If a designer could provide calculations and demonstrations (once the system was finished) to ensure this, it is possible that the 30 percent design area increase would not be necessary. This would need to be evaluated by all of the authorities having jurisdiction on the job, and they would need to agree that the design area increase would not be needed under one of the equivalent performance sections of NFPA 13 (Section 1.5 or 1.6).
TravisMack
Mechanical
Woah!! Read through that way too fast. Yes, referencing Chapter 12 changes everything. I just saw preaction and immediately jumped to no increase on single interlock.
But, yes, for storage you MUST increase the 30%.
Travis Mack
MFP Design, LLC
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But, yes, for storage you MUST increase the 30%.
Travis Mack
MFP Design, LLC
"Follow" us at
- Thread starter
- #10
Guys,
Thank you all for the feedback, it's all good stuff,very informative and has helped me to understand my situation a lot better, I can now see where the Consultant I am dealing with is coming from.
However...
The Single Interlock pre Action System I am looking at is at Roof Level above an MSW Storage Bunker/Pit on an Energy from Waste Plant, the Bunker is protected with a specified SIPA Sprinkler System in line with NFPA 850 9.3.3.2.1 to protect against Structural Damage with 2 No. Water Monitors as per NFPA 850 9.3.3.2.2 also covering the MSW Bunker/Pit.
There are also Hose Stations located around the MSW Pit/Bunker.
The detection devices for the SIPA Sprinklers are Flame Detectors.
The depth of the Bunker/Pit is 65 feet and from the very top level of the Bunker/Pit the Sprinklers another 35 Feet, so this begs the question for me...is 12.5.1 clause relevent for this application?
Based on the comments by LCREP regarding high piled storage and the rapid fire growth associated with storage occupancies, 12.5.1 does not fit for me.
Your thoughts would be appreciated.
Thanks
Dave
Thank you all for the feedback, it's all good stuff,very informative and has helped me to understand my situation a lot better, I can now see where the Consultant I am dealing with is coming from.
However...
The Single Interlock pre Action System I am looking at is at Roof Level above an MSW Storage Bunker/Pit on an Energy from Waste Plant, the Bunker is protected with a specified SIPA Sprinkler System in line with NFPA 850 9.3.3.2.1 to protect against Structural Damage with 2 No. Water Monitors as per NFPA 850 9.3.3.2.2 also covering the MSW Bunker/Pit.
There are also Hose Stations located around the MSW Pit/Bunker.
The detection devices for the SIPA Sprinklers are Flame Detectors.
The depth of the Bunker/Pit is 65 feet and from the very top level of the Bunker/Pit the Sprinklers another 35 Feet, so this begs the question for me...is 12.5.1 clause relevent for this application?
Based on the comments by LCREP regarding high piled storage and the rapid fire growth associated with storage occupancies, 12.5.1 does not fit for me.
Your thoughts would be appreciated.
Thanks
Dave
MatthewJWillis
Mechanical
I don't know what MSW is, but I did read the word storage after it in the description.
Based on this, and this alone, I feel 12.5.1 Does apply.
If this is storage then Chapter 12 is the playground. What level of storage is a different animal...
R/
Matt
Based on this, and this alone, I feel 12.5.1 Does apply.
If this is storage then Chapter 12 is the playground. What level of storage is a different animal...
R/
Matt
MatthewJWillis
Mechanical
I looked up MSW.
If it is as described in 850, then you have one of the fastest developing fires around.
CDAFD is right on the money. 13 is not meant to protect these...
If it is as described in 850, then you have one of the fastest developing fires around.
CDAFD is right on the money. 13 is not meant to protect these...
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