Transcript Service Delivery 3

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
Vapours
Foam blanket
Interception.
How foam extinguishes fire
• Cooling of the fuel
• Dilution of the surrounding air with
water vapour from evaporated foam.
Main properties
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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
This is the most widely used foam because;
• Can be projected over fairly long distances
• Spreads fairly quickly
• Is capable of forming a stable and secure
foam blanket.
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.
High expansion (HX) foam
Particularly suitable for dealing with fires
involving;
• Basements
• Ships holds
• Machinery spaces
• Cable ducting.
Considerations when using
HX foam
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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
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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
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.
On/Off control
valve
Standard
instantaneous
coupling
Air intake
holes
Turbulence
chamber
Semi circular
baffles
Outlet
nozzle
Finished
Foam
solution
foam.
Strainer
Upstream
orifice plate
Downstream
orifice plate
Foam
making
tube
Dispersal
disc
Low expansion (LX) foam making branch
Hermaphrodite induction coupling
Non return valve
supplying foam compound
Improver
Nozzle
Foam
Water
Male
coupling
Solution.
Filter
By pass
valve
Inline inductor
Female coupling
Fan
Air
Fine mesh
screen
Air
Foam
solution
Flexible
ducting
Air
Air
Air
Finishe
d
Foam.
Foam
solution
Operating principles of HX generator
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