GB/T 510-2018 Determination of Freezing Point of Petroleum Products

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Card type: Test method

1. Method number / full title / English name / replacement relationship

• Standard number: GB/T 510—2018
• Chinese title: Determination of Freezing Point of Petroleum Products
• English title: Determination of solidification point for petroleum products (the original English title contains source-text extraction noise “Determination 1 of solidification point for petroleum products”, serial number “1” requires confirmation against the source standard (source-text extraction))
• Replacement relationship: replaces GB/T 510—1983 “Determination of Freezing Point of Petroleum Products”
• Previous versions: GB 510—1965, GB 510—1977, GB/T 510—1983
• Publication/implementation: published on 2018-12-28, implemented on 2019-07-01
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280)

2. Scope of application and non-applicability

• This standard specifies the method for determining the freezing point of petroleum products.
• Applicable to liquid fuels (such as diesel, biodiesel blend fuels) and lubricating oils and other petroleum products.
• In this standard, the automatic micro freezing point tester is only applicable to the determination of diesel distillate samples without additives.
• Not applicable: no other explicit exclusions are provided in the available source.

3. Method principle

Place the sample in a specified test tube, cool it to the expected temperature, tilt the test tube to 45° from the horizontal and let it stand for 1 min, observe whether the liquid surface moves, and take the highest temperature at which the liquid surface does not move as the freezing point of the sample. (See Chapter 4 Method summary)

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 5.1.1 Anhydrous ethanol: chemically pure.
• 5.1.2 Anhydrous sodium sulfate: chemically pure.
• 5.1.3 Anhydrous calcium chloride: chemically pure.

4.2 Materials

• 5.2.1 Coolant or material: industrial ethanol, dry ice or liquid nitrogen, etc., any liquid or material capable of cooling the sample to the specified test temperature. Compressor refrigeration or semiconductor refrigeration equipment may also be used.
• 5.2.2 Filter paper: qualitative filter paper.
• 5.2.3 Table salt: coarse table salt.
• 5.2.4 Absorbent cotton.

5. Instruments and equipment

5.1 Manual freezing point tester

• 6.1.1 Test tube: round-bottom, transparent glass test tube, height 160 mm±10 mm, inner diameter 20 mm±1 mm, with a ring mark on the outer wall at 30 mm from the bottom of the test tube, and a stopper capable of inserting a thermometer.
• 6.1.2 Sleeve: round-bottom glass sleeve, height 130 mm±10 mm, inner diameter 40 mm±2 mm, capable of fixing the test tube vertically in the middle of the sleeve.
• 6.1.3 Cooling bath: the temperature of the cooling bath should be controllable within ±1 ℃ of the specified temperature; the container or other suitable device for holding the coolant should have a height of not less than 160 mm, and its volume should meet the needs of use.
• 6.1.4 Thermometer or temperature measuring device: the thermometer used for sample temperature measurement shall comply with the requirements of No. GB-30, No. GB-31 or No. GB-32 in GB/T 514—2005. The thermometer used for cooling bath temperature measurement may be any type selected according to the actual use temperature. If a temperature measuring device is used, it shall be able to meet the measurement requirements specified in this standard.
• 6.1.5 Stand: used to fix the test tube, sleeve and thermometer.

5.2 Automatic micro freezing point tester (only applicable to diesel distillate samples without additives)

• 6.2.1 Sample introduction system: manual injection or automatic injection, capable of adding a certain amount of sample into the detection chamber.
• 6.2.2 Refrigeration system: provides a cold source for the detection chamber, with temperature control accuracy of ±0.1 ℃.
• 6.2.3 Detection chamber: composed of insulation layer, temperature sensor, detection chamber and other parts, with temperature measurement accuracy of 0.1 ℃.
• 6.2.4 Microcomputer: displays and controls the test process, and judges and processes the test results.

6. Recommended operating conditions

• Heating water bath temperature: 50 ℃±1 ℃ (see 8.2.3, 9.1.1).
• Cooling bath temperature: should be lower than the expected freezing point of the sample by 7 ℃~8 ℃ (see 9.1.2).
• The depth to which the sleeve and test tube assembly is immersed in the coolant shall be not less than 70 mm (see 9.1.2).
• Tilt angle: 45° from the horizontal, maintained for 1 min (see 9.1.3).
• Cooling bath temperature control: within ±1 ℃ of the specified temperature (see 6.1.3).
• Automatic micro tester temperature control accuracy: ±0.1 ℃; temperature measurement accuracy: 0.1 ℃ (see 6.2.2, 6.2.3).

7. Sampling and sample preparation

7.1 Sampling

• Unless otherwise specified, sampling shall be carried out in accordance with GB/T 4756 (see Chapter 7).

7.2 Sample preparation

• 8.1.1 Before the test begins, the sample should be shaken uniformly. An anhydrous sample may be tested directly, while a water-containing sample needs to be dehydrated. However, in product quality acceptance or arbitration testing, as long as the water content of the sample is within the range allowed by the product standard, the test may be started directly.
• 8.1.2 The sample may be dehydrated in accordance with the requirements of 8.1.3 or 8.1.4, but for samples with relatively high water content, they should first be allowed to stand, and then the clarified portion should be taken for dehydration.
• 8.1.3 For easily flowing samples, dehydration treatment is carried out by adding freshly calcined powdered anhydrous sodium sulfate or small granular anhydrous calcium chloride to the sample, then shaking and mixing the sample for 10 min~15 min, allowing it to stand, filtering with dry filter paper, and taking the clarified filtrate for testing.
• 8.1.4 For viscous samples, dehydration treatment is carried out by preheating the sample to not higher than 50 ℃, and then filtering through a table salt layer. The preparation requirements for the table salt layer are as follows: first place a metal mesh or a small amount of absorbent cotton in a funnel, and then spread freshly calcined coarse table salt crystals on it. When the sample contains much water, filtration through the table salt layers of 2~3 funnels may be required.

7.3 Preparation of the manual freezing point tester

• 8.2.1 When preparing a cooling bath containing dry ice, anhydrous ethanol may be added to a container holding coolant, filling it to 2/3 of the internal depth of the container. Then put small pieces of dry ice into the stirred anhydrous ethanol, and gradually increase the amount of dry ice according to the required degree of temperature decrease. Each time dry ice is added, attention should be paid to stirring so as not to splash or overflow the anhydrous ethanol. After the coolant no longer vigorously emits gas, add anhydrous ethanol again to reach the required height. If other refrigerants or materials are used, relevant safety precautions should be noted. When using a compressor refrigeration device, the coolant should first be injected to an appropriate position in the cooling bath.
• 8.2.2 Inject the sample into a dry, clean test tube up to the ring mark. Fix the thermometer in the center of the test tube with a stopper so that the bottom of the thermometer sensing bulb is 8 mm~10 mm from the bottom of the test tube.
• 8.2.3 Immerse the test tube containing the sample and thermometer vertically in a water bath at 50 ℃±1 ℃ and heat until the sample temperature reaches 50 ℃±1 ℃.

7.4 Preparation of the automatic micro tester

• 8.3 Prepare the instrument in accordance with the requirements of the instruction manual of the automatic micro freezing point tester.

8. Analysis procedure

8.1 Manual instrument

• 9.1.1 When the sample temperature reaches 50 ℃±1 ℃, remove the test tube containing the sample and thermometer from the water bath, wipe the outer wall of the test tube dry, and firmly install the test tube into the sleeve, ensuring that the distance between the outer wall of the test tube and the inner wall of the sleeve is equal at all points.
• 9.1.2 Fix the sleeve and test tube assembly vertically on the stand, and place it at room temperature to stand until the sample cools to 35 ℃±5 ℃, then immerse this assembly in the prepared cooling bath. The temperature of the cooling bath should be lower than the expected freezing point of the sample by 7 ℃~8 ℃. The depth to which the sleeve and test tube assembly is immersed in the coolant shall be not less than 70 mm.
• 9.1.3 When the sample temperature cools to the expected freezing point, tilt the sleeve and test tube assembly immersed in the cooling bath to 45° from the horizontal, and maintain it for 1 min; at this time, the sample therein is still required to be immersed in the coolant.
• 9.1.4 Carefully remove the sleeve and test tube assembly from the cooling bath, quickly wipe the outer wall of the sleeve with anhydrous ethanol, place it vertically, and observe through the sleeve whether there is any sign of movement of the liquid surface inside the test tube.
  • Note: When determining samples with a freezing point lower than 0 ℃, for ease of observation, 1 mL~2 mL anhydrous ethanol may be injected into the bottom of the sleeve before the test.
• 9.1.5 When the sample liquid surface position moves, remove the test tube from the sleeve, reheat the test tube until the sample reaches 50 ℃±1 ℃, then repeat the determination at a temperature 4 ℃ lower than the previous test temperature or at another lower temperature, until a test temperature at which the sample liquid surface stops moving is found.
  • Note: When the test temperature is lower than -20 ℃, before re-determination, place the test tube containing the sample and thermometer at room temperature, wait until the sample temperature rises to -20 ℃, and then immerse the test tube in a water bath for heating.
• 9.1.6 When the sample liquid surface position does not move, remove the test tube from the sleeve, reheat the test tube until the sample reaches 50 ℃±1 ℃, then repeat the determination at a temperature 4 ℃ higher than the previous test temperature or at another higher temperature, until a test temperature at which the sample liquid surface moves is found.
• 9.1.7 After finding the temperature range of the freezing point (that is, the temperature range in which the liquid surface position changes from moving to not moving or from not moving to moving), select a temperature 2 ℃ lower than the temperature at which the sample can move, or 2 ℃ higher than the temperature at which the sample cannot move, and repeat the test. Repeat the test in this way until it is determined that at a certain test temperature the sample liquid surface stops moving and when raised by 2 ℃ the sample liquid surface can move again; take the temperature at which the sample liquid surface does not move as the freezing point of the sample.
• 9.1.8 If it is necessary to check whether the freezing point of the sample meets the specification value, the test should be carried out at 1 ℃ higher than the specification value; if the sample liquid surface can move at this time, the freezing point of the sample is considered to meet the specification value.

8.2 Automatic micro apparatus (only applicable to diesel distillate samples without additives)

• 9.2.1 Using manual injection or automatic injection, take a certain amount of test sample, and according to the instruction manual of the automatic micro cloud point tester, select an appropriate test program to start the test. When repeating the test, a new test sample should be replaced.
• 9.2.2 According to the displayed result on the automatic micro cloud point tester, record or print the final test result as the cloud point of the test sample.
  • Note: Before injection, first use air to push out all residual test sample from the previous test, then clean the injection tube with the test sample to be tested, and then start injection. Ensure that the injection tube is completely filled with the test sample and has no air bubbles (the presence of air bubbles will affect the stability of the test results). It is not recommended to use any organic solvent to clean the injection tube.

9. Qualitative and quantitative and calculation formula

• 10.1 Take the arithmetic mean of two test results from duplicate determinations as the cloud point of the test sample.
• 10.2 The manual cloud point tester shall report the cloud point of the test sample in accordance with the requirements of 9.1.7, and the result shall be accurate to 1 ℃.
• 10.3 The automatic micro cloud point tester shall report the cloud point of the test sample in accordance with the requirements of 9.2.2, and the result shall be accurate to 0.1 ℃.
• 10.4 If there is a dispute, the arbitration test shall be based on the cloud point test result of the manual apparatus.
• Calculation formula: not provided in the available source.

10. Precision

10.1 Precision of manual cloud point tester

• 11.1.1 Overview: Judge the reliability of test results according to the following provisions (95% confidence level).
• 11.1.2 Repeatability (r): The difference between two test results obtained by the same operator, in the same laboratory, using the same apparatus, according to the same method, on the same test sample in continuous determinations shall not exceed 2 ℃.
• 11.1.3 Reproducibility (R): The difference between two single, independent test results obtained by different operators, in different laboratories, using different apparatus, according to the same method, on the same test sample in separate determinations shall not exceed 4 ℃.

10.2 Precision of automatic micro cloud point tester (only applicable to diesel distillate samples without additives)

• 11.2.1 Overview: The precision statistical test of the automatic micro cloud point tester was carried out in six laboratories, using a total of 8 diesel distillate samples without additives, with a sample cloud point range of 3.8 ℃~-20.7 ℃, and was obtained after statistical calculation according to the relevant provisions of GB/T 6683. Judge the reliability of test results according to the following provisions (95% confidence level).
• 11.2.2 Repeatability (r): The difference between two test results obtained by the same operator, in the same laboratory, using the same apparatus, according to the same method, on the same test sample in continuous determinations shall not exceed 1.0 ℃.
• 11.2.3 Reproducibility (R): The difference between two single, independent test results obtained by different operators, in different laboratories, using different apparatus, according to the same method, on the same test sample in separate determinations shall not exceed 2.4 ℃.

10.3 Bias

• 11.3 This standard has not yet determined bias.

11. Report

• 10.1 Take the arithmetic mean of two test results from duplicate determinations as the cloud point of the test sample.
• 10.2 The manual cloud point tester shall report the cloud point of the test sample in accordance with the requirements of 9.1.7, and the result shall be accurate to 1 ℃.
• 10.3 The automatic micro cloud point tester shall report the cloud point of the test sample in accordance with the requirements of 9.2.2, and the result shall be accurate to 0.1 ℃.
• 10.4 If there is a dispute, the arbitration test shall be based on the cloud point test result of the manual apparatus.

12. Referenced documents

• GB/T 514—2005 Technical conditions for glass liquid thermometers for petroleum product testing
• GB/T 4756 Manual sampling method for petroleum liquids
• GB/T 6683 Determination method for precision data of petroleum product test methods
• GB/T 1.1—2009 (mentioned in the foreword, this standard was drafted according to the rules given therein)

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick reference for questions and answers