BURNING AND FIRE
Burning is a chemical process combining a substance and oxygen (a substance that supports burning). This releases heat and light (flames). Fire is not a controlled burning process.
For the combustion as a chemical process to begin or to last, certain conditions must be fulfilled:
- the presence of a combustible substance
- the presence of oxygen or a substance that supports burning
- sufficient ignition temperature.
Solid fuel comprises materials that, when ignited, release energy through combustion. Classified into non-flammable, flammable, and highly flammable, non-flammable substances don’t ignite even under high temperatures, while flammable ones burn in direct flame exposure. Uncontrolled combustion stages in solids, like wood, include ignition, burning, carbonation, and combustion. Higher-density substances generally have a higher flash point but generate higher burning temperatures. Dust particles, when ignited, can explode with temperatures up to 2500 °C. Some solids may self-ignite due to slow processes, like chemical changes or microorganism action. Prevention involves dissipating the heat generated by the exothermic reaction to curb self-ignition in susceptible materials like wet aluminum powder, cotton, and wood shavings.
The combustion of liquids involves vaporization and burning as gases and vapors, requiring a critical concentration above the liquid surface and a sufficient external heat source. The process begins with molecules separating from the liquid surface, forming a vapor cloud. Inflammation occurs when the critical concentration and external temperature are balanced (flash point). Complete combustion, known as the flame point, happens with increased temperature and vapor concentration. Flammable liquids in the maritime sector, categorized by flash points, include highly flammable (<-18 °C), medium flammable (-18 to +23 °C), and flammable (23 to 61 °C). This classification determines the fire protection level for ships and cargoes, emphasizing special measures for liquids with flash points below 61 °C.
Flammable gases and vapors
Combustion of gases and vapors requires a homogeneous mixture of combustible substances and oxygen, typically initiating with an explosion. Explosions involve a chemical change where a significant quantity of combustible material rapidly combines with oxygen, releasing substantial heat. Specific spatial ratios, known as explosive limits, must exist between combustible gases, vapors, and oxygen. The lower flammable limit (LFL) denotes the minimum for an explosion, while the upper flammable limit (UFL) signifies the maximum. Mixtures outside these limits are termed poor or rich. External heat is essential for the explosion to commence. Liquids with lower LFL or wider explosive ranges are considered more dangerous. Other substances can alter explosive limits, and the explosion’s destructive impact relies on flammable substance concentration. Explosions are categorized into deflagration (slow combustion expansion) and detonation (rapid expansion exceeding sound speed).
Oxygen (O2) is a colorless, odorless gas constituting 21% of the atmosphere. At higher temperatures, it readily reacts with other elements, facilitating combustion when combined with fuel. Sufficient oxygen enables complete combustion, while insufficient amounts lead to incomplete combustion, producing toxic carbon monoxide (CO) or pure carbon (C). In addition to atmospheric oxygen, unstable compounds, such as magnesium extracting oxygen from carbon dioxide (CO2), may contribute to combustion.
chemical factors. Electrical sources involve conductor temperature rise due to increased current or short circuits. Mechanical sources entail heat released by friction between solids. Thermonuclear reactions are rare fire causes, occurring mostly within nuclear facilities. Chemical sources involve exothermic reactions releasing heat. Direct heat transfer occurs through conduction, convection, and radiation. Conduction transfers heat between rigid bodies through molecule-to-molecule interaction, influenced by substance structure and thermal conductivity coefficient. Convection involves heat transfer through liquids and gases, crucial for extinguishing fires. Radiation is the most common heat transmission method, depending on body temperature, surface, color, and shape, with high radiative substances having high absorption capacity.
FIREFIGHTING PRINCIPLES AND FIRE CLASSIFICATION
Fires can be extinguished by addressing basic combustion conditions through cooling, separation, suffocation, or anti-catalytic action. Cooling involves lowering the temperature of the burning substance with an extinguishing agent, such as water for solids. Separation removes unburned combustible substances from the fire area, reducing fuel mass. Suffocation prevents oxygen supply to the fire by covering the burned substance with inert gases or non-combustible materials. Anti-catalytic action slows chemical processes using inhibition or intoxication. Fires are classified based on fuel state: Class A (solids), Class B (liquids), Class C (gases), Class D (flammable metals), and Class E (electrical fires). Proper classification guides the selection of suitable fire extinguishers, following ISO and NFPA standards.
FIRE DETECTION EQUIPMENT
The manual fire detector is used for the rapid transmission of fire information. It is usually an electromechanical switch with a glass/plastic cover in a red metal housing. When a fire is detected, the lid is broken, and the switch is turned, activating the ship’s audible signaling device and/or alerting the bridge of the location of the fire.
On ships, they are installed in corridors, control and auxiliary spaces, warehouses, storage areas, operating spaces, etc. The distance between them must ensure audibility on/within the ship (≈20m).
Automatic fire detectors include thermal, smoke, and light detectors, which are crucial for ship safety. Thermal detectors sense rapid temperature changes and are categorized into thermomaximal and thermodifferential. Thermomaximal detectors measure air temperature using principles like bimetal bending or pressure effects. Thermodifferential detectors measure thermal gradients. Smoke detectors, ionization or light-based, monitor smoke concentration. Ionization detectors use radioactive radiation, and light detectors measure light reaching a photoelement—flame detectors, infrared or ultraviolet, sense flames by specific light wavelengths. Infrared detectors collect filtered radiation, while ultraviolet detectors rely on electric conductivity when exposed to specific radiation wavelengths—fire alarm stations on the bridge display detector statuses. In case of fire, alarms activate, giving 2 minutes to verify or reset. The station then triggers the ship’s emergency system. The pipe fire alarm system, common on dry cargo vessels, uses a network to detect smoke particles. Fans maintain airflow with visual monitoring. These systems enhance safety by providing early warnings and efficient ship response mechanisms.
Properties of fire extinguishers
When selecting a fire extinguisher, considerations should include the fire’s characteristics and the extinguisher’s properties. Essential properties include non-toxicity, effectiveness, harmfulness, versatility, portability, and scope of use. Non-toxicity enhances safety, though achieving it during usage is challenging. Effectiveness is measured by the amount needed to extinguish a fire. Minimizing damage during extinguishing is crucial. Versatile extinguishers handle various fire types, while portability depends on technical simplicity. Scope of use considers conditions like low temperatures. Fire extinguishers are categorized by frequency of application: basic (water), dedicated (foam, CO2, powder, halogenated hydrocarbons), and supplementary (sand, blankets).
Water is a widely used and accessible firefighting agent, effective in extinguishing solid fires. Composed of two hydrogen atoms and one oxygen (H2O), water is stable and non-toxic, existing in liquid and gaseous states in nature. While suitable for high thermal fires, it reacts violently with certain metals (alkaline and alkaline earth metals) and substances like sulfuric acid. Water extinguishing methods include full jet, spray jet, and water mist. The full jet covers long distances but uses only a small amount of water. The spray jet is more water-efficient, making it suitable for close-range applications. Water mist, achieved with high pressure, is another method. Care is needed when using water on flammable liquids to prevent spreading. However, water conducts electricity, so caution is required near power sources.
Foam is a vital firefighting agent primarily used for extinguishing flammable liquids. The degree of expansion distinguishes heavy, medium, and light foams. Chemical foam, produced through acid salts’ reaction with alkaline substances, and air foam, a mixture of water, foam, and air, are common. Foam is neutral, non-harmful, and possesses desirable properties like stability, low freezing point, corrosion resistance, and fire resistance. Alcohol foams are used for specific flammable liquids. Powder, another fire-extinguishing agent, acts anti-catalytic by choking, cooling, and separating. Carbon dioxide (CO2) suffocates fires by reducing oxygen concentration, and halogenated hydrocarbons (halons) decompose to interrupt the burning process. Once effective but harmful to the ozone layer, Halons are phased out and replaced by alternatives.2.5. Fire protection for ships.
The principles of fire protection for ships
The principles of ship fire protection involve vertical and horizontal separation, restricting combustible materials, timely fire detection, limiting and extinguishing fires in their origin, providing access to fire locations, maintaining fire-fighting agent readiness, and reducing flammable cargo vapor ignition risks. Measures include preventing escape and accumulation of flammable liquids, limiting flammability, isolating ignition sources, introducing inert gases, and complying with SOLAS Convention regulations. Restrictions on airflow, limiting flammable liquid spillage, and controlling combustible material use are mandated. Fire containment employs fireproof bulkheads with doors. Fire extinguishing methods include deck water systems, gas extinguishing, high-expansion foam, and pressurized water systems. Ships have detailed fire protection plans covering systems, alarms, extinguishers, crew duties, and procedures.
Portable fire extinguishers
Portable fire extinguishers come with various agents (water, foam, powder, CO2, halons) for specific fire types. Water extinguishers suit wood, paper, and cloth fires but not near electrical sources. Foam extinguishers cover wood, flammable liquids, etc. Powder extinguishers work on all fires, relying on anti-catalytic action. CO2 extinguishers, pressurized gas, are effective for flammable liquids and electrical fires. Halogenated hydrocarbon extinguishers use halons under pressure, inhibiting combustion. Weight should not exceed 23 kg with proper labeling. Transportable extinguishers up to 250 kg exist, and deck firefighting systems on ships include fire pumps, hydrants, hoses, and nozzles, with specific requirements for pressure, placement, and connections to the mainland water supply.
Water extinguishing systems
Water extinguishing systems on ships can use spray water or operate independently. Pressure water spraying involves forming water mist droplets of various sizes, and the system consists of a pump, pressure vessel, piping, and nozzles. It effectively extinguishes high-pressure liquid fires by creating an emulsion that prevents or stops burning while cooling heated objects. However, drawbacks include residual water after extinguishing and potential vessel destabilization. The sprinkler system provides independent operation with a delivery pump, pressure vessel, pipeline, and sprinkler nozzle. The system activates based on maintaining constant freshwater pressure and uses glass containers or metal switches to release water at temperatures between 68 and 79 °C. Water mist fills the room when the nozzle leaks water onto the spray board. Conventional sprinkler systems operate at 5 to 8 bar, while high-pressure systems with pressures up to 25 bar or even 140 bar during extinguishing offer advantages such as minimal water usage, reduced damage to burned surfaces, and efficient heat transfer. However, high-pressure systems are technically more complex.
Carbon dioxide fire extinguishing system
The carbon dioxide (CO2) fire extinguishing system is installed in engine rooms, cargo areas, and pump spaces. It comprises pressurized CO2 vessels, safety valves, connecting pipes, pressure gauges, a control panel, an exciting gas tank, piping, and nozzles. The manually operated system can extinguish fires in one or more rooms. If inhabited spaces are involved, an alarm device precedes activation by at least 20 seconds. The release procedure involves selecting the room, opening compressed CO2 containers, and dispersing the gas through nozzles or a pipe fire alarm system. Continuous system monitoring, especially checking pressure on manometers, is essential due to potential gas leaks.
Foam fire extinguishing system
Foam fire extinguishing systems are used for fluids in engine rooms, pump rooms, tanks, and decks on tankers, and occasionally cargo areas for bulk cargo. Heavy foams are used in open spaces, while light foams are used indoors. Heavy foam systems consist of a seawater pump, foam tank, mixer, pipeline, and monitor, covering entire tank surfaces. Light foam systems include a seawater pump, pipeline, foam tank, and built-in foam dispenser, creating foam by injecting a mixture into the air stream. Monitors in heavy foam systems have a capacity of at least 3 l/min/m2, ensuring coverage of the maximum burnt surface with a 150 mm thick foam layer in 5 minutes. Light foam systems produce a minimum of 1 m of foam height per minute for the largest protected area.
Powder fire extinguishing system
Powder fire extinguishing system – chemical transport vessels, LNGs, paint tanks, and fires that are extinguished anti-catalytic. The system consists of a powder tank, a pressurized tank for propellant (N2 or CO2, 10 to 20 bar), and a pipe system with nozzles or cannons (protection of disembarkation points). The piping is made of rigid or flexible pipes. The dust leaks no later than 30 seconds after opening the gas tank.
The system can be portable (standalone) or installed. Contains up to 1000 kg of powder in multiple containers. One empties first, then the other, etc. The nozzles are either built-in or manual. Range 10 to 40 m—disadvantage: Lots of dust and reduced visibility.
After use, the system must be well-blown (cleaned) to prevent clogging of pipes and nozzles.
HALON fire extinguishing system
The powder fire extinguishing system is employed in chemical transport vessels, LNGs, and paint tanks designed for anti-catalytic fires. The system comprises a powder tank, a pressurized propellant tank (N2 or CO2), and a pipe system with nozzles or cannons. It can be portable or installed, with up to 1000 kg of powder in multiple containers. Nozzles have a range of 10 to 40 m. Disadvantages include the generation of a significant amount of dust and reduced visibility. After use, thorough cleaning is essential to prevent clogging of pipes and nozzles. The HALON fire extinguishing system, now prohibited due to ozone layer concerns, involves a liquefied gas tank, pipeline, and control cabinet, releasing HALON manually to fill the entire space within 20 seconds. Constant pressure monitoring is crucial for safety.
Personal fire protection
Personal fire protection means include:
- protective clothing
- protective footwear
- electric lamp
- breathing device
Protective clothing is crafted from waterproof material to shield the body from heat and burns, especially caused by steam. Its primary purpose is to facilitate brief work and stay in burned areas without hindering movement while efficiently dissipating body heat. Prolonged exposure to heat leads to pain, burns, skin discoloration, blistering, and tissue destruction. The clothing’s surface temperature depends on heat absorption, color, material, and exposure duration. Protective footwear, usually made of insulating materials like rubber, and solid helmets offer additional safety. Electric lamps for such environments must be spark-free with a minimum three-hour continuous battery life. Breathing apparatuses, crucial for protecting against toxic gases, vapors, and oxygen deficiency, include a pressurized air tank, reducing valve, pulmonary automaton, protective mask, and an audible signal weighing 8 to 12 kg. Some variants use tubes for air supply, pressurized by a compressor or portable tank.
BOAT FIRE EXTINGUISHING
Sources of fire
Various potential fire sources on board ships can be categorized into open flames (cigarettes, cookers), heated appliance surfaces (exhaust pipes, light bulbs), sparks from friction, electric sparks (switches, motors, short circuits), and self-ignition due to chemical/biological processes or temperature rise. The effectiveness of firefighting is directly related to the time elapsed from fire onset to extinguishing initiation. Hence, immediate action is crucial upon any suspicion of a fire. Thorough checks follow quick assessments, and if a fire is confirmed, the ship’s alert system should be activated promptly for a coordinated response.
Fire extinguishing in accommodation spaces
In the event of a fire on board ships, firefighting involves using portable fire extinguishers and sprinkler systems. The manual fire detector is activated when a fire is detected, and the fire extinguisher is manually operated. The sprinkler system is engaged if the temperature reaches 68 to 79 °C. After extinguishing the fire, it is crucial to promptly shut down the system to avoid further damage from seawater. If the fire persists, the fire alarm door closes remotely, shuts down ventilation, activates the deck fire extinguishing system, and adjusts valves for water supply. Rapid initiation of the extinguishing process is crucial, especially on passenger ships with flammable interiors. When entering the burned area, attention is given to thermal hazards, and precautions are taken against smoke and gases. Surrounding and extinguishing the fire from all sides is recommended, ensuring better visibility, safety, and reduced risk of poisoning and burns. Guards monitor adjacent rooms during extinguishing, emphasizing the importance of proper ventilation and safety measures.
Fire extinguishing in cargo areas and on deck
Fire-fighting systems like CO2 and deck systems are employed in cargo spaces, with CO2 common on dry cargo ships, excluding those carrying reactive chemicals. Upon a fire, ventilation is halted, openings sealed, and CO2 released, taking 5 to 15 minutes for effects. For stubborn fires, it may take days to extinguish fully. Deck fire extinguishers are activated if CO2 fails, attempting to reach the fire center. Containerized cargo presents challenges as CO2 struggles to penetrate sealed containers. Water quenching involves opening containers, using deck system hoses, and cooling from outside. On tankers, fire risks stem from other areas and accidents during cargo handling. For LNG, powder extinguishing follows gas supply cessation. Water use considers ship stability, and draining is attempted. Navigation adjustments, speed reduction, and downwind sailing aim to manage fire conditions at sea. Immediate ship abandonment is advised for ineffective interventions. In all cases, safety measures prioritize crew well-being and environmental impact.
Fire extinguishing in the engine room
The engine room poses a higher risk of fire on ships due to flammable liquids, high temperatures, and potential leakages. Combustible liquid fires, especially those from high-pressure fuel lines, are a significant threat. Minor fires are tackled with portable and transportable extinguishers, using powder and CO2 near electrical sources and foam in other cases. Gas systems like CO2 or HALON are employed for larger fires, evacuating personnel, and closing fuel supplies. Entry after gas extinguishing is delayed for safety, and subsequent ventilation is crucial. Foam systems require rapid coverage of the entire burned area but may necessitate additional interventions with portable extinguishers or water. Water spray systems are used sparingly, considering minimal water use, and are employed as a last resort or in urgent situations, such as with hazardous cargo. The post-extinguishing process involves thorough ventilation to replace air multiple times. Prompt and appropriate response strategies are critical for mitigating engine room fires on ships.
The danger of poisoning and suffocation
On ships, the potential for poisoning, harmful gases, or oxygen deficiency exists, primarily caused by various poisons that affect health through inhalation, ingestion, or contact. Inhalation poisons include dust, fumes, fogs, vapors, and gases, each categorized by their effects on bodily functions, such as enzyme inhibition or damage to organs like the blood, liver, kidneys, and nervous system. Maritime transport commonly encounters irritants, suffocates, intoxicants, and blood poisons. Irritants cause respiratory distress, while suffocators obstruct oxygen supply, leading to symptoms like headache and dizziness. Intoxicants affect the nervous system, causing dizziness and movement disorders. The impact of poisons depends on factors like concentration, duration of exposure, and individual resistance. Monitoring devices, such as gas trackers and handheld detectors, are crucial for detecting gas presence. Reduced oxygen levels can lead to fatigue, fainting, and, at extreme levels, rapid death. Safety measures involve evacuating endangered individuals from low-oxygen areas, resuscitating them, and using instruments to measure oxygen levels in critical situations.
Maintenance, inspection, and training
The fire system maintenance plan outlines procedures for maintaining various ship fire protection systems, including deck fire protection, built-in fire alarm and protection systems, ventilation systems, emergency fuel supply closures, fire doors, general alert systems, emergency breathing apparatus, and firefighting equipment. Passenger ships additionally cover Low-location lighting and the Public address system. Tailored to ship types, the plan ensures crew training, aligning with abandonment exercises and a Training manual. The manual encompasses precautionary measures, fire detection and extinguishing procedures, alarm system use, fire extinguisher and system operation, fire door handling, smoke protection, and evacuation instructions. The General Fire-Fighting Plan details equipment locations, control stations, fireproof bulkheads, alarms, space layouts, access routes, ventilation, firefighting tools, and maintenance instructions.