Experiment # 6
FLASH & FIRE POINT TEST FOR ASPHALT BY CLEVELAND OPEN CUP
RELATED THEORY Fire Point
Flash point is the lowest temperature corrected to a barometric pressure of 101.3 kPa (760 mm Hg), at which application of a test flame causes the vapor of a specimen to ignite under specified conditions of test.The material is deemed to have flashed when a large flame appears and instantaneously propagates itself over the surface of the specimen.
Note: Occasionally, particularly near the actual flash point, the application of test flame will cause the blue halo or an enlarged flame; this is not a flash and should be ignored.
FIRE POINT Fire Point
It is the lowest temperature at which a specimen will sustain burning for 5 seconds. A flammable material is the one, which form flames, but does not sustain fire while a combustible material is the one, which sustains fire/burning.
SOURCES OF BITUMEN
Bitumen is generally obtained from the following three sources;
- Naturally occurring (in West Indies).
- Extracted from Limestone and Sandstone (procedure adopted in USA).
- From Oil Refineries (this is the major source of bitumen in Pakistan).
ASPHALT CEMENT (AC)
Asphalt Cement shall be oil asphalt or a mixture of refined liquid asphalt and refined solid asphalt, prepared from crude asphaltic petroleum. It shall be free from admixture with any residues obtained by the artificial distillation of coal, coal tar or paraffin and shall be homogeneous and free from water. Fire Point
|Temperature Condition||* Asphalt Grade|
|Cold, mean annual air temperature < 7 °C (45 °F)||AC-10|
|80 / 100 pen|
|Warm, mean annual air temperature between 7 °C (45 °F) and 24 °C (75 °F)||AC-20|
|60 / 70 pen|
|Hot, mean annual air temperature > 24 °C (75 °F)||AC-40|
|40 / 50 pen|
SCOPE & SIGNIFICANCE Fire Point
- Flash point measures the tendency of the sample to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that must be considered in assessing the overall flammability hazard of a material.
- Flash point is used in shipping and safety regulations to differentiate between ‘‘flammable’’ and ‘‘combustible’’ materials.
- Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively nonvolatile or nonflammable material.
- Fire point measures the characteristics of the sample to support combustion.
- Bituminous materials give rise to volatiles at high temperature, as they are basically the hydrocarbons. These volatiles catch fire causing a flash, which is very hazardous.
- During construction of bituminous pavements, the engineer may restrict the mixing or application temperatures well within the limits. The test therefore gives indication of critical temperature at and above which suitable precautions should be taken to eliminate fire hazards during use of asphalts. In other words heating should be limited to a temperature well below the flash point.
APPARATUS Fire Point
1. Cleveland Cup Apparatus: It consists of test cup, heating plate, test flame applicator, heater, thermometer support and heating plate support, all conforming to the following requirements.
- Test Cup — It is made of brass. The cup may be equipped with a handle.
- Heating Plate — A brass, cast iron, wrought iron, or steel plate with a center hole surrounded by an area of plane depression, and a sheet of hard asbestos board which covers the metal plate except over the area of plane depression in which the test cup is supported. The metal plate may be square instead of round and have suitable extension for mounting the test flame applicator device and the thermometer support. The metal bead is mounted on the plate so that it extends through and slightly above a small hole in the asbestos board. Fire Point
- Test Flame Applicator — The device for applying the test flame may be of any suitable design, but the tip shall be 1.6 to 5.0 mm in diameter at the end and the orifice shall have an approximate diameter of 0.8 mm. The device for applying the test flame shall be so mounted to permit automatic duplication of the sweep of the test flame, the radius of swing being not less than 150 mm and the center of the orifice moving’ in a plane not more than 2.5 mm above the cup. A bead having a diameter of 3.8 to 5.4 mm may be mounted in a convenient position on the apparatus so the size of the test flame can be compared to it. Fire Point
- Heater — Heat may be supplied from any convenient source. The use of a gas burner or alcohol lamp is permitted, but under no circumstances are products of combustion or free flame to be allowed to come up around the cup. An electric heater controlled by a variable voltage transformer is preferred. The source of heat shall be centered under the opening of the heating plate with no local superheating.
- Thermometer Support — A device which will hold the thermometer in the specified position during a test and permits easy removal of the thermometer from the test cup upon completion of a test.
- Heating Plate Support — Any convenient support which will hold the heating plate level and steady may be employed. Fire Point
2. Shield: A shield having an area of 460mm2 and 610mm high and having an open front is used.
3. Thermometer: A thermometer having the required range. Fire Point
Preparation of Apparatus
Support the apparatus on a level table. Shield the top of the apparatus from strong intensity of light by any suitable means to permit ready detection of the flash point. Fire Point
Wash the test cup with an appropriate solvent to remove any oil or traces of gum or residue remaining from a previous test. If any deposits of carbon are present, they should be removed with steel wool. Flush the cup with cold water and dry for a few minutes over an open flame, on a hot plate, or in an oven to remove the last traces of solvent and water. Cool the cup to at least 56 °C below the expected flash point before using.
Support the thermometer in a vertical position with the bottom of the bulb 6.4 mm from the bottom of the cup and located at a point halfway between the center and side of the cup on the diameter perpendicular to the line of the sweep of the test flame and on the side opposite to the test flame burner arm. Fire Point
- Fill the cup; at any convenient temperature not exceeding 100 °C or above the softening point; so that the top of the meniscus is at the filling line.
- Remove the excess sample using a pipette or other suitable device; however, if there is sample on the outside of the apparatus, empty, clean, and refill it. Destroy any air bubbles on the surface of the sample.
- Lit the test flame and adjust it to a diameter of 3.8 to 5.4 mm.
- Apply heat initially so that the rate of temperature rise of the sample is 14 to 17 °C per minute. When the sample temperature is approximately 56 °C below the anticipated flash point, decrease the heat so that the rate of temperature rise for 28°C before the flash point is 5 to 6°C per minute.
- Starting at least 28 °C below the flash point, apply the test flame when the temperature read on the thermometer reaches each successive 2 °C mark. Pass the test flame across the center of the cup, at right angles to the diameter, which passes through the thermometer. With a smooth, continuous motion apply the flame either in a straight line or along the circumference of a circle having a radius of at least 150 mm. The center of the test flame must move in a plane not more than 2.5 mm above the plane of the upper edge of the cup passing in one direction first, then in the opposite direction the next lime. The time consumed in passing the test flame across the cup shall be about one second (1 s.). During the last 17 °C rise in temperature prior to the flash point, care must be taken to avoid disturbing the vapors in the test cup by careless movements or bathing near the cup.
- Record as the observed flash point the temperature read on the thermometer when a flash appears at any point on the surface of the material, but does not confuse the true flash with the bluish halo that sometimes surrounds the test flame.
- To determine the fire point, continue heating so that the sample temperature increases at a rate of 5 to 6 °C. Continue the application of the test flame at 2°C intervals until the oil ignites and continues to burn for at least 5 second. Record the temperature at the point as the fire point of the oil.
- Do not breathe close to the apparatus as the fumes are injurious to health.
- Turn the fans off so that the fumes can be accumulated over the cup.
- Tip of the thermometer should not touch the bottom or sides of the cup.
- The operator must exercise and take appropriate safety precautions during the initial application of the test flame, since samples containing low flash material may give an abnormally strong flash when the test flame is first applied.
CALCULATIONS AND REPORT
Observe and record the barometric pressure at the time of the test. When the pressure differs from 760 mm Hg, correct the flash or fire point, or both, by means of the following equations:
Corrected flash or fire point, or both = C + 0.03 (760 — P)
C = observed flash or fire point, or both, to the nearest 2 °C, and
P = Barometric pressure, mm Hg.
Record the corrected flash or fire joint value, or both, to the nearest 5 °C or 2°C.
FLASH POINT OF DIFFERENT GRADES OF ASPHALT:
|Property||AC – 2.5||AC – 5||AC – 10||AC – 20||AC – 40|
|Flash Point COC, °C min.||163||177||219||232||232|
Note: AC – 10 is most commonly used in Pakistan.
OBSERVATIONS & RESULTS
|Time (minutes)||Temperature (°C)||Remarks|
The Experiment has been performed successfully and the results which we have got are showing that the flash point of the bitumen sample came out to be at 308◦ and time corresponding to this temperature was 9.12 minutes. Whereas the fire point was found out to be at temperature of 352◦ and the time corresponding to this temperature was 24.25 minutes. The trend line of the graph is showing the relationship between temperature and time.
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