Hydraulic Calculations Required for Each Zone?

7/24/2020

I need an answer for a simple question. I am working on a large airport project expansion. I have a structure of 4 levels with 70+ sprinkler zones.

Is there an NFPA standard requirement stating that each area requires a hydraulic calculation on each system?

Each system is not prototypical.

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11 Comments

Glenn Berger

7/24/2020 10:13:14 am

Since each system is not identical, separate calculations would be required.

Are you trying to size piping identically? Are the spaces the same hazard categories?

Jessica L.

7/24/2020 10:42:00 am

An experienced sprinkler plan reviewer should be ok with you submitting one calc per hazard/sprinkler k-factor/system type/pipe size arrangement. ****Be sure you have the knowledge and experienced to make this judgement, and defend it!

Also, check with the airports' submittal requirements...some airports are managed by various parties, with unique requirements specific to each airport...they could possibly required a calc for each zone, or have other special requirements that go beyond NFPA 13.

Ivonn

7/24/2020 11:06:19 am

I dont have a simple answer maybe no, are there 70 zones or 70 systems?, all zones have the same hazard? What are the most critical pipe configuration?, What is the critical path? What is the most remote or high vs the supply? You need to consider that questions and make a decision

For example in the 4th floor have 3 zones but the farest from supply its a light hazard and the nearest its an extra hazard, the two in a tree pipe configuration, personaly I will calculate the extra hazard or if the farest part is a grid system and the nearest is a tree, tree its more "critical" but I want to choose the lower diameter possible so I will calculated both.

If you have multiple ocupancies (LH,OH,EH) and multiple pipe configurations (Grid, tree, loop), maybe you need to do several hydraulic calculations, but maybe no 70+

Also you need to consider what the AHJ required, NFPA 13 Ed. 2019 do not required one hydraulic calculation per "zone" or per "level" as far as I know.

CJ Bonczyk

7/24/2020 11:42:42 am

If the systems are not entirely identical in layout I strongly recommend doing the calculations to indicate the hydraulic capability of each zone. For instance if a remodel happens within an area on a specific floor there is no way in determining the hydraulic capability of the system installed. Occupancy changes, building remodels or MIC issues, can alter system capability within a year or two. If something happens from a legal standpoint you have documentation to fall back on on how the system area was protected and why. These placards are usually required on each by the fire marshal anyway. NFPA 13 2019 Handbook Section 28.5 gives a clearer reason why these should be placed on each system.

The only time in which I have used the same hydraulic placard for corresponding floors is if I had an exact layout for multiple floors and I calculated the highest floor and used the same hydraulic plate for the lower floors and denoted on the lower floor placards that the information was based on the hydraulic capability/demand of the highest floor.

Also as Jessica stated earlier confirm with the airport that there is no insurance carrier that will require calculations for all systems.

Jesse

7/24/2020 12:43:40 pm

If by zone you mean system, then yep, each system needs to be proven. Its most acceptable proving the end-head back to the residual hydrant as opposed just to base of riser so even if each system were identical, the distance from BOR to residual hydrant would be different. If its a single system with multiple zones, the most hydraulically remote would be all that's needed but be prepared to defend your logic. And totally agree with a previous comment about proving multiple areas in case of a future remodel. I rarely sign a drawing with only one area calc'd unless it's very small for that very reason.

Franck

7/24/2020 03:20:22 pm

Working for an insurance company, I can confirm what has been said.
As a minimum, one hydraulic calculation per different system (as all results might be slightly different, and we are looking for « actual design ».
In addition, if different hazards/configuration on one system, we may ask several calculations to be sure that all configurations are adequately covered.
This is particularly true for EH occupancies or for different storage commodities/arrangement

Jimmy Landmesser, Jr.

7/24/2020 04:44:17 pm

So, first what you mean by "zone" would need to be understood.
As stated above, there are two main reasons that a single building requires multiple design calculations- 1) multiple systems serving said building or 2) when you there are different design bases (also called occupancy hazards) present. As others have said, only a single design calculation is required for the most remote area of a single system or design basis, even if multiple floors are fed from a single system. Each floor will normally have a zone control valve. On the other, there are sometimes different "zones" on a single floor that each have a different design basis. For example, a building that has offices that are light hazard, an automotive garage of ordinary hazard and high rack storage that is an extra hazard occupancy. Though a single system of a one-story building, each of these areas will require an independent design calculation.

As for reference, per NFPA 13 (2019)- 19.2.3, "the total system supply requirements for each design basis shall be determined in accordance with the procedures of Section 27.2 unless modified by a section of Chapter 19 or Chapter 20.".

Max

7/24/2020 05:07:39 pm

I would ask for one remote area calculation per riser at a minimum.

Mike

7/24/2020 07:52:03 pm

Considering the simplicity of today's CAD systems, it's relatively easy to calc many areas in a short amount of time. I'd do a detailed analysis of your different systems. If you use area reduction in some areas but not others, I wouldn't expect those designs to be used in areas where area reduction isn't a factor.

7/25/2020 03:47:24 am

The basic of all calculations are there to demonstrate your decision against Code/AHJ and justify your design, in this case is NFPA 13. There is no hard and fast rule for this. This is just subjective. So i would suggest performs as much as cals to covers as below;

-Demonstrate you get water with adequate pressure at FARTHEST location
-LARGEST DEMAND Area (Consider Occupancies w.r.t. levels/zones)
-WORST Case, which will decide your system sizes at the end.

So based on my limited knowledge about Airport structure, probably 12-15 calculation for difference Occupancies/Area should serve the purpose but certainly not 70+....

koray uluc link

7/26/2020 05:18:54 am

According to NFPA 13 if you design systems with hydraulic calculation method then you should run a calculation for all of them according to NFPA13 27.2.4.1
Sometimes AHJ may ask (in my point of view, should ask) for additional calculations to be sure that designer did choose actual "most demanding area"(NFPA13 A.27.2.4.7).
Don't forget that sloped ceilings and grid type piping makes hard to find the most demanding area at first attempt.

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