Service Delivery 3 Foam

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

Learning Outcomes At 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.

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.

Isolation Dilution Interception. Vapours Foam blanket

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

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

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.

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.

Differing foam expansions.

Low expansion foam Up to 21 metres throw.

High expansion foam Negligible throw.

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

Production of finished foam.

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;

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

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

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.

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.

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.

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

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

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

Foam solution Air FanFine mesh screen Operating principles of HX generator Flexible ducting Finishe d Foam.

Confirmation Assessments 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.

THE END