Plastic Warehouse ESFR K25.2 (K360): NFPA 13 Group A Plastics Protection

Plastic raw material — polyethylene, polypropylene and polystyrene pellets — is one of the toughest fire loads. Its heat release rate is very high, so conventional density/area sprinklers fall short once it ignites. Polymer producers' warehouses therefore use ESFR K25.2 (K360) sprinklers. Three inputs drive the design: packaging (exposed or cartoned), ceiling/storage height and the matching minimum operating pressure; the design area is always 12 sprinklers.

Plastic Group Classification

• Group A plastic (NFPA 13 20.4.5): PE, PP, PS, ABS, PET, polycarbonate, nitrile rubber, polybutadiene
• Group B plastic (20.4.6): chloroprene rubber, silicone rubber, some fluoroplastics (ECTFE, ETFE, FEP)
• Group C plastic (20.4.7): PVC with up to 20 percent plasticizer, PTFE, melamine, phenolic
• Nonexpanded vs expanded: expanded Group A (foam, EPS) is the worst case — very rapid flame spread
• Exposed vs cartoned: separate rows in Table 23.3.1; free-flowing pellets that are bagged, boxed or crated are protected as Class IV per NFPA 13 sections 20.4.4 and 20.4.8.1 (Annex Table A.20.3)

ESFR K25.2 (K360) System

• K-factor: K25.2 (K360)
• Minimum operating pressure (Table 23.3.1, pendent): exposed nonexpanded Group A — 60 psi (4.1 bar) for 35-40 ft (10.7-12.2 m) ceilings, 35 psi (2.4 bar) up to 30 ft (9.1 m); cartoned nonexpanded Group A — 40 psi (2.8 bar) at 45 ft (13.7 m) ceiling / 40 ft (12.2 m) storage
• Flow per sprinkler: at 60 psi, Q = 25.2 × √60 ≈ 195 gpm (metric: 360 × √4.1 ≈ 729 L/min)
• Design area: 12 most demanding sprinklers, four on each of three branch lines (23.2.2)
• Total sprinkler flow: 12 × 729 ≈ 8,750 L/min
• Hose allowance: 250 gpm (950 L/min), 60 min duration (Table 20.15.2.6, ESFR up to 12 sprinklers)

Pile and Rack Design

• Exposed nonexpanded Group A: K25.2 (K360) up to 40 ft (12.2 m) ceiling / 35 ft (10.7 m) storage; at 45 ft / 40 ft Table 23.3.1 gives no ceiling-only option (in-rack sprinklers required with K14/K16.8)
• Cartoned nonexpanded Group A: up to 45 ft (13.7 m) ceiling / 40 ft (12.2 m) storage
• Arrangement: solid pile, palletized or rack
• Flue spaces: 6 in. (150 mm) transverse in double-row racks (20.6.2.2); 6 in. (150 mm) longitudinal above 25 ft (7.6 m) storage (20.6.2.1.2)
• Aisles: Table 23.3.1 sets no minimum aisle width; the 8 ft (2.4 m) aisle applies only to the vertical-barrier rack arrangement of 23.4

Alternative Protection

• In-rack sprinkler: K14 (K200) level sprinklers
• CMSA K16.8 (K240): lower pressure, legacy
• High-expansion foam: special design required
• Cartoned storage: Class IV commodity
• Open shelving: ESFR may suffice

Required Infrastructure

• Pump: 12,000 L/min @ 9 bar
• Tank: demand ≈ 9,700 L/min × 60 min ≈ 582 m3; sized on pump rated flow, 12,000 × 60 = 720 m3
• Riser: DN200-250
• Zone valve: split into 4 zones
• Detection: sprinkler + smoke vent

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