Safety Technology Exchange Edition: Daily Question (2016.5.17)
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bg10.png Type: Short-answer question Question: [Fire Safety Technology] What is the flash point? What are the factors that affect flash point? The flash point is the lowest temperature at which a flash fire can occur on the surface of a liquid under specified test conditions. Flash ignition occurs when sufficient vapor is generated on the surface of a liquid and mixes with air to form a flammable gas, which then catches fire upon contact with a heat source. The flash point depends on the density of the flammable liquid, the air pressure at the liquid surface, as well as whether light components are present in the flammable liquid and their concentration. If the flash point of flammable liquids suddenly decreases during use, accidents involving the mixing of light oils or hydrolysis (in the case of certain synthetic oils) may occur, and this requires attention. The flash point of flammable liquids changes with their concentration. The flash point is related to the molecular composition of the oil and the pressure above its surface; higher pressure results in a higher flash point. The flash point is an important indicator for preventing oil fires. In open containers, the heating temperature of the oil should be 10°C below its flash point; there is no such restriction when heating in pressurized containers. The lowest temperature at which a mixture of gases evaporated from the surface of a flammable liquid and air can ignite in the presence of an open flame, resulting in continuous combustion lasting no less than 5 seconds, is called the ignition point. The ignition point is higher than the flash point. From a fire prevention perspective, it is desirable for the oil to have a high flash point and ignition point, with a large difference between the two. From a combustion perspective, it is desirable to have a low flash point and ignition point, with the difference between the two also being as small as possible.
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion). At the flash point temperature, only the mixture of vapor and air from the liquid can burn; the liquid itself cannot burn. This is because at the flash point temperature, the liquid evaporates slowly. During a flash fire, the vapor mixture burns up quickly, and the liquid does not have enough time to evaporate the necessary combustible vapor to continue feeding the combustion; as a result, the flash fire stops. Although the flash fire stopped, it is sufficient to indicate a risk of fire. Therefore, the flash point is the main indicator for measuring the fire hazard of oils. For homologous flammable liquids, there is a certain pattern in the variation of their flash points; specifically, for liquid flash points: (1) they increase as the molecular weight increases ； (2) Increases as the specific gravity increases ； (3) Increases as the boiling point rises ； (4) It increases as the vapor pressure decreases. For liquid mixtures, the flash point variation also exhibits the following characteristics: (1) The flash point of a two-liquid mixture is generally lower than the average of the flash points of these two flammable liquids. For example, the flash point of gasoline for use in vehicles is -36 degrees, while that of kerosene for use in lamps is 45 degrees. If gasoline and kerosene are mixed in a 1:1 ratio, then the flash point of the mixture should be below 4.5 degrees. This shows that in liquids with a high flash point, even the addition of a small amount of a liquid with a low flash point will lower the flash point of the liquid with the high flash point, thereby increasing its fire hazard. (2) Mixing an inert liquid into a flammable liquid can raise its flash point. For example, in a mixture of methanol and carbon tetrachloride containing 41% carbon tetrachloride, no flash ignition occurs even when exposed to an open flame. (3) The flash point of water-soluble flammable liquids (methanol, ethanol, propanol, etc.) increases as the water content rises.
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion). At the flash point temperature, only the mixture of vapor and air from the liquid can burn; the liquid itself cannot burn. This is because at the flash point temperature, the liquid evaporates slowly. During a flash fire, the vapor mixture burns up quickly, and the liquid does not have enough time to evaporate the necessary combustible vapor to continue feeding the combustion; as a result, the flash fire stops. Although the flash fire stopped, it is sufficient to indicate a risk of fire. Therefore, the flash point is the main indicator for measuring the fire hazard of oils. For homologous flammable liquids, there is a certain pattern in the variation of their flash points; specifically, for liquid flash points: (1) they increase as the molecular weight increases ； (2) Increases as the specific gravity increases ； (3) Increases as the boiling point rises ； (4) It increases as the vapor pressure decreases. For liquid mixtures, the flash point variation also exhibits the following characteristics: (1) The flash point of a two-liquid mixture is generally lower than the average of the flash points of these two flammable liquids. For example, the flash point of gasoline for use in vehicles is -36 degrees, while that of kerosene for use in lamps is 45 degrees. If gasoline and kerosene are mixed in a 1:1 ratio, then the flash point of the mixture should be below 4.5 degrees. This shows that in liquids with a high flash point, even the addition of a small amount of a liquid with a low flash point will lower the flash point of the liquid with the high flash point, thereby increasing its fire hazard. (2) Mixing an inert liquid into a flammable liquid can raise its flash point. For example, in a mixture of methanol and carbon tetrachloride containing 41% carbon tetrachloride, no flash ignition occurs even when exposed to an open flame. (3) The flash point of water-soluble flammable liquids (methanol, ethanol, propanol, etc.) increases as the water content rises.
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion).
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion). At the flash point temperature, only the mixture of vapor and air from the liquid can burn; the liquid itself cannot burn. This is because at the flash point temperature, the liquid evaporates slowly. During a flash fire, the vapor mixture burns up quickly, and the liquid does not have enough time to evaporate the necessary combustible vapor to continue feeding the combustion; as a result, the flash fire stops. Although the flash fire stopped, it is sufficient to indicate a risk of fire. Therefore, the flash point is the main indicator for measuring the fire hazard of oils. For homologous flammable liquids, there is a certain pattern in the variation of their flash points; specifically, for liquid flash points: (1) they increase as the molecular weight increases ； (2) Increases as the specific gravity increases ； (3) Increases as the boiling point rises ； (4) It increases as the vapor pressure decreases. For liquid mixtures, the flash point variation also exhibits the following characteristics: (1) The flash point of a two-liquid mixture is generally lower than the average of the flash points of these two flammable liquids. For example, the flash point of gasoline for use in vehicles is -36 degrees, while that of kerosene for use in lamps is 45 degrees. If gasoline and kerosene are mixed in a 1:1 ratio, then the flash point of the mixture should be below 4.5 degrees. This shows that in liquids with a high flash point, even the addition of a small amount of a liquid with a low flash point will lower the flash point of the liquid with the high flash point, thereby increasing its fire hazard. (2) Mixing an inert liquid into a flammable liquid can raise its flash point. For example, in a mixture of methanol and carbon tetrachloride containing 41% carbon tetrachloride, no flash ignition occurs even when exposed to an open flame. (3) The flash point of water-soluble flammable liquids (methanol, ethanol, propanol, etc.) increases as the water content rises.
The flash point is the lowest temperature at which a liquid will ignite when vaporized by an ignition source under specified test conditions. Flash ignition occurs when sufficient vapor is generated on the surface of a liquid and mixes with air to form a flammable gas; upon encountering a source of fire, this results in a brief flash of light that disappears immediately. The lowest temperature at which flash ignition occurs is called the flash point. The flash point depends on the density of the flammable liquid, the air pressure at the liquid surface, as well as whether light components are present in the flammable liquid and their concentration.
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion). At the flash point temperature, only the mixture of vapor and air from the liquid can burn; the liquid itself cannot burn. This is because at the flash point temperature, the liquid evaporates slowly. During a flash fire, the vapor mixture burns up quickly, and the liquid does not have enough time to evaporate the necessary combustible vapor to continue feeding the combustion; as a result, the flash fire stops. Although the flash fire stopped, it is sufficient to indicate a risk of fire. Therefore, the flash point is the main indicator for measuring the fire hazard of oils. For homologous flammable liquids, there is a certain pattern in the variation of their flash points; specifically, for liquid flash points: (1) they increase as the molecular weight increases ； (2) Increases as the specific gravity increases ； (3) Increases as the boiling point rises ； (4) It increases as the vapor pressure decreases. For liquid mixtures, the flash point variation also exhibits the following characteristics: (1) The flash point of a two-liquid mixture is generally lower than the average of the flash points of these two flammable liquids. For example, the flash point of gasoline for use in vehicles is -36 degrees, while that of kerosene for use in lamps is 45 degrees. If gasoline and kerosene are mixed in a 1:1 ratio, then the flash point of the mixture should be below 4.5 degrees. This shows that in liquids with a high flash point, even the addition of a small amount of a liquid with a low flash point will lower the flash point of the liquid with the high flash point, thereby increasing its fire hazard. (2) Mixing an inert liquid into a flammable liquid can raise its flash point. For example, in a mixture of methanol and carbon tetrachloride containing 41% carbon tetrachloride, no flash ignition occurs even when exposed to an open flame. (3) The flash point of water-soluble flammable liquids (methanol, ethanol, propanol, etc.) increases as the water content rises.
The lowest temperature at which a liquid will flash under specified conditions. Factors affecting it: Temperature, Pressure
There is an open flash point and a closed flash point. Typically, the open flash point refers to the temperature at which the vapor emitted by a liquid can be ignited. Factors affecting it: the properties of the substance itself
The flash point is the lowest temperature at which a flammable substance will ignite (experience instantaneous combustion). At the flash point temperature, only the mixture of vapor and air from the liquid can burn; the liquid itself cannot burn. This is because at the flash point temperature, the liquid evaporates slowly. During a flash fire, the vapor mixture burns up quickly, and the liquid does not have enough time to evaporate the necessary combustible vapor to continue feeding the combustion; as a result, the flash fire stops. Although the flash fire stopped, it is sufficient to indicate a risk of fire. Therefore, the flash point is the main indicator for measuring the fire hazard of oils. For homologous flammable liquids, there is a certain pattern in the variation of their flash points; specifically, for liquid flash points: (1) they increase as the molecular weight increases ； (2) Increases as the specific gravity increases ； (3) Increases as the boiling point rises ； (4) It increases as the vapor pressure decreases. For liquid mixtures, the flash point variation also exhibits the following characteristics: (1) The flash point of a two-liquid mixture is generally lower than the average of the flash points of these two flammable liquids. For example, the flash point of gasoline for use in vehicles is -36 degrees, while that of kerosene for use in lamps is 45 degrees. If gasoline and kerosene are mixed in a 1:1 ratio, then the flash point of the mixture should be below 4.5 degrees. This shows that in liquids with a high flash point, even the addition of a small amount of a liquid with a low flash point will lower the flash point of the liquid with the high flash point, thereby increasing its fire hazard. (2) Mixing an inert liquid into a flammable liquid can raise its flash point. For example, in a mixture of methanol and carbon tetrachloride containing 41% carbon tetrachloride, no flash ignition occurs even when exposed to an open flame. (3) The flash point of water-soluble flammable liquids (methanol, ethanol, propanol, etc.) increases as the water content rises.
Flash point: It is the lowest temperature at which a liquid will ignite when vaporized by an ignition source under specified test conditions. Flash ignition occurs when sufficient vapor is generated on the surface of a liquid and mixes with air to form a flammable gas; upon encountering a source of fire, this results in a brief flash of light that disappears immediately. The lowest temperature at which flash ignition occurs is called the flash point. The flash point depends on the density of the flammable liquid, the air pressure at the liquid surface, as well as whether light components are present in the flammable liquid and their concentration. If the flash point of flammable liquids suddenly decreases during use, incidents such as the mixing of light oils or hydrolysis (in the case of certain synthetic oils) may occur, and this requires attention ； The flash point of flammable liquids changes with their concentration ； The flash point is related to the molecular composition of the oil and the pressure above its surface; higher pressure results in a higher flash point.