Fire Detection and Suppression Chapter 7 Special Extinguishing Systems

7-1 Characteristics of Special Extinguishing Systems Used where automatic sprinklers may not be the best solution to fire problems Have a limited amount of extinguishing agent Must extinguish fire to be successful

Special Extinguishing Systems 7-2 Wet Chemical Systems Used for commercial cooking hoods, plenums, ducts, and associated cooking appliances Agent typically solution of water and either potassium carbonate or potassium acetate NFPA 17A, Standard for Wet Chemical Extinguishing Systems (Continued)

Special Extinguishing Systems 7-3 Wet Chemical Systems (cont.) Engineered/pre-engineered systems Components —Storage tank for expellant gas and agent —Piping to carry the gas and agent —Nozzles to disperse the agent —Actuating mechanism (Continued)

Special Extinguishing Systems 7-4 Wet Chemical Systems (cont.) General inspection points —Mechanical damage —Aim of nozzles —Change in hazard —Proper pressures on stored-pressure containers —Check maintenance tag for scheduled service (Continued)

Special Extinguishing Systems 7-5 Wet Chemical Systems (cont.) Monthly inspection (to be performed only by trained personnel) —Check that all parts of system are in their proper location and connected. —Inspect manual actuators for obstructions. —Inspect tamper indicators and seals to ensure that they are intact. —Check maintenance tag or certificate for proper placement and information. (Continued)

Special Extinguishing Systems 7-6 Wet Chemical Systems Monthly inspection (cont.) —Examine system for any obvious damage. —Check pressure gauges. —Check nozzle blowoff caps, if provided, for damage. —Check that protected equipment or hazard has not been modified, replaced, or relocated. (Continued)

Special Extinguishing Systems 7-7 Wet Chemical Systems (cont.) Semiannual inspection (to be performed only by trained personnel) —Ensure that the size or nature of the hazard being protected has not changed. —Examine all components thoroughly. —Check liquid levels of nonpressurized containers. —Verify that the piping is not obstructed. (Continued)

Special Extinguishing Systems 7-8 Wet Chemical Systems Semiannual inspection (cont.) —Examine the system for evidence of corrosion, structural damage, or repairs. —Test all working components in accordance with the manufacturer’s instructions. —Correct any problems noted in accordance with manufacturer’s recommendations. —Maintenance report and recommendations to be given to a responsible person.

Special Extinguishing Systems 7-9 Dry Chemical Systems Common uses NFPA 17, Standard for Dry Chemical Extinguishing Systems Residue

Special Extinguishing Systems 7-10 Gaseous Systems Used where wet or dry systems may not be suitable Extinguishing agents —Carbon dioxide (CO 2 ) —Halogenated agents —Halon substitutes (Continued)

Special Extinguishing Systems 7-11 Gaseous Systems (cont.) Carbon dioxide extinguishing systems —NFPA 12, Standard on Carbon Dioxide Extinguishing Systems —Personnel safety —System components –Actuation device –Agent storage container –Piping –Nozzles (Continued)

Special Extinguishing Systems 7-12 Gaseous Systems Carbon dioxide extinguishing systems (cont.) —High-pressure systems/low-pressure systems —Inspection and testing

Special Extinguishing Systems 7-13 Foam Systems Typically used where water alone may not be effective Components —Water supply —Foam concentrate —Piping system —Proportioning equipment —Foam makers (discharge devices) (Continued)

Special Extinguishing Systems 7-14 Foam Systems (cont.) Types —Fixed —Semifixed Type A —Semifixed Type B —High-expansion —Foam/water (Continued)

Special Extinguishing Systems 7-15 Foam Systems (cont.) How foam extinguishes fire —Smothering/suppressing: prevents air and flammable vapors from combining —Separating: intervenes between the fuel and the fire —Cooling: lowers the temperature of the fuel and adjacent surfaces —Suppressing: prevents the release of flammable vapors (Continued)

Special Extinguishing Systems 7-16 Foam Systems (cont.) Foam generation —Key terms –Foam concentrate –Foam proportioner –Foam solution –Foam —Two-stage process –Proportioning –Aeration (Continued)

Special Extinguishing Systems 7-17 Foam Systems Foam proportioners (cont.) —Line eductors —Balanced pressure proportioner —Around-the-pump proportioner —Pressure proportioning tank system —Coupled water motor-pump proportioner —Premixed foam (Continued)

Special Extinguishing Systems 7-18 Foam Systems (cont.) Foam nozzles and sprinklers —Solid bore nozzle —Low-expansion foam nozzle —Self-educting foam nozzle —Standard fixed-flow fog nozzle —Automatic nozzle —Foam/water sprinklers (Continued)

Special Extinguishing Systems 7-19 Foam Systems (cont.) Foam nozzles and sprinklers —High back-pressure foam aspirator —High-expansion foam generators Foam system inspection and testing