GB/T 2430-1981 Jet fuel freezing point determination method GB/T2430-1981 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Jet fuels-Determination of freezing point
Jet fuels-Determination of freezing point This method is applicable to the determination of the freezing point of jet fuel. GB/T 2430-81
(Confirmed in 1988)
Under the determination conditions, after the sample appears crystallized, the lowest temperature at which the originally formed hydrocarbon crystals disappear is the freezing point. Note: This standard is established with reference to 1S03013-1974 "Determination of freezing point of aviation fuel". 1 Method Overview
Take 25 liters of sample and pour it into a clean and dry double-walled test tube, install a stirrer and a thermometer, put the double-walled test tube into a thermos bottle with a cooling medium, and stir the sample continuously to lower its temperature until crystals visible to the naked eye begin to appear in the sample, then remove the double-walled test tube from the refrigerant, slowly heat the sample, and stir the sample continuously until the lowest temperature at which the hydrocarbon crystals completely disappear is the freezing point.
2 Apparatus
2.1 Double-walled glass test tube (see Figure 1), the space between the inner and outer tubes is filled with dry nitrogen or air at normal pressure. The tube mouth is tightly plugged with a cork, the thermometer and the gland are inserted into the cork, and the stirrer passes through the gland. 2.2 Gland: During low temperature testing, in order to prevent moisture in the air from condensing in the sample tube, the gland as shown in Figure 2 must be installed. The gland is tightly inserted into the cork, and the space between the brass tube and the stirrer is filled with absorbent cotton (a moisture-proof tube as shown in Figure 3 or Figure 4 can also be used). 2.3 Moisture-proof tube: as shown in Figures 3 and 4. These two tubes can also be used instead of the gland to prevent moisture condensation. 2.4 Stirrer: It is a brass rod with a diameter of about 1.6 mm, which is smoothly bent into three turns of spiral at the lower end. 2.5 Wide-mouth thermos flask without mercury coating (see Figure 1): Its volume should be sufficient to accommodate the required volume of coolant and enable the double-walled test tube to be immersed to the specified depth.
2.6 Thermometer: Full diffuse type, in accordance with the following specifications. Temperature range
80 ~ + 20℃
Full immersion depth;
Minimum graduation 0.5℃,
1 and 5℃;
Each longer scale line
Digits every 5℃,
Scale error does not exceed 1℃,
Expansion chamber is allowed to be heated to 45℃;
Total length 300±10mm,wwW.bzxz.Net
Rod diameter 5.5~8.0mm,
Ball length
|Ball diameter
Ball shape
8～16 meters;
not larger than the rod,
cylindrical,
the length of the scale part
170～210 mm;
the distance from the top of the ball to the 0℃ scale line is 220 mm at most, and the top is added with "
flat or ring-shaped.
The State Administration of Standardization promulgated on February 13, 1981
implemented on July 1, 1981
GB/F2430
Note: (I) Aluminum case dyed with red durable dye or other suitable liquid should be used as the expansion liquid. The filling material above the liquid should be gas under repulsion.② At 0 r - 40, - 60 ℃
When checking the accuracy of the thermometer at -75℃, the correction value should be added to the test reading. Outer tube: 30 for outside and 26 for inside
Inner tube: 22 for outside, 18 for inside
70 for inside
Figure 1 Freezing point tester for aviation fuel
1-Thermometer, 2-Double pound glass test tube, 3-Vacuum thermos bottle without silver or mercury coating, 4-Refrigerant: 5-Dry ice, 6-Cork case, 7-Pressure cap, 8-Agitator 271
GB/T243081
Drilling 2.4
Drilling electric 2.4
Figure 2 Brass filling pressure cap for agitator
GB/T2430--81
Inlet of air or nitrogen
Figure 3 Type A moisture-proof tube
Note: This boron glass moisture-proof tube is inserted from the C end into a two-hole cork equipped with a thermometer, and then the stirrer is passed through the B and C holes of the tube and extends beyond A. Add this component to the freezing point tube. Before placing the freezing point tube in the cold bath, flush the moisture-proof tube with dry air or nitrogen entering from D and exiting from A. The air is effectively dried by passing through the U-shaped tubes in series, one of which is filled with anhydrous calcium sulfate or silica gel dehydrating agent and the other is filled with glass beads coated with phosphorus oxide. During the entire measurement period, air passes continuously through the moisture-proof tube in this way. It is usually more convenient to use dry nitrogen.
GB/T 2430-81
Dehydrating agent
Figure 4 Type B moisture-proof tube
Note: The lower part of the borosilicate glass moisture-proof tube is filled with anhydrous calcium sulfate or silica gel with a mesh diameter close to 1.7 mm until the upper end of BC is within 5 mm of point B. After the stirrer is installed, fill the glass wool impregnated with the same desiccant to the end A at the joint. The filled glass wool should be replaced every three or four tests.
3 Reagents
3.1 Anhydrous calcium sulfate or silica gel.
3.2 Phosphorus pentoxide: chemically pure.
3.3 Ethanol: 1% for industry.
8.4 Nitrogen.
3.5 Ice.
4 Test procedure
Pour 25 ml of the sample into a clean, dry double-walled test tube. Tightly plug the double-walled test tube with a cork with a stirrer and adjust the thermometer so that the mercury bulb is in the center of the sample. Add 1 drop of ethanol to the stirrer to wet the gland and make the stirrer move as smoothly as possible.
4.2 Clamp the double-walled test tube and place it in a thermos bottle containing a cooling medium (see Note). Add dry ice so that the coolant level in the thermos bottle is higher than the sample level during the entire test.
Note: Dry ice can be used to cool liquid (such as acetone or ethanol) as a coolant, or liquid nitrogen can be used instead of dry ice to cool the liquid, or a mechanical refrigeration device can be used. 274
GB/T2430-81
4.3 The sample should be stirred continuously during the entire test, except when observing. When stirring, be careful not to let the stirrer ring expose the fuel cut surface (see Note ①). If clouds appear at about -10℃ and the cloudiness is no longer serious when the temperature continues to drop, it is the effect of the presence of water (see Note ②), which can be ignored. When crystals visible to the naked eye begin to appear in the sample, record the temperature at which hydrocarbon crystals appear as the crystallization point. Remove the double-walled test tube from the refrigerant, slowly heat the sample, and continuously stir the sample at the same time. Record the lowest temperature at which hydrocarbon crystals completely disappear as the freezing point. If the difference between the measured crystallization point and the freezing point is greater than 3℃, repeat cooling and heating until the difference is less than 3℃. When reporting the lowest temperature at which hydrocarbon crystals completely disappear (i.e., the freezing point), add the correction value of the thermometer used (see Note ② in 2.6), and be accurate to 0.5℃ as the freezing point. Note: ① If the expected freezing point of the fuel is known, intermittent stirring is sufficient before the temperature reaches 10℃ of the expected freezing point. However, continuous stirring is required after that, and a mechanical stirring device can be used. ②) If the observation is found to hinder the crystallization of hydrocarbons, if it is due to the influence of insoluble water, the sample should be dried over anhydrous sodium sulfate before being injected into the test tube. 5 Precision
Use the following values ​​to judge the reliability of the results (95% confidence level). 5.1 Repeatability
The difference between two repeated measurements by the same operator should not exceed 0.7℃. 5.2 Reproducibility
The difference between two measurement results of the same sample proposed by two laboratories should not exceed 2.6℃. 6 Report
Take the arithmetic mean of the two repeated measurement results as the measurement result of this sample. Additional notes:
This standard was proposed by the Ministry of Petroleum Industry of the People's Republic of China. This standard was drafted by the Petrochemical Science Research Institute. 275
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