Fire Prevention Techniques in Ship
Fire safety tips and tricks!
Fire Safety Onboard
Fire is one of the biggest threats on board ships. If fire is not detucted on time, it could have disastrous consequences. As a watch keeper, it is your responsibility to take necessary precautions to prevent fire on board.
On completion of this topic, you will able to explain the fire chemisty, recognize the fire hazards.
Describe how fire start and spread state the various classes of the fire and the fire fighting methods. Describe how ship structures are designed to prevent the spread of fire. Explain fire alarm system, fire detectors, and fixed fire extinguishing systems. Identify portable fire extinguishers and realize the Shipboard fire fighting organisation.
Fire is an oxidation process. During this process, a flammable substance combines with oxygen in the presence of heat energy to give off heat and light. When any one of the elements is absent, the fire extinguishes.
When any one of the elements is absent, the fire extinguishes.
The fire triangle
Fuel, heat and oxygen are the three components of fire. Fuel refers to any combustible solid, liquid or gas.
Heat refers to energy capable of starting combustion. The source of heat energy can be a lighted fire, static electrical discharge, short circuit, heat arising from metal to metal contact without lubrication and so on. Oxygen is present in the atmosphere and its percentage is 21 percent.
The fire does not spread, when any one of these three components is absent.
Ignition phase
when there is sufficient air-vapour mixture and the temperature of the substance exceeds its ignition point, the fire starts. This fire can be due to an external heat source, auto ignition or spontaneous ignition. Spontaneous ignition occurs when certain materials become warm during oxidation producing more heat, which accelerates the oxidation process. In the ignition or 'incipient' phase, heat flows back to the material due to radiation. It results in a chain reaction enabling the components to sustain fire.
Developing phase
During the developing phase, the flame spreads on the surface of the material. After sufficient heating, it gives off vapours, which act as a source of heat. Solids and liquids covert to vapour state before combustion. In case of flammable gases, there is a high risk explosion, because the combustion process takes place at an extremely fast rate. The burning speed depends on the rate at which the heat source gives off the vapours, and its combustlibility. Patrol has a very high surface burning speed, while wood has a low surface burning speed.
Absolute fire phase
in this phase, the heat spread on the surface of the material pentrates into the depth of the solid or liquid. Intense flammable vapour will be generated at this stage.
Burning out Phase
The fire continues to burn, until it consumes most of the vapor. In the burning our phase, most of the fuel gradually burns out and the fire 'dies' thereafter.
The fire tetrahedron
The base of a fire tetrahedron represents the fourth component in a fire triangle. It is the 'chain reaction' due to the molecular combination of fuel, oxygen and heat energy. When you break the chain reaction, fire does not spread.
- Halon gas can break the chain reaction.
- Halon gas also known as vaporizing liquids, halogenated hydrocarbons BCF, Halon 1211 and BTM, Halon 1301.
- BCF has low vapour storage pressure and is light weight
- BCF is 40% more effective than CO2
- Halon extinguisher suitable for Class C and Class D fires
- Destroys ozone layer, not environment friendly
0 Comments