NB/SH/T 0639-2024 Determination of Thermal Stability of Petroleum Wax

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Card type: Test method

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

• Standard number: NB/SH/T 0639—2024
• Chinese title: Determination of Thermal Stability of Petroleum Wax
• English title: Test method for thermal oxidation stability of petroleum waxes
• Replacement relationship: replaces SH/T 0639—1996 "Determination of Thermal Stability of Paraffin Wax"
• Previous versions: first published in 1996 year SH/T 0639—1996; this is the first revision
• Publication/implementation: published on 2024-12-25, implemented on 2025-06-25
• Custodianship: Subcommittee on Petroleum Wax Products of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC3)
• Proposed by: China Petrochemical Corporation

2. Scope of application and non-applicability

• This document describes the method for determining the thermal stability of petroleum wax.
• Applicable to semi-refined paraffin wax, fully refined paraffin wax, packaging wax, food additive paraffin wax and other refined paraffin wax products, and non-light white oil products with a flash point (open cup) not exceeding 140℃.
• Not applicable: no explicit non-applicability clause is provided in the available source.

3. Method principle

Weigh 125g of test sample, place it in a 500mL heat-resistant beaker, oxidize at constant temperature at 170℃ for 30min, cool to a certain temperature, and then determine its Saybolt color number.

4. Reagents and materials (purity / preparation)

• 6.1 Cleaning solvent: analytical grade, anhydrous ethanol, petroleum ether, isooctane or other organic solvents.
• 6.2 Quality control sample: a stable petroleum wax product that can represent the characteristics of the sample to be tested may be used as a quality control sample. Periodically test this sample to check whether the system is in a satisfactory working state.
• Preparation method: not provided in the available source.

5. Apparatus and equipment

5.1 Manual apparatus

• 5.1.1 Heater: alcohol blowtorch (hanging-bottle type) or gas Bunsen burner, or a temperature-controllable electric heater.
• 5.1.2 Thermometer: softening point thermometer from 30℃ to 180℃, meeting the requirements for thermometer number GB-42 in GB/T 514—2005; or use another thermometer covering 170℃ with an accuracy of 0.5℃.
• 5.1.3 Heat-insulating gauze: clay gauze, diameter 8cm to 10cm.
• 5.1.4 Electric stirrer: rotation speed 100r/min±2r/min.
• 5.1.5 Iron stand: height 60cm to 70cm.
• 5.1.6 Saybolt colorimeter: meets the requirements of GB/T 3555.

5.2 Automatic apparatus

• 5.2.1 Automatic thermal stability tester: includes a temperature control unit, stirrer, timer, etc.; temperature control should be able to reach 170℃ with an accuracy of 0.1℃; stirring speed 100r/min±2r/min. The temperature control unit should be able to raise the sample temperature from 90℃ to 170℃ within 5min.
• 5.2.2 Automatic filter colorimeter: meets the requirements of NB/SH/T 0905.

5.3 General equipment

• 5.3.1 Heat-resistant beaker: made of stainless steel or glass, 500mL, diameter 77mm±2mm.
• 5.3.2 Oven or water bath: temperature control can reach up to 93℃ with an accuracy of 1℃.
• 5.3.3 Stirrer: made of glass or stainless steel, two blades, each blade diameter 16mm±1mm. The blades form an angle of 45° to 50° with the horizontal.
• 5.3.4 Electronic balance: accuracy 0.1g.

6. Recommended operating conditions

• Sample amount: 125g±1g
• Oxidation temperature: 170℃±2℃ (manual apparatus); 170℃±1.0℃ (automatic apparatus)
• Constant temperature time: 30min±10s (manual apparatus); 30min (automatic apparatus, tolerance not specified in the source text)
• Heating requirement: from about 90℃ to 170℃ within 5min (manual apparatus); from 90℃ to 169℃ within 5min (automatic apparatus)
• Stirring speed: 100r/min±2r/min
• Timing start point: start timing when the sample temperature rises to 169℃
• Thermometer position for manual apparatus: bottom end about 10mm from the bottom of the beaker, about 10mm from the inner wall of the beaker
• Stirrer blade position for manual apparatus: bottom end about 15mm to 20mm from the bottom of the beaker
• Temperature sensor position for automatic apparatus: about 10mm from the inner wall of the beaker, bottom end about 10mm from the bottom of the beaker
• Stirrer blade position for automatic apparatus: about 15mm to 20mm from the bottom of the beaker

7. Sampling and sample preparation

• 7 Sampling: sample according to SH/T 0229 (solid), GB/T 4756 or GB/T 27867 (liquid). Liquid samples may be tested immediately or cooled to room temperature.
• 8.1 Clean the beaker and stirrer thoroughly with cleaning solvent, dry them, and set aside.
• 8.2 If a manual apparatus is used, assemble the petroleum wax thermal oxidation apparatus according to Figure 1. The apparatus should be installed in a place without obvious air flow.
• 8.3 For paraffin wax samples, pre-melt in a water bath or oven to not higher than its melting point 17℃, stir evenly; the sample should not remain in the molten state for more than 1h.

8. Analytical procedure

9.1 Manual apparatus

• 9.1.1 Weigh 125g±1g of test sample, place it in a 500mL beaker, place the beaker on the heat-insulating gauze, and slowly heat the sample with a heater to about 90℃.
• 9.1.2 Place the thermometer and stirrer into the heated sample; the bottom end of the thermometer is about 10mm from the bottom of the beaker and about 10mm from the inner wall of the beaker; the bottom end of the stirrer blade is about 15mm to 20mm from the bottom of the beaker. Start the stirring motor and stir the sample at a speed of 100r/min±2r/min; the stirrer blade must not touch the thermometer. Immediately adjust the heater and heat the sample strongly so that the sample temperature rises from about 90℃ to 170℃ within 5min; start timing when the sample temperature rises to 169℃. Specific operation: when the sample temperature rises from about 90℃ to about 165℃, quickly remove the heater. When the sample temperature rises to 170℃ and no longer increases, place the heater back under the heat-insulating gauze, adjust the heater intensity, and keep the sample temperature constant at 170℃±2℃.
• 9.1.3 During the constant temperature process, adjust the heater intensity or its distance from the bottom of the heat-insulating gauze at any time according to temperature changes.
• 9.1.4 After maintaining constant temperature at 170℃±2℃ for 30min±10s, stop heating and stirring, and remove the beaker from the heat-insulating gauze. For paraffin wax samples, cool at room temperature for 5min, then place the beaker in a constant-temperature oven and keep at 85℃±5℃ for 15min. For white oil samples, cool to room temperature.
• 9.1.5 Determine the Saybolt color of the thermally oxidized sample according to the method in GB/T 3555.

9.2 Automatic apparatus

• 9.2.1 Weigh 125g±1g of test sample, place it in a 500mL beaker, place the beaker on the apparatus, insert the temperature sensor and stirrer; the temperature sensor is about 10mm from the inner wall of the beaker, and the bottom end of the sensor is about 10mm from the bottom of the beaker; the stirrer blade is about 15mm to 20mm from the bottom of the beaker; start the programmed heating according to the apparatus instructions. The sample should rise from 90℃ to 169℃ within 5min; start timing when the sample temperature rises to 169℃.
• 9.2.2 After the sample is kept at constant temperature at 170℃±1.0℃ for 30min, stop heating and stirring, and immediately remove the beaker from the apparatus. For paraffin wax samples, cool at room temperature for 5min, then place the beaker in a constant-temperature oven and keep at 85℃±5℃ for 15min. For white oil samples, cool to room temperature.
• 9.2.3 Determine the Saybolt color of the thermally oxidized sample according to the method in NB/SH/T 0905.
• Note: The Saybolt color of the thermally oxidized sample may also be determined according to GB/T 3555, but its precision has not been investigated.

9. Qualitative and quantitative determination and calculation formula

• The result is expressed as Saybolt color number.
• Manual apparatus: take the average of 2 results from replicate determinations (9.1.1 to 9.1.5), round to an integer as the test result, and report as Saybolt color number.
• Automatic apparatus: use the Saybolt color number measured by the apparatus as the test result of the sample.
• Arbitration: if there is a dispute over the test results of the two methods, the arbitration test shall be based on the thermal stability result from the manual apparatus.
• Calculation formula: not provided in the available source.

10. Precision

12.1 Manual apparatus

• 12.1.1 General: judge the reliability of the results according to the provisions of 12.1.2, 12.1.3 and a 95% confidence level.
• 12.1.2 Repeatability: in the same laboratory, by the same operator using the same equipment, according to the same test method, and testing the same sample independently within a short period of time, the difference between two independent test results obtained shall not exceed 1 Saybolt color number.
• 12.1.3 Reproducibility: in different laboratories, by different operators using different equipment, according to the same test method, testing the same sample independently, the difference between two independent test results obtained shall not exceed 2 Saybolt color number.

12.2 Automatic apparatus

• 12.2.1 General: an interlaboratory study was conducted in 8 laboratories on 8 white oil and 10 paraffin wax samples, and the precision of the automatic apparatus was statistically derived with reference to GB/T 6683.1. Judge the reliability of the results according to the provisions of 12.2.2, 12.2.3 and a 95% confidence level.
• 12.2.2 Repeatability: in the same laboratory, by the same operator using the same equipment, according to the same test method, and testing the same sample independently within a short period of time, the difference between two independent test results obtained shall not exceed 1.1 Saybolt color number.
• 12.2.3 Reproducibility: in different laboratories, by different operators using different equipment, according to the same test method, testing the same sample independently, the difference between two independent test results obtained shall not exceed 2.6 Saybolt color number.

12.3 Bias

Since the thermal stability result is obtained by defining a method, the bias of the test results of this method cannot be determined.

11. Report

• Manual apparatus: take the average of 2 results from replicate determinations (9.1.1 to 9.1.5), round to an integer as the test result, and report as Saybolt color number.
• Automatic apparatus: use the Saybolt color number measured by the apparatus as the test result of the sample.
• If there is a dispute over the test results of the two methods, the arbitration test shall be based on the thermal stability result from the manual apparatus.

12. Referenced documents

Normative referenced documents

• GB/T 514—2005 Technical conditions for glass liquid thermometers for petroleum product testing
• GB/T 3555 Determination of Saybolt color of petroleum products - Saybolt colorimeter method
• GB/T 4756 Petroleum liquids—Manual sampling
• GB/T 27867 Petroleum liquids—Automatic pipeline sampling
• NB/SH/T 0843 Evaluation of test systems in the petrochemical industry—Statistical techniques
• NB/SH/T 0905 Determination of colour of petroleum products—Automatic tristimulus method
• SH/T 0229 Sampling method for solid and semi-solid petroleum products

References

• [1] GB/T 6683.1 Petroleum and related products—Measurement methods and results precision—Part 1: Determination of precision data for test methods

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 Q&A