1. Dry and Wet Chem Systems Ch. 8, pages 148-162 Dry Chemical Systems Dry Chem. System Components Dry Chem. Sequence of Operation Applications for Dry Chem Systems Types of Dry Chem. Systems Wet Chemical Systems

2. Dry Chemical Systems either pre-engineered or designed by supplier design details are proprietary commercial cooking dry chem is different from dry powder

3. Dry Chemical Examples Commercial cooking heavy-duty vehicles –graders, buses portable units –(up to 300 lb) –flamm. Liquids combined with foam (twin agent)

4. Dry Chem. Agents Small solid particles suspended or fluidized in air more complicated than gaseous or liquid agents

5. Dry Chem. Agents 3 broad categories sodium carbonate based potassium based multipurpose

6. Sodiium Bicarbonate based NaHCO 3 baking soda Flamm. Liquids (class B) Electrical (class C) ideal for grease fires saponify (soap-like layer)

7. Potassium based Flamm. Liquids (class B) Electrical (class C) better than sodium bicarbonate except on grease fires KHCO 3, potassium bicarbonate, Purple K KCl, potassium chloride, Super K KC 2 N 2 H 3 O 3, Monnex

8. Multi-purpose Monoammonium phosphate A B or C Form molten residue Not effective on deep fat fires Not as effective as narrow purpose agent

9. Dry Chem. advantages Rapid knockdown –minimizes damage 3D surface coating –minimizes reignition sprays, leaks etc.

10. Dry Chem. disadvantages Surface coating –messy residue –expensive cleanup caking –from moisture –vibration –particles commonly coated

11. Personnel hazard Material is non-toxic particles too large to penetrate into deep lung products of combustion harmful usual precautions to prevent exposure

12. Testing of systems Testing –messy –expensive –requires clean-up most are not tested reliability issue least risk with popular pre-engineered systems

13. Extinguishing mechanism Coating smothering heat absorption block chain reaction

14. Container From 1lb to 3,000 lb small are pressurized large have separate expellant gas cylinder minimize piping runs rupture disk see fig 8-1

15. Expellant gas cylinder For large systems 100’s of lb N 2 or CO 2 to fluidize dry chem

16. Piping and nozzles Minimize runs remix at each tee withstand pressure corrosion resistant not cast iron variety of nozzles available

17. Sequence of operation See 8-4 1. Detector senses fire 2. Signal to panel 3. Panel interprets signal, if interpreted as fire 4. Alarm sounded 5. Equipment, HVAC shutdown 6. Could be manual activation

18. Sequence of operation 7. Could have remote activation 8. Signal to actuator on propellant tank 9. Valve opened 10. Propellant flows to dry chem tank 11. Powder fluidized 12. pressure builds in tank

19. Sequence of operation 13. Rupture disk bursts 14. Fluidized particles/propellant gas flow 15. Discharge from nozzle

20. Applications Commercial cooking petrochemical paint spray booths dip tanks tranformers generators conveyors

21. Types of systems Total flood local application hand hose line pre-engineered

22. Total Flood Fill enclosure paint spray booth enclosure must be sealed ventilation shut down additional dry chem for unclosable openings

23. Local Application Hazard must be isolated –drum filling stations if liquid, consider splashing if outdoors, consider wind dispersion

24. Hand lines As a supplement to fixed system minimum 30 sec capacity/line

25. Pre-engineered Commercial restaurants vehicle fueling mobile equipment packaged units highest reliability

26. Wet Chemical Water and extinguishing chemical usually potassium based chemical pre-engineered restaurant systems