Essentials Of Fire Fighting Seventh Edition Chapter 18

Essentials Of Fire Fighting Seventh Edition Chapter 18 Foam Fire Fighting, Liquid Fires, and Gas Fires

Learning Objectives 1 -2 Describe methods used to generate fire fighting foam. Identify materials and equipment needed to generate fire fighting foam. 18– 1

Foam Fire Fighting Separating Creates barrier between fuel gases and ignition sources Cooling Lowers temperature of fuel and adjacent surfaces Smothering Prevents air from reaching the fuel and mixing with vapors and prevents release of flammable vapors Penetrating Lowers surface tension of water and allows it to penetrate fires in Class A materials (Cont. ) 18– 2

Foam Fire Fighting (Cont. ) 18– 3

Foam Fire Fighting Class B foam Class A foam 18– 4

Class A And B Foams Class A foam Class B foam • Intended for use on ordinary combustibles • Solid fuels — Foam blankets and cools the fuel and stops the burning process • Lowers the surface tension of water so it can penetrate deeper to extinguish the fire • Water is released as the foam collapses, which produces a cooling effect • Intended for use on flammable liquids • Foam blanket prevents or reduces release of flammable vapors • Especially effective on hydrocarbon fuels and polar solvents 18– 5

REVIEW QUESTION List ways that fire fighting foam extinguishes fires and/or prevents ignition. 18– 6

Foam Generation — Proportioning 18– 7

Foam Generation — Aeration 18– 8

Foam Expansion Degree of expansion depends on Type of foam concentrate Accurate proportioning (mixing) of foam concentrate in the solution Quality of foam concentrate (shelf-life or storage conditions) Method of aeration and sizing of bubbles (Cont. ) 18– 9

Foam Expansion 18– 10

CAUTION Failing to match the foam type and concentrate to the burning fuel will result in an unsuccessful extinguishing attempt and could endanger firefighters. Likewise, mixing different types of foam can result in substandard quality foam and can foul pumps and other equipment. 18– 11

Foam Concentrates — Nozzles Used Fog nozzles Air-aspirating foam nozzles Medium- and highexpansion devices Apparatus-mounted systems 18– 12

Class A Foam Designed for use on Class A fuels; used in wildland structural fire fighting Surfactants reduce surface tension of water in the foam solution, allowing better water penetration in the fuel and increasing effectiveness Coats and insulates fuels, preventing pyrolysis and ignition 18– 13

Class B Foam Prevents ignition, extinguishes, and suppresses vapors from fires involving flammable and combustible liquids Hydrocarbon fuels Polar solvents (Cont. ) 18– 14

Class B Foam Rate of application depends on Type of foam concentrate used Whether the fuel is on fire Type of fuel Whether the fuel is spilled or contained in a tank Whether foam is applied via fixed system or portable equipment (Cont. ) 18– 15

NOTE If the fuel is in a tank, the type of tank will have a bearing on the application rate. 18– 16

Class B Foam blanket suppresses vapors from unignited spills Courtesy of James Mack/ Richmond International Airport (Cont. ) 18– 17

Class B Foam concentrate supplies should be at the point of proportioning before application begins • Once application starts, it should continue uninterrupted until extinguishment is complete • Stopping and restarting may allow the fire to consume the foam blanket 18– 18

Application Rates • Polar solvents have differing affinities for water • Rates vary with type and manufacturer of the concentrate • Information sources – Underwriters’ Laboratories (UL) – NFPA 11 – Manufacturers’ recommendations 18– 19

REVIEW QUESTION What must happen in order to produce high quality foam? 18– 20

Foam Hazards Mild irritant to skin and eyes May be harmful if inhaled or ingested Can degrade PPE Most are mildly corrosive Environmental concerns 18– 21

REVIEW QUESTION What hazards can fire fighting foam pose to firefighters and the environment? 18– 22

Foam Proportioning Water Foam solutio n Foam concentra te (Cont. ) 18– 23

Foam Proportioning 3% mixture 6% mixture (Cont. ) 18– 24

Foam Proportioning Selection of a proportioner depends on • Foam solution flow requirements • Available or correct water pressure • Intended use for the foam • Foam agent Using a proportioner that is not compatible with the delivery device can result in unsatisfactory foam or no foam 18– 25

Foam Proportioning — Eduction 18– 26

Foam Proportioning — Injection 18– 27

Foam Proportioning — Premixing • • • Limited to one time application Tank must be emptied and refilled before it can be used again Most Class A foam solutions are biodegradable — Mixing and storing the solution for a long period of time can result in decreased foaming ability 18– 28

REVIEW QUESTION What are three methods of foam proportioning? 18– 29

Foam Proportioners Equipment needed to produce a foam stream Pump Foam proportion er Fire hose 18– 30 Delivery device (nozzle or generating system)

In-line Foam Eductors Follow manufacturer’s instructions about inlet pressure and maximum hose lay between eductor and discharge nozzle Pickup tube is connected to the eductor at a low point Pickup tube draws foam concentrate into the water stream 18– 31

Foam Nozzle Eductors Eductor is built into the nozzle rather than the hoseline Foam concentrate must be available at the nozzle Relocating foam containers can be a problem Supplies may have to be left behind if firefighters are required to retreat 18– 32

Apparatus-Mounted Proportioners Around-the In-line -pump eductors proportione rs Balancedpressure proportione rs 18– 33

Compressed Air Foam Systems (CAFS) Mounted on many types of apparatus Centrifugal pump supplies the water Direct-injection proportioning system mixes foam solution with water on the discharge side of the pump Onboard compressor adds air before discharge 18– 34

DISCUSSION QUESTION What types of foam proportioners are commonly used in your jurisdiction? 18– 35

Fog Nozzles Vs. Foam Nozzles Foam nozzle s Fog nozzle s 18– 36

Fog Nozzles Produce low-expansion, shortlasting foam Break foam solution into tiny droplets Use agitation of water droplets moving through the air to achieve foaming action Some nozzle manufacturers have foam aeration attachments to increase aeration (Cont. ) 18– 37

Fog Nozzles Advantages • Widely available • May allow for variable flow and pattern of application • Adjustable gallonage of water • Faster application when using preconnected hoseline • May allow a margin of safety if foam supply is lost • Greater reach than foam nozzles (Cont. ) 18– 38

Fog Nozzles Disadvantages • Operator error is more likely to produce less than optimum foam proportion • Additional equipment and setup time • May not create same quality of foam as specialized equipment • May create appearance of better flow than is actually being produced • Needs maintenance more frequently if consistently used for foam • Necessary to match flow of water with all equipment • Generally do not provide optimal foam expansion; do not make the best use of the foam supply 18– 39

Foam Nozzles Most effective appliance for generating low, medium, or high -expansion foam Inducts air using Venturi Effect Designed to provide aeration required to make highest quality foam Provide best expansion Less stream reach than a fog nozzle (Cont. ) 18– 40

Foam Nozzles Advantages • Typically produces higher quality foam than fog nozzles • Useful in blanketing operations Disadvantages • Not as versatile as fog nozzles • Limited reach compared to other nozzles 18– 41

REVIEW QUESTION What advantages do foam nozzles have over fog nozzles? 18– 42

Assembling A Foam Fire Stream System Common reasons for failure to generate foam or for generating poor-quality foam • Eductor and nozzle flow ratings do not match, preventing foam concentrate from inducting into the stream • Air leaks at the proportioning device • Improper cleaning of proportioning equipment • Nozzle is not fully open • Hose lay on the discharge side is too long • Hose is kinked • Nozzle is too far above the eductor • Mixing different types of concentrates in the same tank • Improper pump pressure 18– 43

DISCUSSION QUESTION If you notice that the foam you are producing is poor quality, what items should you check in order to fix the problem? 18– 44

Learning Objective 3 Describe methods of foam application. 18– 45

Foam Application Techniques • • • Directs foam stream on the ground near the front edge of the spill Foam rolls across the fuel surface Continue to apply foam until it spreads across entire surface and fire is extinguished May need to move stream to different positions to cover the entire pool Used only on pool of liquid fuel on the open ground (Cont. ) 18– 46

Foam Application Techniques • • May be employed when elevated object is near or within the area of the liquid Foam is directed onto the object, and runs down onto the surface of the fuel May be necessary to direct the stream around various points to achieve total coverage and extinguishment Used primarily on fires in diked pools and storage tanks and for fires involving spills around damaged or overturned transport vehicles 18– 47 (Cont. )

Foam Application Techniques • • • Used when other two methods are not feasible Primary manual method used on aboveground storage tank fires Directs stream above the fire or spill and allows foam to float onto the fuel surface Stream can be swept back and forth until the surface of the fuel is entirely covered and fire is extinguished May be more effective to direct the stream at one location, allow the foam to collect, and then float out from that point 18– 48

DISCUSSION QUESTION Provide an example scenario for when each method of foam application would be used: roll-on, bank-down, and rain-down. 18– 49

Retreating To A Safe Location • Remain alert to changing conditions • If fire begins to spread uncontrollably, retreat • • to a safe location Use foam handlines to protect the evacuation route Water handlines can be used for protection, but water may displace foam applied during attack Safe locations should be uphill and upwind Vehicles should not be driven through unignited or burning fuels 18– 50

REVIEW QUESTION What actions should firefighters take to protect themselves when retreating to a safe location? 18– 51

Learning Objective 4 Describe operations involving liquid and gas fuels. 18– 52

Liquid And Gas Fuel Fires Combustible liquids Flammable liquids • Flash points of less than 100°F (38°C) • Can be ignited without being preheated • Flash points higher than 100°F (38°C) • Must be heated above their flashpoint before they can be ignited (Cont. ) 18– 53

Liquid And Gas Fuel Fires Hydrocarbo ns Polar solvents Do not mix with water Mix with water (Cont. ) 18– 54

Liquid And Gas Fuel Fires Foam Most often used to control flammable liquid fires Cooling agent Water Mechanical tool Crew protection (Cont. ) 18– 55

Liquid And Gas Fuel Fires (Cont. ) 18– 56

Liquid And Gas Fuel Fires Determine wind direction Locate apparatus uphill and upwind Establish perimeter Report conditions to all responding units and the communications center Evacuate civilians in the affected area Request a hazardous materials company and remain outside the hot zone Establish a water supply and deploy attack hoselines as required (Cont. ) 18– 57

Liquid And Gas Fuel Fires Avoid standing in pools of fuel or contaminated runoff • Protective clothing can absorb fuel, which can lead to skin irritation and clothing catching on fire • Pool could ignite • Benzene in petroleum product fumes is a known carcinogen Remove soaked PPE from service until it is cleaned 18– 58

WARNING PPE soiled with flammable and combustible liquids may ignite when exposed to heat. 18– 59

REVIEW QUESTION What is the difference between a flammable liquid and a combustible liquid? 18– 60

Pressurized Vessels Courtesy of Rich Mahaney 18– 61

Propane Liquid petroleum gas (LPG) Stored in pressurized tanks and transported by railcars and tanker trucks Odorless gas that is heavier than air Ethyl mercaptan added to give it a distinct smell (Cont. ) 18– 62

Propane Flammable Can be explosive under the right conditions Response to a leak should include notification of the propane company Heated tanks can explode and send shrapnel great distances 18– 63

Industrial Pressure Vessels • Commonly hold many different products • • in industrial operations Utility boiler units produce steam and heat Operate above 15 pounds per square inch gauge (psig) (approximately 200 k. Pa) Do not attempt to isolate operations of the pressure vessel without training Obtain assistance from facility maintenance 18– 64

DISCUSSION QUESTION Are there any locations in your jurisdiction where you are likely to encounter propane (LPG) tanks? 18– 65

Valve Control Know exactly what valve or shutoff is being closed and what system it will affect Must be coordinated with facility personnel supervision (Cont. ) 18– 66

Valve Control Valve operation 18– 67

Boiling Liquid Expanding Vapor Explosions (BLEVEs) Pressure vessel containing liquid or liquefied gas is heated Liquid expands Liquid reaches boiling point and returns to gaseous state Vessel’s internal pressure increases Vessel loses structural integrity and ruptures Pressure and contents of the vessel are released (Cont. ) 18– 68

Boiling Liquid Expanding Vapor Explosions (BLEVEs) • Liquid or liquefied gas must be above its • • boiling point at standard temperature and pressure Produces an explosion Tank failure may occur because of mechanical damage or direct flame impingement Many types of container breaches PRD allows gases to exit the cylinder (Cont. ) 18– 69

Boiling Liquid Expanding Vapor Explosions (BLEVEs) Safety measures when fighting fire involving pressurized, liquid fuel tanks • Fight fire from maximum distance possible • Apply water to upper portions of the tank, preferably from unattended master stream devices (Cont. ) 18– 70

Boiling Liquid Expanding Vapor Explosions (BLEVEs) Safety measures when fighting fire involving pressurized, liquid fuel tanks • Flood outside of containers with large quantities of water until after fire is out • Direct water away from leak sources or safety devices • Leave area immediately if you hear a rising sound from venting safety devices or see discoloration of the tank • Sections of tank can fly in any direction — Just avoiding the ends of the tank is not enough 18– 71

Precautions And Safety Measures When Fighting Fires Involving Pressurized, Liquid Fuel Tanks 18– 72

REVIEW QUESTION What can cause a BLEVE? 18– 73

Bulk Transport Fires Extinguishment techniques are similar to fires in flammable fuel storage facilities • Amount of fuel available • Possibility of vessel failure • Danger to exposures Always follow preincident plans (Cont. ) 18– 74

Bulk Transport Fires Additional challenges at fires involving vehicles transporting flammable fuels and fires involving flammable • Increased life safety risk to firefighters from traffic fuel storage facilities • • • Increased life safety risks to passing motorists Reduced water supply Difficulty identifying products involved Difficulty containing spills and runoff Force of collisions weakening or damaging tanks and piping • Instability of vehicles • Additional concerns for civilians and civilian structures because of relocation of the incident (Cont. ) 18– 75

Bulk Transport Fires Traffi c • Many incidents handled while traffic passes at normal speeds • At least one lane of traffic and the incident lane should be closed during initial operations • Avoid using road flares • Trained firefighters should be assigned to direct traffic and control access if law enforcement personnel are unavailable • Follow proper highway procedures (Cont. ) 18– 76

Bulk Transport Fires Additional consideratio ns • Tires could fail, which causes the flammable load to shift • Status and limitations of the water supply vary more than at fixed facilities • May be necessary to protect trapped victims with hose streams until they can be rescued (Cont. ) 18– 77

Bulk Transport Fires Determining the nature of cargo • Bills of lading, manifests, placards, or drivers • If these can’t be found, contact shippers or manufacturers Environment al protection • Prevent runoff of contaminated water and spilled liquids by blocking storm drains 18– 78

REVIEW QUESTION What hazards are firefighters likely to encounter at incidents involving bulk transport of flammable fuels? 18– 79

Gas Cylinder Fires Fog-stream patterns can be used as crew protection when advancing to shut off valves When pressure vessels containing gases are exposed to flame impingement, apply solid streams from their maximum reach until relief valves close No angle or direction of approach is safer than any other angle 18– 80

REVIEW QUESTION What safety precautions should be in place when approaching a gas cylinder fire? 18– 81

Fires In Gas Distribution Systems Vast network of surface and sub-surface pipes Pressures range from 1, 000 psi (7 000 k. Pa) in the distribution network to 0. 25 psi (2 k. Pa) at the point of use Excavation equipment breaking through pipes is generally the cause of most incidents • • Call utility company immediately Apparatus should approach from and stage on upwind side Wear full PPE Be prepared for explosion and fire (Cont. ) 18– 82

Fires In Gas Distribution Systems • • Evacuate area immediately around the break and downwind Eliminate ignition sources Check surrounding buildings for gas odor Follow SOPs regarding crimping a gas line to stop a leak If gas is burning, flame should not be extinguished Use hose streams to protect exposures if necessary Contact utility company and an attempt to shut off pressurized gas supply should be made Request hazardous materials team if available 18– 83

WARNING If gas is burning from a broken gas pipe, do not extinguish the fire. Provide protection for exposures. 18– 84

REVIEW QUESTION What steps must be taken in the event of a CNG or LNG pipe rupture? 18– 85

Preventing Reignition Occasionally reapply fresh foam to ensure adequate coverage of the foam blanket Do not walk, drive into, or strike foam blanket with solid or straight stream 18– 86

Retreating To A Safe Location Sound of gas escaping the relief valve may indicate that rupture is imminent Foam handlines may be used for protection Water can be used, but streams may displace foam Safe locations should be uphill and upwind Vehicles should not be driven through unignited or burning fuels 18– 87

REVIEW QUESTION What clue signals the need to retreat to a safe location rather than continuing to fight a liquid or gas fuel fire? 18– 88

QUESTIONS Are there any questions about this content? 18– 89