File Name: flash and fire point of diesel .zip
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And, that in a nutshell is why flammability testing is important. In order to minimize the risk of fire or explosion, it is important to evaluate the flammability characteristics of the material to understand key characteristics such as the lower flammability limit, upper flammability limit, limiting oxygen concentration and deflagration index. Simply put, these are defined as:. A variety of different flammability tests can be performed to allow for determination of these characteristics, and the understanding of these conditions is essential when implementing proper safety practices. When conducting flammability testing, it is important that customers communicate what data is being sought so that testing can be properly designed in order to determine the necessary flammability property of a chemical mixture.
And, because of its low cost, simplicity and versatility, the test is popular among the used oil analysis community as well. The flash point is the lowest temperature at which the vapor above the oil sample will momentarily ignite or flash when an ignition source is passed over it. The flash point typically degrees C or degrees F for mineral oils is an indication of the safety hazards of a lubricant with respect to fire and explosion.
However, the flash point should not be confused with the auto ignition temperature AIT , which is the temperature typically degrees C or to degrees F for mineral oils at which the oil vapor will combust spontaneously without an ignition source. This is an important property of fire-resistant hydraulic fluids in EHC systems on steam turbines.
According to ASTM, which first standardized the test in , the flash point is the lowest temperature at which an ignition source causes the vapors of the specimen lubricant to ignite under specified conditions.
The oil flashes because a flammable mixture results when it is heated sufficiently, causing vapors to emerge and mix with oxygen in the air. The flash point temperature of an oil corresponds roughly to a vapor pressure of mm Hg.
As the name implies, the fire point is the temperature at which a sustained flame results longer than four seconds. Originally, the flash point was developed for the purpose of determining the fire hazard of fuels and oils being stored or transported. However, combined with other tests such as viscosity, viscosity index , and specific gravity, the flash point can help reveal both the quality of the crude oil from which the lubricant was derived and the quality of the refining process.
The flash point can also identify whether the base oil was a wide or narrow single cut or whether it represents a blend of two fractions two base oils of different viscosities mixed together. And, the flash point may give some indication about the volatility and content of the most volatile components of the test oil.
The flash point tells nothing, however, about the volatility of the oil as a whole. Unlike mineral oils that start to evaporate long before their flash points are reached, some synthetics do not evaporate until they begin to decompose destructive distillation. Hence, the flash points of these synthetics can range much higher than those of mineral oils of conventionally refined similar viscosities. While there are more precise methods for measuring fuel dilution e.
Because of the low flash points of most fuels, a sudden drop in flash temperature in a crankcase oil can usually be relied upon as an indication of dilution. However, there are exceptions, particularly in the case of diesel fuel. Because there is often some overlap of the light-end volatile constituents of some lube oils with the heavy ends of the fuel, the presence of fuel dilution may be less distinct.
This is particularly true when all of the fuel dilution is the result of blow-by, i. In such cases only the heavy ends may enter the oil with the oxidized light ends as a part of the exhaust gases.
However, in the case of leakage of raw fuel, including dribbling injectors, all or a high percentage of the fuel light-ends can be blended with the crankcase oil.
Another influencing factor is that hot running crankcase temperatures alone are often sufficient to boil off light-end fuel fractions, leaving the less volatile and more viscous heavy-ends mixed with the oil and potentially undetectable with the flash point test. Fuel dilution reduces viscosity of a lubricant. However, if viscometry was used alone to screen for fuel, it is possible that little to no thinning could be detected for the reasons described above.
This is further compounded by the often interfering effects of viscous thickening from soot also a product of blow-by , base oil volatility thickening , and VI improver shear thinning. It is possible that a crankcase oil could be thinning from fuel dilution or not if the light ends boil away , thinning from VI improver sheardown, thickening from volatilization, and thickening from rising soot load - all at the same time.
However, despite the neutral viscosity effect, potential destructive consequences, including loss of dispersancy , antiwear protection, and oxidation stability , represent a serious risk. Flash point can enhance the ability of an oil analysis program to reliably identify abnormal levels of fuel. Even when used only as an exception test, it can guard against a false positive conclusion on fuel dilution from an original low viscosity result.
If, for example, the low viscosity was caused by improper makeup oil of lower viscosity , the flash may confirm this by indicating no change from the new oil baseline. Fuel dilution, however, would almost certainly register a lower flash point from the reference new oil. Figure 3 shows a graph that presents the general relationship between flash point and percent dilution raw fuel. The small quantity of oil used 2 ml enables the target temperature to be reached quickly, typically within minutes.
The ignitor is then applied to initiate the flash. If a flash is obtained the test fails the oil, suggesting the possibility of fuel dilution. In the case when an oil fails the flash point screening test, one or more exception tests could then be prescribed to both confirm and quantify the fuel dilution. Possible exception tests include gas chromatography and infrared spectroscopy.
So too, determining the finite flash point temperature can be deployed to estimate percent fuel dilution Figure 3. Depending on application, for diesel engines, a cautionary limit is typically set at around 1. Application-specific calibration curves based on the actual test protocol open cup, closed cup, etc. Besides viscosity and flash, other routine oil analysis tests that might reveal fuel dilution include elemental analysis proportionally reduced additive concentrations , blotter spot test , crackle test , odor, and oxidation stability e.
It has also been reported that viscosity index will change sharply due to fuel dilution. Diesel fuel concentrations in excess of five percent have been found to cause premature loss of dispersancy, leading to deposits and filter plugging.
This might be observed from the blotter spot test or by defining the a ratio of coagulated pentane insolubles to uncoagulated pentane insolubles ASTM D , sometimes called the dispersion index.
A low index number suggests poor dispersancy. It is not common for labs to employ flash point testing in applications outside of used engine oil analysis. However, depending on the machine application, operating environment, potential for contamination, and stressing conditions, a flash point test may provide the earliest indication of certain failure and root cause conditions.
Therefore its use should be considered in defining routine test slates for all used oil analysis programs. And, it definitely should be among several strategic exception tests used to confirm and diagnose occasional non-conforming conditions flagged by routine tests such as viscosity and infrared spectroscopy. Below is a list of applications for flash point testing other than fuel dilution :.
Occasionally, very high, localized temperatures can lead to cleavage and gas evolution within the oil, lowering the flash point. This might occur from the high flash temperatures not to be confused with flash point of highly loaded squeeze films in the rolling contacts of certain bearings and gear units. It can also occur where machine surface temperatures are extremely hot due to close proximity to steam or furnaces. The mis-application of high watt-density tank heaters can also cause thermal cracking.
And, aeration of hydraulic systems commonly subject the fluid to extremely high adiabatic temperatures when air bubbles are suddenly pressurized it can also occur in compressors and load zones of bearings.
In hydraulic systems, the condition is referred to as micro-dieseling when the temperatures within the compressed air bubbles are high enough to auto-ignite.
The cracking can lead to the formation of carbon fines coke and low boiling-point volatiles within the oil that reduce the flash point temperature. Also, exposure to Gamma radiation, such as in the case of fuel handling hydraulics in a nuclear power plant, can cause gas evolution and lower flash point. Because the flash point is sensitive to low-boiling point constituents within the oil a change in flash point up or down might indicate the presence of an uninvited guest, i.
Besides diesel and gasoline fuel, other common low-boiling point contaminants include natural gas gas engines and compressors and solvents. Solvent contamination might be found when, for instance, a gearbox is cleaned out with naphtha, kerosene, or other flammable cleaner.
Certain contaminants are known to actually raise the flash point. This can occur from a high level of water contamination in the oil, a common interference in flash point testing. Water contamination can also give a false low flash, particularly in certain mini-flash systems that use change in pressure to detect flash. The boiling off of the water can give a false positive on fuel for instance.
Water can also snuff out the flame in cases where a gas pilot flame is used. One solution to dealing with water is to add particles of calcium sulfates or calcium carbonate prior to performing the flash. Centrifuging is yet another solution. It has also been reported that coal dust and glycol antifreeze can synthesize volatile oil components resulting in an up-tick in flash point.
Flash points also vary somewhat within viscosity grades as influenced by the crude oil type and refining process. As previously mentioned, synthetic lubricants typically exhibit higher flash points than their mineral-oil counterparts. Therefore, it is sometimes possible to detect a wrong or mixed oil with the use of flash point testing. However, from a practical standpoint, other routine tests such as infrared spectroscopy, TAN, viscosity and color are more effective in alerting users to wrong or mixed lubricants.
In these instances, the flash point test better serves in a confirming role. A lubricant subjected to high operating temperatures over a long period of time might lose a considerable portion of its light ends from evaporation. Additionally, it is possible that the routine use of vacuum dehydrators at high inlet temperatures can cause evaporation of certain additives and low-boiling point base oil fractions.
In order to insure accurate flash point results it is important that a representative sample be presented to the instrument. For various reasons, this is easier said than done. It is worth noting that the precautions here are equally true for any test FTIR , gas chromatography, etc. Many fuels, for instance, will evaporate from the oil over time if the sample is not properly sealed.
And, light fuel fractions can literally diffuse through the walls of certain sample containers such as those made of polyethylene and polypropylene. In such cases, PET plastic and glass bottles are preferred.
There may also be loss of light fuel fractions when vacuum sampling pumps are used to pull hot engine oils from crankcases. The vacuum generated not only draws the oil but can sharply reduce the boiling point of the fuel, leading to its evaporation.
For this and other important reasons, the preferred sampling location for crankcase oils is on the pressure line between the pump and the filter using an acceptable live-zone sampling procedure.
Caution needs to be taken by the laboratory as well. Samples should not be left uncapped, subjected to vacuum, or heated prior to flash point testing or any test for fuel dilution.
There are many detailed procedures and guidelines included in the ASTM flash point standards that should be observed to insure quality and test accuracy. In order to insure accuracy and quality it is best to follow standardized flash point procedures and instrument configurations.
However, only three are commonly used for lubricants and hydraulic fluids. And, because of the differences in these procedures, a flash point temperature must be always quoted specific to the procedure employed. A brief description of the three flash point procedures follows see also Figure 6 :. This test procedure utilizes an open metal container that is filled with the sample oil. The oil is then heated at a prescribed rate and periodically a small pilot flame ignitor is passed over its surface.
This continues until a flash appears. The oil temperature is then recorded as its flash point. In the used oil analysis lab however, the procedure can require more oil than typically available and an exceedingly long test time.
Historical Version s - view previous versions of standard. Work Item s - proposed revisions of this standard. More D It is only one of a number of properties which must be considered in assessing the overall flammability hazard of a material. One should consult the particular regulation involved for precise definitions of these classifications. However, results of these test methods may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use. The precision of in-use lubricating oils has not been determined.
with an open flame. The lowest temperature at which the vapor will ignite is the fuel's flash point. Diesel fuel. #2 as specified by ASTM D has a minimum flash.
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Autoignition Temperature Defined The lowest temperature at which a heated liquid's vapors in air will selfignite and burn, without exposure to any ignition source. Flash Point and Fire Point Testing The liquid to be tested is heated in a cup and the rising liquid temperature is continuously measured. A small flame is mechanically passed back and forth just above the surface of the liquid. The ignitions repeat as the liquid temperature continues to rise. The observed temperature when the burning becomes continuous is the Fire Point.
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Flash and fire point in engine perspective Gasoline has a flash point around ⁰ C whereas diesel has flash points higher than 52⁰ C. Lower flash points are the indicators of good flammability and volatility.Adam F. 14.05.2021 at 07:50
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