Fire

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FIRE

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Fire fighting on board ship can be defined in three separate categories:

Fire protection, by design features in the construction of the vessel and subsequent control of human behaviour

Fire Detection, using artificial systems or human senses.

Fire suppression using a number of fixed or portable systems.

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All fire fighting starts with the idea of what is needed for FIRE

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All fire fighting breaks the triangle

REMOVAL

Or

STOPPAGE

Reduce to less than 10% Oxygen

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Construction of ships

materials

details of construction as defined in SOLAS bulkheads (strength, Fire rating, position)

Air trunking including fire flaps

Electrical protection

Human behaviour

Good Supervision

Training

FIRE PROTECTION

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Fire detection systems are compulsory in ships which have periodically unattended machinery spaces.

FIRE DETECTION

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A fire detection system consists of the following elements:

Human observation

Manual fire alarms

Automatic Fire detectors-smoke, flame, heat (gas, H2S)

Combinations of the above

For reference purposes Fire detection system requirements are detailed in SOLAS CHAPTER II-2

FIRE DETECTION

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Human observation relies on the human senses:

Sight

Sound

Smell

Taste

Touch

FIRE DETECTION

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Most Human observations can be mimicked by the following detectors

Sight-

Infra red flame detectors, sensing flicker patterns, smoke detectors using light sources in “go” or “no go” light transmission and reception.

Smell and Taste-

combustion products entering an ionized chamber.

Touch-

Heat detectors, including absolute temperature and rate of rise temperatures.

FIRE DETECTION

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Manual systems usually involve some form of manual fire patrol. The question about fire patrols is the only common question occurring in class 1 deck and class 1/2 motor.

Call points, a recognised route, regular communications, timing and record keeping are essential.

FIRE DETECTION

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Automatic Fire detection

An automatic fire detection system has the following components

1. Electrical feed, both normal and emergency (including battery backup)

2. Main control unit (usually housed in the wheelhouse( with repeater units

3. Fire detection sensors and manual call points

4. Electrical circuits to connect 1,2 and 3.

FIRE DETECTION

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Detector Units

Detector units detect outbreak of fire by sensing

Heat

Smoke

Flame

Detector heads are positioned throughout the vessel, in machinery, accommodation and in some cases, cargo spaces.

FIRE DETECTION

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Detector Units

On some systems each individual detector head has its own address, so that in the event of an alarm detection, the head position is indicated on the control panel and the seat of the fire is determined

Overall Fire alarms are automatically sounded, usually by the activation of one alarm.

FIRE DETECTION

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A simplified view of the layout of a fire detection system, featuring normal/emergency power supply, UPS,Loop,Zone Indicators, Alarms, Test switch and Fire Zones.

FIRE DETECTION

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Contacts in any detector head are normally open, and in the event of a fire they close and complete the alarm circuit.

Power supply is usually 24V and emergency UPS is provided by fully charged stand by batteries.

The emergency supply must be capable of powering the system for a mi9nimum of 18 hours on a cargo ship and 36 hours on a passenger ship.

FIRE DETECTION

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The choice of detector head to be fitted in the alarm circuit will depend on a number of factors:

1. Fire risk2. Position3. Area to be monitored4. Volume of space5. Height of compartment6. Atmosphere in space

Different types of detector head are used on common bases.

FIRE DETECTION

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Smoke detectors must not operate below 2% obscuration per metre, but must activate before 12.5% obscuration.

Heat detectors must not operate below 540C but must operate before 780C.

However, in certain cases the heat detector limits may be increased by 300C

FIRE DETECTION

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SENSOR OPERATING PERAMETERS

Type AREA ( MAX) DISTANCE APART

DistanceFrom Bulkhead

HEAT 37m2 9m 4.5m

SMOKE 74m2 11m 5.5m

FIRE DETECTION

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Smoke and heat detectors must also be sited to avoid stratification: that is the detector must not be blanketed by layers of hot air.

FIRE DETECTION

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In this case, the increasing convection air currents have created a flow of combustion products across the detectors.

FIRE DETECTION

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As shown, detector heads must be positioned to allow easy passage of combustion products in all fire scenarios

FIRE DETECTION

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HEAT DETECTION

BI METALLIC STRIP

FIRE DETECTION

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HEAT DETECTION

RATE OF RISE:

TWO BI METALLIC STRIPS

FIRE DETECTION

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HEAT DETECTION

RATE OF RISE:

TWO BI METALLIC

STRIPS

FIRE DETECTION

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HEAT DETECTION

RATE OF RISE:

TWO BI METALLIC

STRIPS

FIRE DETECTION

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HEAT DETECTION;RATE OF RISE:PNEUMATIC

FIRE DETECTION

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FIRE DETECTION

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FIRE DETECTION

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SMOKE DETECTION

IONISATION

RADIOACTIVE SOURCE

AMERICIUM

FIRE DETECTION

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NORMAL

In normal conditions, the Ions “flow” easily across the air gap and thus maintain an electric circuit.

FIRE DETECTION

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FIRE

In fire conditions, smoke particles slow down the flow of ions and the circuit is broken.

FIRE DETECTION

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SMOKE DETECTION: DEFLECTION OF LIGHT- “GO”

FIRE DETECTION

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NORMAL CONDITION “NO-GO”

FIRE DETECTION

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FIRE CONDITION “NO-GO”

FIRE DETECTION

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LIGHT OBSCURATION - PHOTO ELECTRIC CELL

FIRE DETECTION

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INFRA RED DETECTOR

Detects radiation in a particular narrow band –”flame flicker”

Can be confused by flickering lights, hence built in time delay.

FIRE DETECTION

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This multi wavelength flame detector is monitoring the flame generated when a hydrocarbon mixture burns.

FIRE DETECTION

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FIRE DETECTION

This slide shows how different components in a fuel mixture generate different radiation wavelengths-the different colours in a flame.

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FIRE DETECTION

The overall flame appearance consists of a number of wavelengths.

Most marine flame detectors detect the wave length of carbon dioxide produced in combustion ( just like human vision)

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FIRE DETECTION

The filter only allows wavelengths in a certain bandwidth to pass through-this prevents false alarms from other sources.

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However, certain other false alarms may be initiated by sunlight, engine room lighting or reflections from rotating equipment. In addition, the detector may be “blind” from smoke.

FIRE DETECTION

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This detector must not be used as a stand alone unit, but in conjunction with other types of detector.

Its positioning must be chosen carefully, usually above a slow speed engine.

FIRE DETECTION

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This detector senses the ultra violet spectrum of a flame and is less sensitive to false alarms.

FIRE DETECTION

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TESTING A SMOKE DETECTOR

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CABLE LAYOUT

LOOP and LINE

Monitoring

LOOP MONITORING

The continuity of the cable is checked by both circuits a-d and b-c.

In the event of either cable failing due to damage the an alarm sounds.

FIRE DETECTION

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CABLE LAYOUT

LOOP MONITORING

Failure modes-damage causes open or short circuit on cables.

Short circuit, no discrimination between faults and FIRE activation.

Open circuit, fault alarm on one wire

FIRE DETECTION

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CABLE LAYOUT

LOOP MONITORING

In each case faults must be examined immediately

Whilst the fault condition exists subsequent fire detection is inhibited

Easier for accurate fault detection, discriminates between fault and fire but more expensive.

FIRE DETECTION

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Line monitoring: Damage to loop

Short circuit shuts down the system and gives Fire alarm.

Open circuit raises fault indication

Less reliable, harder to pinpoint faults but cheaper.

FIRE DETECTION

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When the reference resistance becomes LESS than the end resistance ( due to heat effect on cables) the FIRE alarm sounds. When reference resistance is GREATER than the end resistance a Fault alarm sounds.

FIRE DETECTION

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Fire Zones

The system is subdivided into ZONES to allow easy identification of the seat of the Fire.

Clear information must be displayed near the panel which shows the actual location of the Fire source or the location may be directly displayed on a MIMIC panel.

FIRE DETECTION

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Fire Zones

Regulations covering Fire detection are set out in SOLAS Chapter II-2, Regulation 13, Section 1.

Point 1.15 concerns modifications made to detection systems post 10/94 and deals with single addressable heads.

Section 2 deals with Installation requirements including details of areas to be monitored.

FIRE DETECTION

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FIRE FIGHTING SYSTEMSCurrently, the classifications of Fires are as follows

Class A SOLIDS or Carbonaceous fires

Class B Liquids or LIQUIFIABLE solids

CLASS C Gases

CLASS D Metals

CLASS E Electrical Equipment

Class F Cooking Oil or Fat

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All fire fighting systems are used to either:

Remove Heat

Remove Oxygen

Remove fuel

or

CHAINBREAK-stop the chemical reaction

FIRE FIGHTING SYSTEMS

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IMO defines FOUR CLASSES of FIRE

Class A – cooling-use WATER

Class B- DO NOT USE water UNLESS you use a FINE FOG or MIST.

Class C –remove FUEL!!!

Class D- Chain breakers or smothering ( removal of Oxygen)

Class E – CO2 or Dry Powder

Class F - CO2 or Dry Powder


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How is Heat Removed from a Fire

WATER

Freshwater

Sprinklers, curtains and “Hi Fog”

Seawater (via fire-pumps)

Hydrants, hoses, coarse sprinklers (and drenchers!) and fire mains ( hoses, hydrants and nozzles)


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FIRE MAIN

A sea water supply system to fire hydrants is fitted to every ship. Several pumps in the engine room will be arranged to supply the system, their number and capacity being dictated by legislation (MCA for UK registered vessels as well as LLOYDS RULES)

An emergency fire pump will also be located remote from the machinery space and with independent means of power.

A system of hydrant outlets, each with an isolating valve, located around the ship, and hoses with appropriate snap-in connectors are strategically located together with fire hose nozzles.


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Fire Hose Nozzles

These nozzles are usually of the jet/spray type providing either type of discharge as required. All the working areas of the ship are thus covered, and a constant supply of seawater can be brought to bear at any point to fight a fire.

While sea water is best used as a cooling agent in fighting Class A fires it is possible, if all else fails, to use it to fight Class B fires.

The jet/spray nozzle would be adjusted to provide a fine water spray which could be played over the fire to cool it without spreading.


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International Ship Shore Connection

An international shore connection is always carried on board ship. This is a standard size flange which is fitted with a coupling suitable for the ship's hoses.


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FIREMAIN LAYOUT


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The fire main has a number of dedicated fire pumps:

Main fire pumps, located in the main machinery spaces

Emergency fire pumps remotely located and independently powered

In addition, isolation valves are fitted so that the main fire pumps and emergency fire pumps can independently pressurise the fire main

Further isolation valves so that the accommodation and main deck can be pressurised independently.


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Hydrants are located around the deck, and each hydrant is equipped with a Fire hose and adjustable fire nozzle.

Materials used, types of hydrant connection and further equipment are subject to CLASS rules,

SOLAS merely gives a broad definition of what should be fitted- class provides the technical expertise for the detailed construction.

Certain areas, such as the paint locker are protected by manually operated spray systems, supplied by the Fire main.


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Tankers and Passenger vessels have a requirement for constant pressurisation of the fire main using “ jockey” pumps and a pneumatic pressure system, with main fire pumps stated manually or automatically.

Tankers on specific operations, which may involve high sulphur fuel, can be equipped with water drencher systems to cover the accommodation and protect it from hydrocarbon gas or H2S releases

Other specalised vessels provide manual water curtains at lifeboat embarkation points.


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Automatic FRESH water spray

The automatic spray or sprinkler system provides a network of sprinkler heads throughout the protected spaces. This system may be used in accommodation areas, and in machinery spaces with certain variations in the equipment used and the method of operation.

The accommodation areas are fitted with sprinkler heads which both detect and extinguish fires. Sprinkler head is closed by a quartzoid bulb which contains a liquid that expands considerably on heating.


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Automatic FRESH water spray

When excessively heated the liquid expands, shatters the bulb and water will issue from the sprinkler head. A deflector plate on the sprinkler head causes the water to spray out over a large area.


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HEAD is pressurised by Fresh water

BULB keeps valve closed.

Heat causes alcohol inside bulb to expand, shatter bulb and water flows.


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FRESHWATER SPRINKLER SYSTEM


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EXPANSION

Supply for up to 200 sprinkler heads

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SPRINKLER HEADS

The different colours denote different operating temperatures, but the alcohol is the same, only the size of the air bubble changes.

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Typical low pressure sprinkler

system

NOT HIGH FOG


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HIGH FOG

Cool and smother, using the latent heat properties of water to cool, and expansion into steam to temporarily remove oxygen.

Devised by Marioff, from an initial requirement by the Belgian air force, Marioff converted a hydraulic system of 200 bar pressure to water in 1974.


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HIGH FOG

Development then followed on head technology, and pressures have reduced drastically. The following slide shows a “GL” approved hi fog system currently fitted to new build container ships.

A single stage low pressure centrifugal pump, with a screw inducer fitted in the eye takes suction direct from the domestic fresh water tank.


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The detail shown right, features the pump taking suction from the fresh water tank.

The system is manually operated locally or remotely. Pump is fed via EMS.

All operations are controlled by one panel, opening valves and starting pump.


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Hi Fog droplets are extremely small, increased surface area causes them to flash into steam, latent heat is absorbed, steam generated displaces oxygen.


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MARIOFF tested their Hi Fog systems on a carbonaceous fire, and estimated the use of 150 litres of water in a Hi fog system is as effective as 7000 litres in a sprinkler system:

46.67 to 1 !!!


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SMOTHERING

Removal of Oxygen

FOAM

Simple foam installation, with seawater mixing with foam compound(usually protein).


77Exact metering of foam compounds and water.


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Types of foam available for marine use:

Protein base ( PF)

Flouro protein foam (FP)

Film forming fluoro protein foam (FFFP)

Synthetic detergent foam

Alcohol resistant foam-chemical fires

Aqueous film forming foam ( AFFF)


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A simple CO2 driven foam system


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Hi-Ex- has limited use due to lightness of foam. Convection currents can easily blow the foam away. Must be delivered from overhead nozzles

However you can breathe in the mixture, and there is a limited cooling and smoke clearing effect.


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CHAINBREAKERS

HALON

Still legal under IMO legislation but not UK legislation ( or other EU countries

plus CANADA)

NOVEC 1230 is an approved drop in

replacement.


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HALON is a CFC and so has the same OZONE depletion affect as R11 and R12.

NOVEC 1230 is a HALON replacement, using roughly the same pipeline layout, and same mass of fluid, with a slight change in head detail, and with an ODP and GWP of 0.

FM 200 requires roughly 1.5 times as much mass as HALON, has an ODP of 0 and a GWP of 1

PYROGEN has appeared briefly as a HALON substitute but has since disappeared.

Dry powder is also a chain-breaker and in addition acts as a smothering agent.


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Flammable Range

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The flammable range is relatively narrow, so that any new gas introduced into the space will either displace oxygen or remove hydrocarbon vapours.

This particular example is for crude oil, but the principle applies to all hydrocarbon based fuels.

Flammable Range

Fire

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