I am in agreement of DM2. You cannot provide water spray on the roof of the floating roof as it was never a safe practice to provide. However on the tank shell (sides) you can. That is . . . if you principle of protection is water cooling your minimum application rate shall be 0.1 gpm/sq ft. and if your principle of protection of protection is exposure protection your minimum application rate shall be 0.25 gpm /sq. ft.

Protection of the floating roof annular ring shall be then by low expansion foam with the use of foam pourers/ foam chambers or foam makers.