- Define EACH of the following, stating an example in EACH case where a fire could be caused:
(a) spontaneous combustion;(4)
(b) flash point;(3)
(c) auto ignition temperature.(3)
What is Spontaneous combustion?
Spontaneous combustion is a phenomenon where a material ignites and bursts into flames without an apparent external source of ignition. This occurs due to internal chemical reactions within the material that generate enough heat to reach the material’s ignition temperature.
1. Spontaneous combustion | Ignition, Heat, Oxygen – Britannica
2. Self-Heating and Spontaneous Combustion – Metropolitan Fire Service
Key Points:
- Self-Heating: The process begins with self-heating, where the material undergoes exothermic reactions (reactions that release heat) due to factors like oxidation, fermentation, or other chemical processes. 1. Spontaneous combustion – Wikipedia en.wikipedia.org
- Thermal Runaway: If the heat generated cannot dissipate effectively, the temperature of the material continues to rise, leading to thermal runaway, a self-accelerating process where the heat buildup increases the rate of reaction and further heat generation. 1. What is thermal runaway in lithium-ion batteries – Gasmet Technologies www.gasmet.com
- Autoignition: Eventually, when the material’s temperature reaches its ignition point, it will spontaneously ignite and combust in the presence of oxygen. 1. Spontaneous combustion – Wikipedia en.wikipedia.org
Factors Contributing to Spontaneous Combustion:
- Material Properties: Some materials are more prone to spontaneous combustion due to their chemical composition and physical properties. These include:
- Oily rags and fabrics contaminated with drying oils or paints 1. Rise In Fires Due To Improper Disposal Of Oily Rags | Essex CT www.essexct.gov
- Coal and other carbonaceous materials 1. Spontaneous combustion liability of coal and coal-shale: a review of prediction methods | International Journal of Coal Science & Technology – SpringerLink link.springer.com
- Hay, straw, and other organic matter 1. Hay and Straw Barn Fires a Real Danger – Agronomic Crops Network agcrops.osu.edu
- Certain chemicals, like finely divided metals or pyrophoric substances 1. What are Spontaneously Combustible Substances? – Storemasta Blog blog.storemasta.com.au
- Environmental Conditions:
- High ambient temperatures 1. Spontaneous combustion – Wikipedia en.wikipedia.org
- Poor ventilation, preventing heat dissipation 1. Spontaneous combustion – Wikipedia en.wikipedia.org
- Presence of moisture, which can facilitate certain chemical reactions 1. Spontaneous combustion – Wikipedia en.wikipedia.org
Examples of Spontaneous Combustion:
- Oily rags left in a pile can ignite due to the oxidation of the oil. 1. Rise In Fires Due To Improper Disposal Of Oily Rags | Essex CT www.essexct.gov
- Haystacks can spontaneously combust due to bacterial fermentation generating heat. 1. Spontaneous combustion – Wikipedia en.wikipedia.org
- Coal piles can ignite due to oxidation reactions, especially in the presence of moisture. 1. Modeling of Coal Spontaneous Fire in A Large-Scale Stockpile ijtech.eng.ui.ac.id
Prevention of Spontaneous Combustion:
- Proper Storage: Store materials prone to spontaneous combustion in well-ventilated areas, away from heat sources and moisture. 1. Spontaneous combustion – Wikipedia en.wikipedia.org
- Limit Pile Sizes: Avoid storing large quantities of these materials in confined spaces, allowing for adequate heat dissipation.
- Regular Inspections: Inspect stored materials regularly for signs of self-heating, such as an increase in temperature or the presence of smoke or odors.
Spontaneous combustion is a rare but potential hazard that can be mitigated through proper handling, storage, and awareness of the materials prone to this phenomenon.
Examples in marine engineering
Let’s explore some instances where spontaneous combustion can pose a risk in the marine engineering context:
- Oily Rags and Waste:
- Oily rags and other materials contaminated with lubricating oil, fuel oil, or cleaning solvents can undergo oxidation reactions when exposed to air. This process generates heat, and if the heat cannot dissipate efficiently, it can lead to spontaneous combustion. 1. Spontaneous Combustion: Be careful with oily rags and absorbents – New Pig Corporation www.newpig.com2. Restaurant Fires: 5 Tips for Handling Greasy Rags (to Prevent Spontaneous Combustion) societyinsurance.com
- Prevention:
- Store oily rags and waste in designated metal containers with self-closing lids. 1. Prevent Structure Fires By Properly Discarding Oil And Stain Soaked Rags – City of Mill Valley cityofmillvalley.org
- Dispose of them regularly according to proper waste management procedures.
- Insulation Materials:
- Some types of thermal insulation, particularly those made of organic materials or containing combustible components, can be prone to spontaneous combustion under certain conditions.
- Prevention:
- Choose insulation materials with low flammability ratings.
- Ensure proper installation and avoid contact with heat sources or electrical wiring.
- Inspect insulation regularly for signs of damage or deterioration. 1. Key steps in preventing engine room fires – The International Institute of Marine Surveying www.iims.org.uk
- Coal and Other Carbonaceous Materials:
- While coal is less commonly used as a fuel in modern ships, it’s still present on some vessels. Coal can undergo slow oxidation, especially when damp, generating heat and potentially leading to spontaneous combustion in large piles or bunkers. 1. Influence of mudstone on coal spontaneous combustion characteristics and oxidation kinetics analysis | Scientific Reports – Nature www.nature.com
- Prevention:
- Maintain proper ventilation in coal storage areas.
- Avoid moisture accumulation in coal bunkers.
- Monitor the temperature of coal piles regularly.
- Batteries:
- Certain types of batteries, especially lithium-ion batteries, can experience thermal runaway and spontaneous combustion under certain conditions, such as overcharging, physical damage, or manufacturing defects. 1. Why do lithium-ion batteries catch fire? – the Fire Protection Association. www.thefpa.co.uk
- Prevention:
- Handle and store batteries according to manufacturer’s instructions.
- Avoid overcharging or exposing them to high temperatures.
- Install appropriate safety devices like thermal fuses and ventilation systems in battery rooms.
- Other Potential Sources:
- Chemical Spills: Spills of certain chemicals, especially those that react readily with oxygen or moisture, can create a risk of spontaneous combustion.
- Improperly Stored Combustibles: Rags soaked in linseed oil, organic fertilizers, and other combustible materials stored in confined spaces without proper ventilation can also ignite spontaneously. 1. Linseed Oil and Spontaneous Combustion: Take it seriously. | Popular Woodworking www.popularwoodworking.com
General Precautions:
- Maintain good housekeeping practices in all machinery spaces and storage areas, ensuring cleanliness and proper ventilation. 1. Key steps in preventing engine room fires – The International Institute of Marine Surveying www.iims.org.uk
- Regularly inspect stored materials, especially those prone to spontaneous combustion, for signs of heat buildup, smoke, or odors. 1. Key steps in preventing engine room fires – The International Institute of Marine Surveying www.iims.org.uk
- Store flammable and combustible materials in designated areas, away from heat sources and ignition sources.
- Train crew members on the hazards of spontaneous combustion and the proper handling and storage of susceptible materials.
By being aware of the potential sources of spontaneous combustion and implementing preventive measures, the risk of fire incidents on board can be significantly reduced, enhancing the safety of both the crew and the vessel.
What is flash point?
Flash point is the lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near the surface of the liquid. When this mixture encounters an ignition source (like a spark or flame), it will briefly ignite or “flash.”
1. Flash Point Explained | Lazar Scientific, Inc.
2. www.oshaoutreachcourses.com
3. Flash point | Temperature Measurement, Ignition Temperature & Flammability | Britannica
Key Points about Flash Point:
- Safety Indicator: Flash point is a critical safety parameter, particularly when handling flammable liquids. The lower the flash point, the more easily the liquid can ignite, posing a greater fire hazard. 1. Flash Point Analysis – ARO Scientific aroscientific.com2. Flammable and Combustible Liquids Overview – UCSD Blink blink.ucsd.edu
- Classification of Liquids: Flash point is used to classify liquids into categories based on their flammability:
- Flammable liquids: Flash point below 37.8 °C (100 °F)
- Combustible liquids: Flash point at or above 37.8 °C (100 °F)
- Relationship to Vapor Pressure: Flash point is directly related to a liquid’s vapor pressure. Higher vapor pressure means more vapor is released at a given temperature, leading to a lower flash point.
- Measurement: Flash point is determined through standardized tests, typically using either an “open cup” or “closed cup” apparatus. 1. Flash point | Temperature Measurement, Ignition Temperature & Flammability | Britannica www.britannica.com
Importance in Marine Engineering:
- Fuel Safety: Knowing the flash point of fuels like marine diesel oil (MDO) is crucial for safe handling, storage, and bunkering operations. 1. Flash Point of fuels to assess their flammability and safety characteristics – Petro Online www.petro-online.com
- Fire Prevention: By understanding flash points, engineers can implement appropriate safety measures to prevent fires and explosions in the engine room and other areas where flammable liquids are present.
- Regulatory Compliance: Flash point is a key parameter specified in fuel oil specifications and regulations like MARPOL Annex VI, ensuring the safe use of fuels on board vessels.
Remember: Flash point is not the temperature at which the liquid will continue to burn. For sustained combustion, the liquid needs to reach its fire point, which is typically higher than the flash point.
What is auto ignition temperature?
Autoignition temperature, also known as self-ignition temperature or kindling point, is the lowest temperature at which a substance will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark.
1. Auto-ignition Temperature | SKYbrary Aviation Safety
Key Points:
- Activation Energy: This temperature provides the necessary activation energy to initiate the combustion reaction within the substance. 1. Autoignition temperature – Wikipedia en.wikipedia.org
- No External Ignition Source: Unlike the flash point, which requires an external ignition source, autoignition occurs solely due to the substance’s internal heat reaching a critical point. 1. Auto-Ignition Temperature: Understanding the Science behind Spontaneous Combustion www.purkh.com
- Pressure Dependence: The autoignition temperature of a substance decreases as the pressure increases. 1. Autoignition temperature – Wikipedia en.wikipedia.org
- Oxygen Dependence: Similarly, a higher oxygen concentration can also lower the autoignition temperature. 1. Auto-ignition Temperature | SKYbrary Aviation Safety skybrary.aero
Relevance in Marine Engineering:
- Fire Safety: Knowledge of autoignition temperatures is crucial for handling and storing flammable materials onboard a vessel. It helps in assessing the fire risk and implementing appropriate safety measures to prevent accidental ignition. 1. Auto-Ignition Temperature: Understanding the Science behind Spontaneous Combustion www.purkh.com
- Engine Operation: In diesel engines, the autoignition temperature of the fuel is a crucial factor in the combustion process. The high compression in the cylinder raises the air temperature above the fuel’s autoignition point, causing it to ignite spontaneously without the need for a spark plug.
- Hazardous Environments: Certain areas on a ship, like engine rooms or cargo holds containing flammable materials, can have elevated temperatures. Understanding autoignition temperatures helps identify potential fire risks and take preventive measures. 1. Fuel leaks and unshielded hot spots in engine rooms – Bernhard Schulte Shipmanagement www.bs-shipmanagement.com
Comparison with Flash Point:
- Flash Point: Lowest temperature at which a liquid releases enough vapor to form an ignitable mixture with air near its surface, requiring an external ignition source to ignite. 1. Flammable Liquids: Difference Between Flash Point and Auto-Ignition Temperature blog.storemasta.com.au
- Autoignition Temperature: Lowest temperature at which a substance spontaneously ignites without any external ignition source. 1. Auto-ignition Temperature | SKYbrary Aviation Safety skybrary.aero
Remember: The autoignition temperature is generally much higher than the flash point for a given substance. Both parameters are important for assessing fire hazards and implementing appropriate safety measures.