AS Hydraulic cals for Large DC's

[WallyFP]

Hi,

Are hydraulic calculations required for every sprinkler system in a large Distribution Center (or similar) where there are many systems, each having the same designs and piping layouts. I seem to see more and more submittals where only the most remote system (furthest from the water supply) is calc'd then that demand is put on all placards. Systems are generally very similar but are not always identical - some are smaller than others which would likely result in a lower demand (assuming the same design). I know that if the supply is adequate for the most remote system, then it would be okay for closer systems, but I would rather see calcs for each system but I can't find a reference in NFPA or FM that provides clarification. Maybe they're not necessary?

Thanks for your time,

Wally

 

[cdafd]

I would require calcs on each system

Not sure if 13 would address this situation

 

[WallyFP]

Thanks Cdafd. Glad that to hear that I'm not the only one that thinks that way. If anyone else can reference a Code section, that would help as well.

 

[Sdpaddler50]

Wally, i have worked on quite a few large DC's in my area over the years. My job is to specify the overall fire system protection criteria, which includes the sprinkler design based on the commodity, storage configuration, etc. I only run calcs on rare occassions, and not for final design. Anyway, when i review plans, the contractors always give the MRA calc for each system. The submitall package therefore has the prints, and then the calcs for each system, plus the material submitall. The hydraulic design placard on each riser is similar, but different for reasons you note. I would think you should be able to find the actual code notation in 13.

 

[stookeyfpe]

Oh I love this. I've seen DCs with 38 foot ceilings storing Class IIIB liquids in which the only valid designs was based on 30 foot ceilings. The same with aerosols. The calculations help in confirming the design. I've found competing designs areas which lead to other issues.

 

[LCREP]

From NFPA 13 2011 Ed, this has been part of NFPA 13 for many years.

Chapter 23 23.1* Working Plans.
Plans and Calculations
23.1.1* Working plans shall be submitted for approval to the authority having jurisdiction before any equipment is installed or remodeled.

(34) Hydraulic reference points shown on the plan that correspond with comparable reference points on the hydraulic calculation sheets.

How can you comply with the above section by only submitting a few calculations?

One of the 1st things I do in the plan review process is make sure I have calculations for each system, if not, I reject and referance the above section.

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for information.

 

[MGXFP]

You should calculate each system naturally. You might even be able to use less pipe material on systems closer to the risers and save some money.

 

[WallyFP]

Thanks to all for the replies. Areas with aerosols, 3B's, and other hazards outside the given storage commodity are always calculated separately, but not always the typical Class III / IV commodities when many identical systems. I agree that ALL should be. I really like the idea of the general information placards per Section in NFPA 13 and as Stookeyfpe noted in his Coffee Break document. I completely agree that it is the changes in occupancy over time (often very slow)and not knowing what can / can't be protected by existing designs that creates the unrecognized deficiencies. The Grand Prairie Paddock Whse fire was a perfect example! Thanks again for your comments.

Wally

 

[TravisMack]

I have never been asked to provide calculations for each system. We just finished a large warehouse (1.2M sq ft) and did not calculate every system. Typically, we calculated the most remote system and then sized the others based on that. When the systems were significantly different, then we provided calculations for those unique systems. There were areas separated by MFL walls that had different criteria and those were calculated separate as they were unique systems.

If I have a 6 story hotel, where floors 2-6 are identical, would I need to provide calculations for every floor, or just calculate Level 6 and size the others based on level 6 calcs? I often run calcs on a lower floor just to see if I can reduce pipe sizes, but if I can't, then I don't bother submitting that calc.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[SpcFoor]

I always run calcs on all systems in the building. If the systems are the same I will reuse the same nodes and just change the footage of bulk pipe as needed. I recently did a 150,000sqft tire distribution warehouse that three of the four systems were identical minus the bulk pipe footages. I calced the furthest system first and based my pipe sizes off of that first calc and then calced the rest of them to prove it.

 

[MGXFP]

Logically if a warehouse has 8 typical systems and the design criteria for the fire suppression is identical throughout, if pipe sizes and fire sprinklers are the same, it makes little sense to need to calculate each system.

Personally I would calculate the most remote/demanding and then see if the pipe sizes could be reduced to save money on the remainder of the systems. Otherwise it just seems to be using extra paper.

 

[chicopee]

You still need to list the hydraulic calculation on each riser. So if you have 10 risers you will need 10 placards posted at the 10 sprinkler alarn check valves.

 

[SprinklerDesigner2]

A few years ago I landed one of those once-in-a-lifetime project having 12 systems where every system was identical to each other in every respect. I ended up with 12 identical hydraulic calculation placards. Doesn't happen often.

But pipe between the source and base of riser was not typical so I ended up with 24 sets of calculations enough to fill a phone book. They all came out close but non were identical.

Gridded ESFR side fed systems so why did I end up with two sets of calculations per system?

Building was 200'x200' with 24' eave and 1 in 12 pitch to the peak at center of the center of the building. Sprinklers adjacent to peak were 7'-6" higher than sprinklers along the eave and that made a difference by a good couple of pounds putting my hydraulically most demanding area not at the far end of the system where most would think it would be but halfway back toward the riser smack in the middle of the system. So I submitted two sets; one showing the most remote where some might expect it to be the other showing where it actually was knowing if I didn't show where it was expected to be there would have been questions my the local AHJ.

Gentlemen, if you got systems that straddle peaks where cross mains are rather large you really should do two sets of calcs because it might just surprise you.

 

[Sdpaddler50]

Interesting posts. My usual disclaimer, i am not a sprinkler designer, so i leave the fine details to guys like you who have posted. When i have reviewed plans for big DC's in the past, i was thinking there were slight differences to each system (if memory served me correct). But, in the big scheme of things its a non isssue. The key thing, as we all know is whether the sprinkler design is appropriate for the incoming storage, and that is where the fire protection community needs work, especially for spec blgds. IMO, specs should be designed for plastics - period. Being 19 gpm and 1.4 psi off on the hydraulic calcs is not going to result in an uncontrolled fire. Having an OH-II design protecting plastics to 20 ft high...fill in the blank.