Presentation on theme: "Chapter 11 Nozzles, Fire Streams, and Foam. Introduction Fires usually extinguished by water Foam added to improve water’s extinguishment ability –For."— Presentation transcript:
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 –Each fire situation requires different appliance 11.2
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 11.3
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 11.4
11.5 Figure 11-1 Nozzles showing the stream shape for straight, solid, and wide pattern streams.
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 11.6
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 11.7
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 11.8
11.9 Figure 11-6 Variable combination fog nozzle patterns. From top to bottom: straight stream, narrow fog, and wide fog.
11.10 Figure 11-7 Parts of a fog nozzle.
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 11.11
11.12 Figure Comparison of (A) straight and (B) solid streams at tip.
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 11.13
11.15 Figure Piercing nozzle.Figure Water curtain nozzle.
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 11.16
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 11.17
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 11.18
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 11.19
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 11.20
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 11.21
Direct, Indirect, and Combination 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 11.22
11.23 Figure Firefighter directly attacking a fire.
11.24 Figure Firefighter using indirect attack by applying water into room and then closing the door.
11.25 Figure One cubic foot of water in liquid form expands 1,700 times when converted to steam at 212°F.
11.26 Figure Firefighter using combination fire attack directing the stream from the ceiling to the fire with a circular, “Z” or “T” motion.
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 11.27
11.28 Figure Example for friction loss and engine pressure calculations.
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 11.29
Types of Foam and Foam 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 11.30
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 11.31
Classification of Fuels Foams used for Class A and B fires Specific considerations affect their use 11.32
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 11.33
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 11.34
11.35 Figure (A) AFFF applied on Class B fuel. Note the film barrier on the surface.
11.36 Figure Polar solvent or alcohol-type foam applied on Class B polar solvent fuel. Note the polymeric film barrier on the surface.
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 11.37
11.38 Figure Foam eductor using the venturi principle.
Bank-In Technique Figure The bank-in technique of foam application.
Bank-Back Technique Figure The bank-back technique of foam application.
Raindown Technique Figure The raindown technique of foam application.
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 11.42
Nozzle and Foam Equipment 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 11.43
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 11.44