Service Delivery 3

1. Service Delivery 3 Foam

2. Aim To provide students with information to enable them to control and extinguish fires using foam.

3. Learning OutcomesAt the end of the session students will be able to: • Describe the principal methods by which foam extinguishes a fire • State the types of foam concentrate in use • List the types of foam making equipment in use • Identify the considerations when using foam making equipment.

4. How foam extinguishes fire • Formation of a sealing blanket over fuel surface which prevents vapour escaping • Interception of radiant heat from the flames, preventing it from reaching the surface of the fuel and causing further evaporation • Isolation of fuel from oxygen in the air.

5. Isolation Dilution Vapours Foam blanket Interception.

6. How foam extinguishes fire • Cooling of the fuel • Dilution of the surrounding air with water vapour from evaporated foam.

7. Main properties • Stability • Expansion • Burn back resistance • Fluidity • Contamination resistance • Sealing and resealing • Knockdown and extinction.

8. Performance can be affected • Type and operation of foam making equipment • Type of foam concentrate • Type of fire and fuel involved • Tactics of foam application • Rate at which foam is applied • Quality of water • Length of pre-burn.

9. Types of foam • Alcoseal (LX) - 4 x 22.5 litre drums on appliances • FP70 (LX) - 6 X 1000 litre cubes (bulk supply on Equipment Support Units) • Expandol (HX) - for high expansion generators.

10. Differing foam expansions.

11. Low expansion foam Up to 21 metres throw.

12. High expansion foam Negligible throw.

13. Factors affecting finished foam • Concentration to water ratio • Expansion (air mixed with solution) • Size of bubbles (HX).

14. Production of finished foam.

15. Low expansion foam • Can be projected over fairly long distances • Spreads fairly quickly • Is capable of forming a stable and secure foam blanket. This is the most widely used foam because;

16. Method of application To avoid ‘stirring’ the fuel, foam should be; • Applied gently to the surface of the burning fuel, or • The wall of the fuel container.

17. High expansion (HX) foam Particularly suitable for dealing with fires involving; • Basements • Ships holds • Machinery spaces • Cable ducting.

18. Considerations when using HX foam • Foam concentrate requirement • Siting of HX units • Level of injection • Ventilation • Maintaining the foam • Entering the compartment • Hazards in HX foam.

19. Loss of senses, vision, direction and hearing • DSU`s, alarms and evacuation signals will be very difficult to hear • Penetration of light is severely restricted • Heat transmission is reduced • Possibilities of pockets of trapped gas • Unable to observe damage to structure and obstructions.

20. Safety precautions when working in HX foam • Breathing apparatus essential • Communications to be used at all times • Guidelines must always be used • Only enter for rescue or urgent need • Ensure the fire is extinguished before entering • Back up agents to be standing by.

21. Foam making equipment The aspirating devices used to produce foam are divided into three basic categories; • Generators for LX foam • Foam making branches for LX foam • Generators for HX foam.

22. On/Off control valve Air intake holes Outlet nozzle Standard instantaneous coupling Semi circular baffles Turbulence chamber Low expansion (LX) foam making branch Finished foam. Foam solution Downstream orifice plate Strainer Dispersal disc Foam making tube Upstream orifice plate

23. Hermaphrodite induction coupling supplying foam compound Non return valve Improver Inline inductor Nozzle Foam Solution. Water Female coupling Filter By pass valve Male coupling

24. Fan Fine mesh screen Foam solution Air Air Flexible ducting Finished Foam. Air Foam solution Air Air Operating principles of HX generator

25. ConfirmationAssessments will be based on this lesson and the corresponding study note Learning Outcomes • Describe the principal methods by which foam extinguishes a fire • State the types of foam concentrate in use • List the types of foam making equipment in use • Identify the considerations when using foam making equipment.

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