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In the oil and gas industry, risk assessments are conducted to ensure the implementation of risk control measures, thus preventing the realization of hazards and maintaining a safe working environment. Consequently, understanding the meaning and relevance of common industry terms related to hazards is crucial. The following information provides explanations of basic terms used in this context.

2.1.1 Flash Point: The flash point of a volatile liquid represents the lowest temperature at which it can vaporize and form an ignitable mixture when mixed with air. Storing a fluid at a temperature below its flash point effectively prevents the formation of ignitable vapors.

2.1.2 Vapour Density: Vapour density measures how dense a vapor is in comparison to air. Comparing a vapor’s density with air helps determine whether it will rise or fall when released into the atmosphere. Vapors with a density below 1 will rise as they are lighter than air, while those with a density above 1 will fall as they are heavier than air. For example, propane, a type of Liquefied Petroleum Gas (LPG), has a density of 2.0, making it heavier than air, causing propane vapor to fall. In contrast, methane (liquefied natural gas) has a density of 0.717, making it lighter than air, causing methane vapor to rise. Understanding vapour density is essential for placing gas detection equipment and determining general ventilation requirements.

2.1.3 Vapour Pressure: Vapour pressure is the pressure measured in pascals (Pa) that results from the process of evaporation. Higher vapour pressure indicates a faster evaporation rate and a greater concentration of vapors. Substances with high vapour pressure at normal temperatures are considered volatile.

2.1.4 Flammability: Flammable vapors pose the risk of explosions, with varying levels of flammability. Flammability can be categorized as follows:

  • Flammable: Describes a product that is easily ignitable and capable of rapid burning.
  • Highly Flammable: Describes a product with a flash point below 21°C but not classified as extremely flammable.
  • Extremely Flammable: Describes a product with a flash point lower than 0°C and a boiling point of 35°C or lower.

2.1.5 Fire Triangle: A fire requires the presence of three elements: a source of fuel, a source of heat or ignition, and oxygen, forming the “fire triangle.” If any of these elements is eliminated, a fire cannot start or continue.

Within the fire triangle, when the source of fuel is a vapor, it must fall within a specific percentage range in comparison to air to burn. The “too rich” atmosphere has an excess of flammable vapor, while the “too lean” atmosphere lacks sufficient flammable vapor. The range between these limits is known as the flammable range. For example, methane gas has a flammable range between 4.4% and 15-17%. An atmosphere within this range is flammable, emphasizing the need to control it. Purging storage tanks with inert gases like nitrogen helps maintain a non-flammable atmosphere.

2.1.7 Toxicity: Toxicity has two uses:

(a) Denoting the capacity of a substance to harm a living organism. (b) Indicating the adverse effects caused by a chemical, which is detailed in the Material Safety Data Sheet accompanying the chemical.

Further descriptions related to toxicity include:

  • Acute Toxicity: Describes the immediate effects of a substance on a person, resulting from either a single exposure or multiple exposures within a short timeframe (e.g., 24 hours or less), such as radiation exposure.
  • Chronic Toxicity: Refers to the long-term adverse effects caused by a chemical.
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