Fire Detection and Suppression

1. Fire Detection and Suppression Chapter 7 Special Extinguishing Systems

2. 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

3. 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

4. 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

5. 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

6. 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. 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

8. 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

9. 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

10. Dry Chemical Systems • Common uses • NFPA 17, Standard for Dry Chemical Extinguishing Systems • Residue Special Extinguishing Systems

11. Gaseous Systems • Used where wet or dry systems may not be suitable • Extinguishing agents • Carbon dioxide (CO2) • Halogenated agents • Halon substitutes (Continued) Special Extinguishing Systems

12. 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

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

14. 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

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

16. 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

17. Foam Systems (cont.) • Foam generation • Key terms • Foam concentrate • Foam proportioner • Foam solution • Foam • Two-stage process • Proportioning • Aeration (Continued) Special Extinguishing Systems

18. 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

19. 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

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