What Does Fire Point Mean?
Fire point refers to the temperature at or above which a flammable liquid produces enough vapor to ignite by spark or flame and burn for at least five seconds. The fire point is usually 10°C more than the flash point of a liquid.
The fire point of a substance differs from the flash point in that it is a lower temperature and ignites briefly, but cannot sustain the fire. At the flash point, the combustion sieges immediately when the flame or external ignition source is removed. At the fire point, the combustion sustains at least for 5 seconds after the flame is removed. The flash point is significantly lower than the fire point by usually 8 to 10 percent. The flash point and fire point should not be confused with the auto-ignition temperature of a liquid, which is the temperature at which the liquid ignites spontaneously without any external ignition source such as a flame or a spark.
Flash and fire point
The open cub Cleveland apparatus is used to find the biodiesel and diesel flash and fire points. The experiment is conducted according to the ASTM D93 standard. Flash point is the temperature at which the ignition source will ignite the testing sample. The flash point is determined by heating the sample of fuel in a container and passing the flame over the surface of the sample. If the temperature is at or above the flash point, the vapor will ignite and an easily detectable flash can be observed. The flash produced need not sustain for long time. Whereas, fire point is the minimum temperature at which vapor of the fuel steadily burns at least for five seconds once ignited. Flash point and fire point are the property that directly signifies whether the fuel is safely transportable; it is not related to engine performance.
Flash and fire point
The flashpoint for any volatile material is defined as the lowest temperature at which vapors of the material will ignite when ignited by a source. Similarly, the fire point is defined as the lowest temperature at which vapors of the material will catch fire and continue burning even after the ignition source is removed. The fire point is higher than the flash point because the vapors produced at the flash point are not sufficient enough to ignite the fuel. Flash and fire points depend upon the volatility of the biodiesel. Volatility is the tendency of the substance to vaporize, and it is directly related to the vapor pressure of the biodiesel at that particular temperature. The biodiesel exhibiting higher vapor pressure at a given temperature is said to be more volatile than the one exhibiting lower vapor pressure at the same temperature. Hence the lower the NBP (normal boiling point), the higher the volatility, which is in turn inversely proportional to its flash and fire point.
The flash and fire point of AMC biodiesel was found to be 164°C and 175°C, respectively. The flash point of Karanja biodiesel was found to be 97.8°C. The flash point of Jatropha biodiesel was found to be 192°C. The reason for the close flash point values of AMC biodiesel and Jatropha biodiesel is their identical average molecular masses. Also, the length of the fatty acid chains is directly proportional to their boiling points, and branching is directly proportional to their melting points. Weight percentage of long chain fatty acids is greater for Jatropha compared to AMC, even though they have identical average molecular masses. Therefore, the NBP of Jatropha is more compared to AMC, owing to its higher flash and fire points. Karanja biodiesel’s average molecular mass is quite low compared to these two, and hence the NBT is quite low and very volatile. The source temperature will always be higher than either the flash or fire point, and both these parameters are independent of ignition temperature. The flashpoint of fossil diesel is always less than that of biodiesel, and hence it cannot be safely stored.
The accumulation of historical wildfires events into a geospatial database would be essential for wildfire sensitivity mapping and validating model performance. Two types of satellite data were employed to acquire the fire point information in this investigation between the year (2015–20). MODIS data with a 1000-meter resolution (https://firms.modaps.eosdis.nasa.gov/) and VIIRS data with 375 resolution, which is more sensitive to detecting fires, were used to identify forest fire location points (Louis Giglio et al., 2016). Apart from these satellite images, historical fire points data of the West Bengal Forest department of Purulia district between the years (2015–20) were also used in this study. Finally, a ground-level survey was conducted between (March–April 2021) during the fire events, and reported areas were spotted with GPS points. A total of 178 wildfire locations point were spotted; and after that, all those fire points were then integrated with the wildfires inventory dataset to conduct susceptibility mapping and validations. Out of 178 wildfire locations points, 70% (124) have been used for training, and the remaining 30% (53) were used for validation of the model. Photographs of wildfires events were obtained from local inhabitants and media reports. The wildfire susceptibility maps subsequently overlay with wildfire points, and then the validity of the wildfire susceptibility maps was tested using the area under the curve (AUC) technique
The most obvious problem is that oil-base muds will burn. The flash point of a liquid hydrocarbon is the temperature to which it must be heated to emit sufficient flammable vapor to flash when brought into contact with a flame. The fire point of a hydrocarbon liquid is the higher temperature at which the oil vapors will continue to burn when ignited. In general, the open flash point is 50 to 70 degrees Fahrenheit less than the fire point.
Most oil-base muds are made with #2 diesel oil. The flash point for diesel is generally accepted to be about 140 degrees Fahrenheit. On that basis, the fire point would be about 200 degrees Fahrenheit. Mixing the oil-base mud with hydrocarbons from the reservoir will only increase the tendency to burn. The exposure of gas with the proper concentrations of air to any open flame or a source capable of raising the temperature of the air-gas mixture to about 1200 degrees Fahrenheit will result in a fire.
Most wildfire incidents in Ireland occur in spring, most notably, . Fire activity in uplands and peatlands rapidly subsides during late May and June, as fresh, live, and nonflammable vegetation states dominate.
Analysis of 1760 MODIS fire points detected between 2002 and 2017 shows that 50% of these detections occurred during April (873), with 24% occurring during May (421), and 12% during March.
A further 5.9% of detections occurred during June. The spatial distribution of the MODIS fire points (Figure 20.2.3) suggests that these may involve permitted burning of agricultural residues as opposed to wildfire incidents
This parameter is not involved in classification of chemicals by risk of ignition as is flash point involved.
Rather, autoignition temperature (AIT) is involved in classification of how chemicals are used to minimize or avoid ignition risk. This is especially significant in cold cleaning.
3.7.1 Definition of AIT
The AIT of a chemical is the lowest temperature at which the chemical72 will spontaneously ignite in the absence of an external ignition source, such as a spark or flame.
For a value of AIT to be a valid measurement, ignition must be initiated without external source of energy AND sustained without external source of energy.
3.7.2 Heat Transfer Rules
The general definition of an ignition source in Section 3.3.1 includes both external sources of energy(sparks or static electricity), and hot surfaces. All can produce a self-sustaining oxidation reaction between the Carbon and Hydrogen atoms in the chemical, and Oxygen atoms in the air.
As much as availability for reaction of Carbon and Hydrogen atoms in the chemical molecule is significant in controlling ignition, more so is heat transfer within the vapor mixture as well as between the vapor mixture and it surroundings.
A reaction can’t be sustained if only a portion of the reactants is at a temperature below that necessary to sustain reaction.73
Most commonly, measurements of AIT are made in an apparatus similar to a closed-cup flash point tester using a procedure specified by the ASTM Method E659.
Differences between AIT and flash/fire points74 are shown in Table
A confluence of flammable, mature, fine fuel vegetation and dry weather makes fires on Irish peatlands possible. In spring, most upland vegetation is in a mature state and capable of rapid drying when weather conditions permit. However, under normal early spring conditions, only surface vegetation is capable of sustaining combustion and litter and soil layers remain moist. Should prolonged drought conditions exist during or immediately following the mature phase of vegetation, it is possible for fire to transfer the heat from surface vegetation to dry litter and organic soil of subsurface layers below, deriving to peat fires. The smoldering combustion in organic soils can last for weeks and ignite new vegetation fires if drought conditions prevail.
An indication of multi annual cyclical fire incidence is provided by Irish Fire and Rescue Service data between 2000 and 2015 (Figure 20.2.4). Peaks and troughs are in line with prevailing spring weather for given years
Fire Point Definition
Fire point is the lowest temperature where the vapor of a liquid will initiate and sustain a combustion reaction. By definition, the fuel must continue to burn for at least 5 seconds following ignition by an open flame for the temperature to be considered the fire point.
Fire Point vs Flash Point
Contrast this with the flash point, which is a lower temperature at which a substance will ignite, but may not continue to burn.
The fire point for a specific fuel is not typically listed, while flash point tables are readily available. Generally, the fire point is about 10 °C higher than the flash point, but if the value must be known, it should be determined experimentally.