ESFR On Line Spacing Less Then 8' Options??

[LCREP]

I have a client with ESFR system obstructions and I am looking for options.

Here is what I have, the heads are K17 pendent with 23 lines running East to West. One head on each line is obstructed in the same location by being too close to bar joist. If we move the head so it is 12" from the obstruction it will be 7'6" away from the adjacent sprinkler, less then the 8' required by NFPA and FM 2-2. I can not use an upright K 17 because I have exposed non-expanded plastics.

Only option I can think of is to install a baffle on the 23 heads to prevent the water from one ESFR hitting the other. Any idea how large this baffle should be? I am thinking 2' wide by 2' deep with the ESFR head centered. The heads are 10-14" below the desk.

Suggestions comments?

 

[stookeyfpe]

I don't like baffles because they themselves are an obstruction. I would model the sprinkler performance and the impact of the spacing using FDS.

Seek professional engineering assistance.

 

[LCREP]

FYI
I called FM and spoke to the guy who wrote FM Data Sheet 2-2. He said since the ceiling was only 30' based on testing it was OK to place the heads at 7'6". Skipping and wetting of the adjacent sprinkler would not be a problem.