sasasa

HIGH EXPANSION FOAM SYSTEM

12DE

1004 Saiesh

1005 Brembley

1006 Russell

1007 Mukesh

The Fire Triangle

Three components

required for combustion

Fuel to vaporize and burn

Oxygen to combine with fuel vapour

Heat to raise the temperature of the fuel vapour to its ignition temperature.

Two important factors to remember in preventing and extinguishing a fire:

i) If any of the three components are missing, then a fire cannot start.

ii) If any of the three components are removed, then the fire will go out.

The Fire Tetrahedron

solid figure with four triangular faces

shows the chain reaction and each face touches the other three faces.

The basic difference - illustrates how flaming combustion is supported and sustained through the chain reaction of the oxidation process.

VARIOUS SYSTEMS USED ONBOARD FOR FIGHTING FIRE

HIGH EXPANSION FOAM SYSTEM

CO2 SYSTEM

SPRINKLER & SPRAYER SYSTEM

HALON SYSTEM

WHAT is FOAM ?

combination of three materials:

Water

Air

Foam making agent

formed by mixing the foam-making agent with water to create a foam solution.

foam bubbles created by introducing air into the foam solution through aerating devices.

Two most common concentrations are 3% and 6% foams.

HOW IS FOAM GENERATED ?

A constant amount of foam concentrate is added to water by means of a proportioner.

The resulting mixture of water/foam concentrate is expanded with air in the foam generator.

FOAM CONCENTRATOR

SEA WATER EDUCTOR

AIR IN

FAN

SPRAY NOZZLE

TO ENGINE ROOM

NYLON MESH

The Induction rate

specifies the percentage ratio of foam concentrate added to water.

At 3% induction rate, for example, 3 parts of foam concentrate are mixed with 97 parts of water.

Film formation

The foam produces a very thin aqueous film on non polar liquids

This film floats ahead of the foam and provides for its excellent flowing, extinguishing and re-ignition inhibiting properties.

Aqueous film

(AFFF effect)

produced by the polymer film formers contained in the foam when extinguishing polar hydrocarbons (e.g alcohols, ketones, ester).

The film floats as an insulating protective layer between the foam destroying alcohol and the foam cover above.

Polymer film

HOW FOAM EXTINGUISHES FIRE ?

Separating effect

The closed foam cover separates the combustion zone from the ambient air.

Cooling effect

The flammable material is cooled down by the water/ foam solution discharged by the foam.

Cover effect

The closed foam cover stops any further gas evaporation from burning materials, i.e. flammable gases

foam forms a blanket on the surface of flaming liquids

Repression effect

Flooding spaces, channels, plant parts, etc. with high or medium expansion foam represses the atmospheric oxygen and flammable gases necessary for the combustion process.

Insulation effect

foam insulates flammable material which has not yet caught fire

Foam Characteristics

Knockdown Speed and Flow- ability to spread across a fuel surface or around obstacles

Heat Resistance-able to resist the destructive effects of heat radiated from any remaining fire

Vapour Suppression. capable of suppressing the flammable vapours to break the fire triangle.

Alcohol Resistance-foam blankets that are not alcohol-resistant will be destroyed if used on alcohol-based cargoes.

cohesive properties- to stick together sufficiently to establish and maintain a vapour tight blanket

light enough-to float on flammable liquids, yet heavy enough to resist winds

Types of Foams

Chemical foam

formed by mixing together a solution of an alkali, an acid, water and a stabilizer.

forms a foam or froth of bubbles filled with carbon dioxide gas.

7 to 16 volumes of foam are produced for each volume of water.

Needs a device called a foam hopper or separate tanks

Mechanical (Air) Foam

produced by mixing a foam concentrate with water to produce a foam solution.

The bubbles are formed by the turbulent mixing of air and the foam solution.

TYPES OF MECHANICAL FOAMS

Protein Foam

produced by the hydrolysis of waste protein material, such as protein-rich animal waste and vegetable waste that is hydrolyzed

Fluoroprotein Foam (FP).

formed by the addition of special fluorochemical surfactants with protein foam

Film Forming Fluoroprotein Foam (FFFP)

combination of fluorochemical surfactants with protein foam

release a film on the surface of the hydrocarbon.

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Aqueous Film Forming Foam (AFFF)

combination of fluorochemical surfactants and synthetic foaming agents

film spreads rapidly causing dramatic fire knockdown.

Alcohol Resistant-Aqueous Film Forming Foam (AR-AFFF)

combination of synthetic stabilizers, foaming agents, fluorochemicals and alcohol resistant additives

offers good burnback resistance, knockdown and high fuel tolerance on both hydrocarbon and alcohol fuel fires.

Synthetic Foam

made up of alkyl sulfonates.

It foams more readily than the proteins and requires less water

important where the water supply is limited

Categories of foam sytems

Low Expansion Foams

expansion ratio of 12:1 when mixed with air

effective in controlling and extinguishing most flammable liquid (Class B) fires

typically used on tanker deck foam systems

Mid Expansion Foams

expansion ratio of between about 20:1 to 100:1

truly three dimensional; it is measured in length, width, height, and cubic feet

High-expansion foam

designed for fires in confined spaces

Heavier than air but lighter than oil or water

Limitations on the Use of Foam

Because they are aqueous (water) solutions, foams are electrically conductive

Like water, foams should not be used on combustible-metal fires.

not suitable for fires involving gases and extremely low temperature liquids.

If placed on burning liquids whose temperatures exceed 100C (212F), the water content of the foam may cause frothing, spattering or slopover.

Sufficient foam must be available.

Advantages of Foam

effective smothering agent and provides cooling effect.

sets up a vapor barrier that prevents flammable vapors from rising

Can be used on Class A fires because of its water content.

effective in blanketing oil spills

uses water economically

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most effective extinguishing agent for fires involving large tanks of flammable liquids.

can be made with fresh water or seawater, and hard or soft water

does not break down readily and extinguishes fire progressively

Foam stays in place, covers and absorbs heat from materials that could cause re-ignition

Foam concentrates are not heavy, and foam systems do not take up much space.

PRACTICAL ISSUES

Water Temperature and Contaminants

more stable when generated with lower temperature water.

temperature range 1.7C to 26.7C

Combustible Products in Air

It is desirable to take clean air into the foam nozzle at all times

Water Pressures

Nozzle pressures should be held between 3.4 bar and 13.8 bar (50 and 200 psi)

Non-ignited Spills

Where flammable liquids have spilled, fires can be prevented by prompt coverage of the spill with a foam blanket

Electrical Fires

not generally recommended for use on electrical fires

Vaporized Liquids

not recommended for use on materials that react with water, such as magnesium, titanium, potassium etc.

High Expansion Foam System and Equipment

FOAM GENERATOR

Delivers large quantity of expanded foam by blowing air through a screen

Because of high expansion ratio requires little water

Foam Generator

FOAM GENERATOR SCREEN

FOAM GENERATOR SCREEN

FOAM GENERATOR SCREEN

1) Proportioning Devices

Eductor

most common form of proportioning equipment works on the Venturi principle.

extremely reliable and simple pieces of equipment

Around-the-Pump Systems

an eductor is installed on the discharge side of the water pump

water flow causes a vacuum that picks up and introduces the foam concentrate into the water

Balanced Pressure Foam Proportioners

extremely versatile and accurate

The principle of operation based on the use of a modified venturi proportioner commonly called a ratio controller.

2) Foam Nozzles

designed to air aspirate (expand) the foam solution and form finished foam.

High expansion foam nozzles expands foam in excess of 100:1, when high expansion foam concentrates are used.

3) Foam Monitors

are permanently-installed foam discharge units

capable of being aimed and projecting large quantities of foam substantial distances.

normally mounted on a rotating base (360-degree circle)

4) Valves and Piping

must be adequately designed to match the flow rates of the equipment, and a thorough understanding of the system

control valves is critical for quick and effective operation of the system

Color coding of the valves

4) Valves and Piping

5) Foam Concentrate Storage

stored in tanks ready to supply the proportioning system

The concentrate tank should be kept filled with liquid halfway

The tank should be kept closed to the atmosphere

SOLAS REQUIREMENTS

FOAM CONCENTRATE

Foam concentrates to be of the type approved by administration

Capable of rapidly discharging foam @ at least 1 m in depth per minute

Volume of foam = 5 x volume of largest space

Expansion ratio not to exceed 1000:1

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INSTALLATION REQUIREMENTS

System should provide effective foam production and distribution

Foam generator delivery ducting to be protected against fire risk, withstand 925 deg C.

Foam delivery ducts to be constructed of steel having thickness > 5 mm

Dampers to be automatically operated by remote control

All system equipment to be readily accessible and simple to operate

ABS Requirements for Foam Extinguishing Systems

Design and Certification of Piping Components

All valves, fittings and piping to comply with the applicable requirements

be suitable for the intended pressures

Pipe and Pipe Joints

the wall thickness, type and design of the pipe joints to comply with the requirements

Materials

materials used in the system should not to be rendered ineffective by heat.

material to have a melting temperature higher than the test temperature specified in an acceptable fire test.

Pumps

should be tested in the presence of a Surveyor

Pressure Vessels

the tank is to be considered a pressure vessel and is to comply with the requirements as applicable.

System Component Certification

fixed fire-extinguishing system components are to be certified.

Accordingly, components such as foam system eductors, proportioners, monitors, nozzles, etc., are to comply with the certification requirements

STARTING PROCEDURE

AUTOMATIC START

Stop the supply fan and exhaust fan in the E/R.

Break the Destruct plate and push the system standby switch.

Alarm sound for evacuation in the E/R.

Start the Emergency fire pump manually.

After evacuation is confirmed push the foam discharge switch.

TO STOP;

Push the system stop switch.

Stop the Emergency fire pump.

MANUALLY START AT LOCAL SIDE.

Check all Valves.

Start the Emergency fire pump.

Check pressure gauge, indicate 4 bar.

Open valve and start foam liquid pump.

TO STOP:

Stop the Emergency fire pump.

Close the valves.

Example Calculation of the Capacity of Foam System for Oil Carrier Shipparticulars Beam = 14.5 m Length of cargo area = 56 m Length of largest cargo tank = 9 m Cargo deck area = 14.5 m 56 m = 812 m2 Horizontal sectional area of single largest tank = 14.5 m 9 m = 130.5 m2 Proposed monitor spacing = 9 m Area protected by largest monitor = 9 m 14.5 m = 130.5 m2

14.5 m

9m

56m

A case study

LESSONS LEARNT

Proper maintenance should be done including putting back the cover

Blowing/purging the line after hydraulic pressure testing

Inspection of the foam nozzle after test

Foam line on board to be pressure tested regularly

Draining the line to prevent accumulation of water

WHERE IS HIGH EXPANSION FOAM SYSTEM USED ?

ENGINE ROOM

PURIFIER ROOM

INCINERATOR ROOM

PUMP ROOM

PACKING OF FOAM CONCENTRATES

20 litresPlastic CanSize (ca. cm)38 x 38 x 18Tara ca. kg1,4SuitabilitySynthetic, ProteinNet weight approxSynthetic 20 Kg, Protein 23 KgStackable2 high, to 40C, shrink-wrapped onto a pallet

20 litresPlastic Can BlueSize (ca. cm)29 x 26 x 39Tara ca. kg1,2SuitabilitySynthetic, ProteinNet weight approx25 30 KgStackable2 high, to 40C, shrink-wrapped onto a pallet

200 litresValenthene BarrelSize (ca. cm)60 x 90Tara ca. kg21SuitabilitySynthetic, ProteinNet weight approx200 225 KgStackable2 high

1000 litresPalett ContainerSize (ca. cm)100 x 120 x 116Tara ca. kg80SuitabilitySynthetic, ProteinNet weight approxSynthetic 1040 Kg, Protein 1150 KgStackable2 high

TYPES OF HIGH EXPANSION FOAM SYSTEMS

TOTAL FLOODING SYSTEM

Maintenance and Inspection of System and Appliances.

Operational readiness

To be in good order and readily available for immediate use while the ship is in service.

Maintenance and Testing

should be carried out in accordance with the ship's maintenance plan.

Inspections should be carried out by the crew in accordance with manufacturer's maintenance and inspection guidelines

Monthly testing and inspections

Verify all control and section valves are in the proper open or closed position, and all pressure gauges are in the proper range.

Quarterly testing and inspections

Verify the proper quantity of foam concentrate is provided in the foam system

Annual testing and inspections.

visually inspect all accessible components

functionally test all fixed system audible alarms

flow test all water supply and foam pumps for proper pressure and capacity

Ensure all piping is thoroughly flushed with fresh water after service

test all system cross connections to other sources of water supply for proper operation

verify all pump relief valves, if provided, are properly set

examine all filters/strainers to verify they are free of debris and contamination

verify all control/section valves are in the correct position

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blow dry compressed air or nitrogen through the discharge piping

confirm the pipework and nozzles of high expansion foam systems are clear of any obstructions, debris and contamination

take samples from all foam concentrates carried on board and subject them to the periodical control tests

test all fuel shut-off controls connected to fire-protection systems for proper operation.

Five-year service

perform internal inspection of all control valves

flush piping with fresh water, drain and purge with air

check all nozzles to prove they are clear of debris

test all foam proportioners to confirm that the mixing ratio tolerance is within +30 to -10% of the nominal mixing ratio

TESTING OF FOAM SAMPLES

No Type of foam concentrate Minimum frequency 1All Fixed systems except protein based non- alcoholicWithin 3 years from the date of manufacture and every year thereafter. 2 All Fixed systems of protein based non- alcoholicAnnually. 3All factory-sealed portable containers excluding protein based Ten yearly. 4All factory-sealed portable containers of protein based concentrates Five yearly. 5All non-sealed portable containersWithin 3 years from the date of manufacture and every year thereafter

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