In-rack arrangement - Single or double row racks?

[UFT12]

Hello,

I am looking for the correct sprinkler arrangement in protecting single row racks over 7.6 m (25') height for class I through IV per NFPA 13. The two racks form an aisle of 2.7 m (8'-10"). The outside faces of the racks are free to open space from one side and 1 m (3'-3") away from a wall from the other side. The racks have a width of 2.3 m (7'-6") each with no longitudinal space in them.

According to the definition of NFPA 13, par. 3.9.3.7.7 a single rack can have a width up to 6 ft (1.8 m) to fall in this category. My understanding, therefore, is the racks I have need to be classified as double row racks and follow double row in-rack sprinkler arrangement. However there is no longitudinal flue space to place the sprinklers. So, does this mean that the sprinklers need to be placed as face sprinklers? If this is really so, the sprinklers will not be able to cover the commodity entirely as they will be more than 6 ft (1.8 m) away from the far side of the rack face. Would that be acceptable or a middle row arrangement in the rack, typical for single racks, is more appropriate/acceptable?

Thank you.

 

[stookeyfpe]

I don't have NFPA 13 with me but I believe that sprinkler placement at the transverse flue space at each column would be compliant so long as the spacing does not exceed the "maximum distance between sprinklers dimension."

 

[UFT12]

Most of the options in table 16.3.1.1 refer to a maximum horizontal distance of 10 ft and since the limit between single row & double row is 6 ft it makes me understand (which seems reasonable) that the maximum distance a in-rack sprinkler can cover is 6 ft away from its center. So this drives me to the conclusion that just one row of sprinklers in the rack can cover up to 6 ft depth and considering running alongside as face sprinklers. But I 'm asking because I 've seen designs which are protecting arrangements of double row racks formed by two single row racks, back to back, wider than 6 ft each and some tiers are protected by a single row of heads in the flue spaces as seen in figure 16.3.1.3.1.1(A)(d). Can this be compliant with 13? It looks to me that whatever tier is shown with in-racks, they should be all double lines of sprinklers.