ESFR Heads and Concrete beams 1

[mechanical_beaker]

Hi Eng tips, first post for me. looks like a nice community!

I'm working on a tenant fit-out of a newly finished mixed use warehouse/office building.

The warehouse has K25.2 ESFR heads already installed in it. The heads spacing initially looked fine to me but today while on-site I noticed that there is 41"x41" concrete beams that are causing the sprinklers to not be compliant with 8.12.5.1.1.

The deflectors are 14" below the slab, this leaves 23" to the underside of the beam. Using table 8.12.5.1.1 the heads should be 5'-6" from the obstruction. However, if I space them at 5'-6" the total distance between the 2 heads on each side of the beam would be 14'-5" which is more than allowable spacing.

Is it possible to put sprinklers below the beam and treat is as a "continuous obstruction below sprinklers".

Reviewing NFPA it looks like the existing installation is not compliant and cannot be brought into compliance. If this is the case I need to notify my client.

I'm also have more senior designer in my firm review but I thought I'd try here as well.

 

[cdafd]

Do you have the brand and model ??

 

[mechanical_beaker]

They are Tyco TY9226 165°F.

 

[cdafd]

https://tyco-fire.com/TD_TFP/TFP/TFP312_08_2018.pdf

 

[cdafd]

Roof Construction
Unobstructed or obstructed construc- tion, such as smooth ceiling, bar joists, beam and girder. Where the depths of the solid structural members, as in beams and stem, exceed 12 in. (302 mm), install ESFR Sprinklers in each channel formed by the structural members.
Ceiling Slope
Maximum 2 in. rise for 12 in. run (16.7%)

Minimum Clearance to Commodity
36 in. (914 mm)
NFPA
Deflector-to-Ceiling Distance
6 in. to 18 in. (152 mm to 457 mm)

 

[SprinklerDesigner2]

The question I get is how wide are the channels? If they're between 8 and 12 foot you could put one in each channel maintaining the 100 square foot spacing but that only applies corrupts under 30 feet. For ruffs exceeding 30 ft the maximum spacing is 10 feet.

 

[mechanical_beaker]

The channels are 28'-7" with 41" wide by 41" deep beams separating them.

The existing ESFR heads are installed at 10'-"6 x 9'-0" spacing, leaving the beams as obstructions.

 

[SprinklerDesigner2]

Just to be clear are you seeing something like this?

I really hope I misinterpreted what you wrote.

 

[mechanical_beaker]

Hi SprinklerDesigner,

Those are much narrower and closer together than my structural openings.

This is an existing ESFR installation, not one that I've designed.

I believe to be compliant we will be adding sprinkler heads below the beams.

 

[SprinklerDesigner2]

From your photo it doesn't look to me like the beams are 41" deep.

Maybe I am reading it wrong but you said the beam was 41" deep and with deflectors 14" below the slap you are actually 27" above the bottom of the beam but you could drop the lines down so deflectors are 18" below the beam which would then place the deflectors 23" above the bottom of the beam.

The problem as I see it is unlike standard sprinklers we can not use beams as "baffles" on ESFR systems.

As you know if we had a 48" steel beam with 6" flanges we could not put one sprinkler 4'-0" from the beam and on the other side place a head 3'-11" because we only have 7'-11" separation between sprinklers. If I am interpreting your posts correctly I am in agreement with you this system has never been compliant and can't be brought into compliance.

 

[mechanical_beaker]

Thank you for the response!

 

[mechanical_beaker]

One thing I noticed when doing all of this ESFR research is that NFPA is not nearly as detailed as FM Global Data Sheet 2.0 when it comes to handling obstructions.

FM Global has much more detail and is easier to understand what the code compliant solution would be.

Is there anything that says if I meet FM Global I meet NFPA? I suppose thats a discussion to have with my AHJ.

Oh the joys of sprinkler design!!

Thank you for the help everyone,

 

[UFT12]

You may find out that the obstruction criteria in FM are quite similar to the ones of NFPA but keep in mind that it is not as easy to get away with it as it seems. As stated somewhere else in this forum, you cannot just meet some provisions of a code because these are the result of a thorough study based on specific models and tests which may not be the same the two standards use as reference. Unless the AHJ says otherwise, ff you want to meet FM will have to do it entirely which at the end may prove not to the owner's advantage.

Also keep in mind that FM uses a different approach when defining storage sprinklers than NFPA. FM has it all under the term 'Storage Sprinklers' while NFPA clearly has different criteria for each individual sprinkler type (e.g. CMDA, CMSA, ESFR).