Немножко мудрости от FM Global:
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2.1.1.4.1 Ceiling-Level Sprinklers Above Open GridsDesign ceiling-level sprinklers as recommended in the relevant occupancy-specific data sheet. If the occupancy-specific data sheet does not address open grids, design the system as though no open grid was present.
2.1.1.4.2 Sprinklers Under Open GridsUnless recommended otherwise in a relevant occupancy-specific data sheet or in Section 2.1.1.4.3 of this data sheet, install sprinkler protection under open grids using 160°F (70°C) nominally rated quick-response sprinklers having the same:
• K-factor,
• orientation, and
• area spacing
as the sprinklers installed at ceiling level.
Install Nonstorage sprinklers under open grids on a maximum linear spacing of 13 ft (3.9 m) and a maximum
area spacing of 130 ft2 (12 m2), using the same branchline piping installed at ceiling level.
Sprinklers installed under open grids as outlined above do not need to be added to the hydraulic design of the ceiling-level sprinkler system.
2.1.1.4.3 Exceptions for Sprinklers Under Open GridsSprinklers are not required under an open grid when the following conditions are met:
Exception 1:
• The open grid is a minimum of 70% open, and
• The open grid is a maximum of 1⁄2 in. (13 mm) deep, and
• The open grid is at least 3 ft (0.9 m) vertically below the deflector of the ceiling-level sprinklers, and
• Materials that could obstruct sprinkler discharge are not present on top of the open grid, and
• The required minimum flow rate from each individual sprinkler, when divided by the area spacing of the sprinklers, is equal to or less than 0.10 gpm/ft2 (4 mm/min).
Exception 2:
• The open grid is a minimum of 70% open, and
• The open grid is a maximum of 1⁄4 in. (6 mm) deep, and
• The open grid is at least 3 ft (0.9 m) vertically below the deflector of the ceiling-level sprinklers, and
• Materials that could obstruct sprinkler discharge are not present on top of the open grid, and
• The required minimum flow rate from each individual sprinkler, when divided by the area spacing of the sprinklers, is equal to or less than 0.20 gpm/ft2 (8 mm/min).
Exception 3:
• The open grid is a minimum of 70% open, and
• The open grid is a maximum of 1⁄4 in. (6 mm) deep, and
• The open grid is at least 3 ft (0.9 m) vertically below the deflector of the ceiling-level sprinklers, and
• It is not possible for materials to fall onto the top of the open grid and obstruct sprinkler discharge during a fire, and
• There is only one open grid ceiling between the solid ceiling and the floor, and
• The ceiling sprinkler system can protect the occupancy in the absence of the open grid.
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И пара файлов с выдержками из NFPA, которые "Огнеборец" к TYCO'вским оросителям прикладывает (у FM, всё-таки, требования пожёстче).