1 / 44

Chapter 11

Chapter 11 . Nozzles, Fire Streams, and Foam. Introduction. Fires usually extinguished by water Foam added to improve water’s extinguishment ability For fires where water ineffective Water and foam delivered using nozzles and fire streams Nozzle selection important

matia
Download Presentation

Chapter 11

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 11 Nozzles, Fire Streams, and Foam

  2. Introduction • Fires usually extinguished by water • Foam added to improve water’s extinguishment ability • For fires where water ineffective • Water and foam delivered using nozzles and fire streams • Nozzle selection important • Each fire situation requires different appliance

  3. Definition of Fire Stream • Fire stream: extinguishing agent that leaves the nozzle and flows toward its target • Four elements affecting the stream: • Pump • Water • Hose • Nozzle • Proper stream has sufficient volume, pressure, and direction to reach its target

  4. Nozzles • Nozzles: appliances that allow application of extinguishing agent • Two types: solid stream and fog • Combination nozzles: straight stream or adjustable spray patterns • Nozzle pressure: pressure required for effective nozzle operation • Relates to flow and reach • Nozzle flow: amount of water a nozzle provides at a given pressure

  5. Figure 11-1 Nozzles showing the stream shape for straight, solid, and wide pattern streams.

  6. Nozzles (cont’d.) • Nozzle reach: distance the water will travel after leaving the nozzle • Nozzle reach a function of water pressure • Affected by stream shape, water pressure, wind direction, gravity, air friction • Stream shape (stream pattern): configuration of droplets of water as they leave the nozzle • Nozzle reaction: nozzle moves in opposite direction of water flow

  7. Solid Tip or Stream • Deliver unbroken stream of water • Solid stream nozzle delivers water as a solid cone of water • Large droplets when bounced off wall, ceiling • Flow a factor of tip size at a certain nozzle pressure • Minimal effect of room’s thermal balance • Disadvantages: lack of volume control, lack of fog protection, higher nozzle reaction

  8. Fog Nozzles • Deliver fixed spray pattern or variable combination pattern • Straight stream and spray patterns • Fog provides better heat absorption, but can change to steam • Excellent tools for hydraulic ventilation • Large quantities of smoke removed by aiming fog cone out an open window • Can also draw heat from the fire

  9. Figure 11-6 Variable combination fog nozzle patterns. From top to bottom: straight stream, narrow fog, and wide fog.

  10. Figure 11-7 Parts of a fog nozzle.

  11. Straight Stream • Creates a hollow type stream • Similar to solid stream pattern • Straight stream pattern must pass around the baffle of the nozzle • Creates an opening in the pattern • May allow air into the stream and reduce its reach • Newer designs have hollow effect from the tip • Short distance to refocus the stream to create solid stream with good reach and penetration

  12. Figure 11-11 Comparison of (A) straight and (B) solid streams at tip.

  13. Special Purpose • Not often used • Cellar nozzles and Bresnan distributors: • Fight localized fires in basements when firefighters cannot make direct attack • Piercing nozzles originally designed to penetrate the skin of aircraft • Modified to pierce through building walls and floors • Water curtain nozzle • Sprays water to protect against heat exposure

  14. (A) (B) Figure 11-12 (A) Cellar nozzle and (B) Bresnan distributor.

  15. Figure 11-14 Water curtain nozzle. Figure 11-13 Piercing nozzle.

  16. Nozzle Operations • Solid tip nozzles easy to operate • Nozzle size and tip selected to match desired flow • Carry smaller nozzle tips in pocket • Fog nozzles with rotating valves common for wildland firefighting • Gallonage and pattern adjustments detected in the dark because nozzle clicks at each position • Fog nozzles have more applications than smooth bore nozzles • Considered more effective

  17. Operating Hoselines • Chapter 10 covers: • Advancing hoselines, initial nozzle operation • Straightening the hose • Properly spacing firefighters on same side of line • Bleeding off air from hose and nozzle • Selecting proper pattern • Most hoselines operated from crouching or kneeling position • Lying, standing, or sitting positions also used

  18. Small-Diameter Handlines • Small-diameter handlines: • Typically 1½, 1¾, or 2 inches in diameter • Flow from 100 to over 250 gpm • When flowing at lower volumes, operated by one person • Larger volumes require two people • Fog and solid tip nozzles can be used for small lines • Small lines popular because of ease of mobility, number of personnel, extinguishing ability

  19. Medium-Diameter Handlines • Medium-diameter hose for handlines: • 2½-inch or 3-inch hose • Solid tip and fog nozzles • Flow from 165 to 325 gpm • 2½-inch hose is standard size hoseline • Many departments use 1¾-inch and 2-inch for attack • Increased maneuverability • Large commercial structures or buildings with high fire loading require increased gpm flow of 2½-inch line • Require two or more personnel to operate

  20. Master Stream Devices • Master stream devices capable of 350 gpm • Main artillery of fire service • Used when large volumes of water required • Must be apparatus-mounted or secured properly • Require only one person to operate • Lack of mobility

  21. Stream Application, Hydraulics, and Adverse Conditions • Applications of fire streams vary according to method of fire attack, conditions encountered • Including environmental factors and water supply • Fire streams must have proper pressure and flow • Firefighters must understand hydraulics • Improper hydraulic calculations are the leading cause of poor fire streams

  22. Direct, Indirect, andCombination Attack • Direct fire attack • Aim the flow of water directly at the seat of the fire • Used on deep-seated fires that require penetration • Indirect fire attack • Apply a fog stream into a closed room • Convert water into steam to extinguish the fire • Combination attack • Typical attack in structural firefighting

  23. Figure 11-20 Firefighter directly attacking a fire.

  24. Figure 11-21 Firefighter using indirect attack by applying water into room and then closing the door.

  25. Figure 11-22 One cubic foot of water in liquid form expands 1,700 times when converted to steam at 212°F.

  26. Figure 11-23 Firefighter using combination fire attack directing the stream from the ceiling to the fire with a circular, “Z” or “T” motion.

  27. Basic Hydraulics, Friction Loss, and Pressure Losses in Hoselines • Hydraulics: study of fluid in motion • Pressure: force divided over an area • Flow: rate and quantity of water delivered • Friction loss: loss in pressure due to friction • Discharge pressure of a pump: EP = NP + FL ± E + SA

  28. Figure 11-27 Example for friction loss and engine pressure calculations.

  29. Adverse Conditions • Two types: natural and man-made • Natural: • Wind and wind direction • Breaks up stream and deflects it from its target • Rain, snow, hail, tree branches, wires, etc. deflect and break up hose streams • Gravity and air friction: • Move closer to the target or to a better position

  30. Types of Foam andFoam Systems • Class B foam: specially formulated concentrated liquid foaming agents • Creates a blanket that cools and smothers the fire • Seals in vapors • Class A foam: detergent or soap-based surfactants • Penetrate ordinary combustible materials • Keeps fuel wet and reduces its ability to burn

  31. Foam Characteristics • Protein foam: natural protein materials with metallic salts • Fluoroprotein foam: improved protein foam with fluorinated surfactant added • Alcohol-resistant foam: contains a polymer • Forms a layer between burning surface and foam • Fluoroprotein film-forming foam (FFFP): • Combines protein with film-forming fluorosurfactants • Detergent-type foams: synthetic surfactants break surface tension of water

  32. Classification of Fuels • Foams used for Class A and B fires • Specific considerations affect their use

  33. Class A • Piles of Class A materials extinguished using a wetting agent • Foamy water solution has the ability to cling to sides of objects • Used to protect homes in urban interface areas during wildland fires • Disadvantages: • Cost of equipment and agent, environmental effects • Fire investigation lab tests, difficult salvage operations

  34. Class B • Class B fuels: hydrocarbons and polar solvents • Firefighters do not use foam • Hydrocarbons: • Examples: heating oil, gasoline, paraffin, asphalt • Not miscible; foam is best method to extinguish • Polar solvents: • Examples: alcohols, lacquer thinners, acetone • Normal foams break down when used on fires involving these mixtures • Special foams create a polymeric barrier

  35. Figure 11-29 (A) AFFF applied on Class B fuel. Note the film barrier on the surface.

  36. Figure 11-31 Polar solvent or alcohol-type foam applied on Class B polar solvent fuel. Note the polymeric film barrier on the surface.

  37. Application of Foam • Requires a device to proportion, meter, or mix foam concentrate into the water • Air added to foam solution • Eductor: common proportioner • Works on Venturi principle • Must have proper gpm flow, correct pressure, be clean, not have back-pressure situations • Compressed air foam systems (CAFS): • Concentrate in separate foam tank • Concentrate metered by microprocessor

  38. Figure 11-33 Foam eductor using the venturi principle.

  39. Bank-In Technique Figure 11-40 The bank-in technique of foam application.

  40. Bank-Back Technique Figure 11-41 The bank-back technique of foam application.

  41. Raindown Technique Figure 11-42 The raindown technique of foam application.

  42. Fog Nozzles versus Foam Nozzles • Some nozzles combined all foam-making steps • Modern foam nozzles aspirate air and apply foam to the fuel • Air vents built into the nozzle • Designed for low and medium expansion • Recommended with protein and fluoroprotein foams • Fog nozzles can be used with foam • Clip-on foam nozzle adapters attach to the fog nozzle • Three techniques: bank-in, bounce-off, raindown

  43. Nozzle and FoamEquipment Maintenance • Nozzles and foam appliances must be cleaned and maintained regularly • Follow manufacturer guidelines and department policies • Guidelines and policies should include: • Cleaning and maintenance schedule • Necessary skill level of firefighter • Documentation procedures • Replacement and repair process

  44. Lessons Learned • Fire streams: water that leaves a nozzle and heads toward the target • Solid tip and fog nozzles • Nozzle should match fire conditions and department resources • Correct hydraulics calculations require understanding pressure and friction loss • When fuels not compatible with water, other agents are used • Foam requires special equipment

More Related