GB/T 12709-1991 Determination of Ageing Characteristics of Lubricating Oils (Conradson Carbon Residue Method)

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Card type: Test method

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

• Standard number: GB/T 12709-91
• Chinese full name: Determination of Ageing Characteristics of Lubricating Oils (Conradson Carbon Residue Method)
• English name: Lubricating oils—Determination of aging characteristics—Conradson carbon residue method
• Replacement relationship: not provided in the available source
• The standard contains two methods:
  • A method: Method for increase in Conradson carbon residue after ageing with air blowing
  • B method: Conradson carbon residue method after ageing with air blowing in the presence of ferric oxide
• Approval/implementation: approved by the State Bureau of Technical Supervision on 1991-01-28, implemented on 1991-12-01
• Adoption relationship: equivalent adoption of Federal German Standard DIN 51352—1985 Part 1 and Part 2

2. Scope of application and non-applicability

A method (Chapter 1)

• Specifies a method for determining the ageing characteristics of petroleum-based lubricating oils.
• Applicable to petroleum-based lubricating oils with or without additives whose evaporation loss during the determination does not exceed 15% (m/m).
• Also applicable to lubricating oils of the antioxidant additive and ash-containing detergent-dispersant types.

B method (Chapter 10)

• Specifies a method for determining the ageing characteristics of petroleum-based premium lubricating oils.
• Applicable to petroleum-based premium lubricating oils whose evaporation loss during the determination does not exceed 20% (m/m).

Not applicable: not provided in the available source.

3. Method principle

A method (Chapter 3 Method summary)

• At a temperature of 200 ℃, air is passed into the sample twice to age it, each time for 6 h.
• The carbon residue values of the sample before and after ageing are determined in accordance with GB 268, and the increase in carbon residue is used to express the ageing characteristics of the lubricating oil.

B method (Chapter 12 Method summary)

• With ferric oxide as catalyst, the sample is aged by passing air at a temperature of 200 ℃ for 24 h, after which the carbon residue value of the aged sample is determined in accordance with GB 268.

4. Reagents and materials (purity / preparation)

A method (4.2 materials)

• Air: purified air that is oil-free and dry.

B method (13.2, Chapter 14)

• Materials: same as A method 4.2 clause.
• Ferric oxide: analytical reagent grade, content not less than 99%.

5. Apparatus and equipment

A method (4.1 apparatus)

• 4.1.1 tester: composed of an ageing tube, a tube support, an air inlet tube and an exhaust tube, all parts made of borosilicate glass.
  • 4.1.1.1 ageing tube: dimensions as shown in the original figure.
  • 4.1.1.2 tube support: dimensions as shown in the original figure, fused to the air inlet tube; the air inlet tube is placed at the center of the ageing tube, and the distance between its lower end and the bottom of the ageing tube is 1±0.5 mm.
• 4.1.2 temperature measuring tube: same as specified in 4.1.1.1, but without a joint.
• 4.1.3 forced-air drying oven.
• 4.1.4 heating device: a well-insulated oil bath including a stirrer, a cover and a thermostatic regulator, whose performance shall keep the temperature of each sample in the bath at 200±1.0 ℃; at this temperature, the oil level of the oil bath shall be filled to 13 mm from the bath cover; a calibrated thermometer meeting the requirements of 4.1.5 is inserted into the temperature measuring tube, and oil is filled in the temperature measuring tube to the 110 mm mark. The support for the ageing tubes in the oil bath is fixed so that the ageing tubes are immersed in the oil to 140 mm; the oil bath cover is drilled with several round holes whose diameter is just sufficient to insert one ageing tube. To prevent the part of the ageing tube exposed above the oil bath and the thermometer from being affected by external air flow, the wall of the oil bath shall be about 150 mm higher than the bath cover, or a shield of the same size shall be provided above the oil bath cover. A metal bath may also be used as the heating device, but the temperature of the sample in each ageing tube must always be kept at 200±1.0 ℃, and the same shield shall be provided.
  • Note: Filling the gap between the metal block and the ageing tube with a suitable silicone liquid (requires confirmation against the source standard (source-text extraction), suspected to be "silicone oil liquid") can achieve a better heat transfer effect.
• 4.1.5 thermometer: shall meet the requirements listed in Table 1.
• 4.1.6 air filter: a washing bottle filled with glass wool.
• 4.1.7 air flowmeter: 40~400 mL/min, or other suitable air flowmeter, with an air flow rate of 15 L/h. When the air temperature is 20 ℃, the maximum error of the flowmeter is 0.25 L/h; one air flowmeter is used for each ageing tube.

Table 1 Thermometer specifications

B method (13.1 apparatus)

• 13.1.1 tester: temperature measuring tube, forced-air drying oven, heating device, thermometer, air filter and air flowmeter, same as A method 4.1 clause.
• 13.1.2 high-temperature furnace: adjustable to 775±25 ℃.
• 13.1.3 high-efficiency disperser:
  • Rotation speed: about 20 000 r/min;
  • Peripheral speed: 13 m/s;
  • Shaft length: 200 mm;
  • Shaft diameter: 18 mm.

6. Recommended operating conditions

A method

• Ageing temperature: 200±1.0 ℃ (4.1.4, 6.2)
• Air flow rate: 15±0.25 L/h (7.1)
• Ageing process: pass air twice, each time for 6 h; between the two, leave at room temperature for 12~18 h (7.1)
• For non-arbitration tests, an ageing process of 1×12 h is permitted (7.1 Note)
• Sample injection temperature: 18~28 ℃ (7.1)

B method

• Ageing temperature: 200±1.0 ℃ (17.1)
• Air flow rate: 15±0.25 L/h (17.1)
• Ageing time: 24 h (17.1)
• High-temperature furnace temperature: 775±25 ℃ (13.1.2, 17.3)
• Sample injection temperature: 18~28 ℃ (17.1)

7. Sampling and sample preparation

• A method (Chapter 5): carried out in accordance with GB 4756.
• B method (Chapter 15): carried out in accordance with GB 4756.

8. Analytical procedure

A method

6 Preparation

• 6.1 Preparation of apparatus: first clean the glassware used with chromic acid cleaning solution, then rinse separately with tap water and distilled water until the distilled water shows a neutral reaction, then dry in a drying oven (glassware may be rinsed with solvent).
• 6.2 Heat the heating device to 200±1.0 ℃.

7 Test procedure

• 7.1 Ageing: inject 18–28 ℃ of sample into the ageing tube up to the 40 mL mark, attach the tube support, and weigh to 0.1 g. Then place it in the heating device and introduce air so that the air flow rate passing through the sample is 15±0.25 L/h. After 6 h, stop introducing air, remove the tester from the heating device, leave at room temperature for 12–18 h, and then carry out this ageing process again under the same conditions for 6 h.
  • Note: For non-arbitration tests, an ageing process of 1×12 h is permitted.
• 7.2 Determination of evaporation loss: after ageing is completed, remove the tester from the heating device, cool to room temperature, weigh, and calculate the evaporation loss (if the sample density is unknown, for convenience of calculation, its density may be assumed to be 0.900 g/mL).
• 7.3 Determination of carbon residue: after thoroughly mixing the aged sample, determine the carbon residue in accordance with GB 268. For lubricating oils containing ash additives, the amount of aged sample may be reduced to 5 g (requires confirmation against the source standard (source-text extraction), the original text reads "58"). If the aged sample has been left standing for a long time, before determining the carbon residue, heat the sample in a water bath at 100 ℃ for 20 min and mix thoroughly.

B method

16 Preparation

• Same as A method Chapter 6.

17 Test procedure

• 17.1 Aging: Inject approximately 13 mL of a sample of 18~28 ℃ into the aging tube, then add 0.4±0.005 g of ferric oxide, slowly tap the aging tube to disperse the ferric oxide throughout the sample, then inject the sample into the aging tube up to the 40 mL mark, stir with a high-efficiency diffuser for 30 s to uniformly disperse the ferric oxide in the sample. Next, lift the high-efficiency diffuser out of the oil surface, drain oil for 10 s, and in order to calculate evaporation loss, weigh the test apparatus into which the sample has been injected, to 0.1 g, and place it in the heating device. The temperature of each sample in the test apparatus shall be maintained at 200±1.0 ℃, and air shall be passed into the sample at a rate of 15±0.25 L/h; after maintaining for 24 h, stop passing air and remove the test apparatus from the heating device.
• 17.2 Determination of evaporation loss: After aging, the sample is cooled to room temperature and weighed together with the test apparatus, to 0.1 g, and the evaporation loss of the sample is calculated (if the density of the sample is unknown, the density may be assumed to be 0.900 g/mL).
• 17.3 Determination of the mass of carbon residue and ferric oxide: Before determination, first use a glass rod with a diameter of 6 mm to disperse the ferric oxide at the bottom of the aging tube, and stir thoroughly. Then stopper tightly with a glass stopper, and shake for 1 min to make it uniform. If the aged sample is very viscous, it may be placed in a water bath at about 100 ℃ and heated for 20 min, then after shaking uniformly as described above, immediately take out 5 g of the hot aged sample and place it into a weighed crucible, transfer to a desiccator, cool to room temperature, and determine the carbon residue value according to GB 268, which is the total mass of carbon residue and ferric oxide. Place the crucible with residue into a high-temperature furnace at 775±25 ℃ for 2 h, then take it out and place it in a desiccator to cool to room temperature, and weigh the mass of ferric oxide.
  • Note: If the sample foams over during the determination of carbon residue, the reduced mass shall be reported together with the result.

9. Qualitative and Quantitative and Calculation Formulas

A Method (Chapter 8 Calculation and Reporting)

• Use the carbon residue value of the same sample without aging and the average of two carbon residue values after aging to calculate the carbon residue increase, and express the determination result as the absolute increase in carbon residue [taken to 0.05% (m/m)].

B Method (Chapter 18 Calculation)

18.1 The evaporation loss of the sample X₁ [% (m/m)] is calculated according to formula (1):

X₁ = (m₁ − m₂) / m₃ × 100 …… (1)

Where:

• m₁ — total mass of the test apparatus, sample, and ferric oxide before aging, g;
• m₂ — total mass of the test apparatus, sample, and ferric oxide after aging, g;
• m₃ — mass of the sample, g.

(Note: In the original text source-text extraction, the symbols m₁, m₂, m₃ are noisy; the above is organized according to context and requires confirmation against the source standard (source-text extraction).)

18.2 The carbon residue of the sample after aging X₂ [% (m/m)] is calculated according to formula (2):

X₂ = (m₄ − m₅) / (m₄ − m₆) × 100 …… (2)

Where:

• m₄ — mass of the aged sample taken when determining carbon residue, g;
• m₅ — total mass of carbon residue and ferric oxide, g;
• m₆ — mass of ferric oxide, g.

(Note: In the original text source-text extraction, the symbols m₄, m₅, m₆ are noisy; the above is organized according to context and requires confirmation against the source standard (source-text extraction).)

10. Precision

Judge the reliability of test results according to the following provisions (95% confidence level).

A Method (Chapter 9)

• 9.1 Repeatability: The difference between two results obtained by the same operator in repeated determinations shall not exceed the value listed in Table 2.
• 9.2 Reproducibility: The difference between two results provided by two laboratories shall not exceed the value listed in Table 2.

Table 2 Precision % (m/m)

Note: 1) This value was obtained by statistical testing of samples with Conradson carbon residue values between 0.9~1.9% (m/m).

(Note: In Table 2, the correspondence between “percentage of the average (%)” and the numerical values source-text extraction is poorly typeset and requires confirmation against the source standard (source-text extraction).)

B Method (Chapter 19)

• 19.1 Repeatability: The difference between two results obtained by the same operator in repeated determinations shall not exceed 20% of their average.
• 19.2 Reproducibility: The difference between two results provided by two laboratories shall not exceed 40% of their average.

11. Reporting

A Method (Chapter 8)

• Use the carbon residue value of the same sample without aging and the average of two carbon residue values after aging to calculate the carbon residue increase, and express the determination result as the absolute increase in carbon residue [taken to 0.05% (m/m)].

B Method (Chapter 20)

• Take the average of two determination results of the same sample as the determination result of carbon residue, taken to 0.05% (m/m).

12. Referenced Documents

• GB 268 Petroleum products — Determination of carbon residue (Conradson method)
• GB 4756 Petroleum and liquid petroleum products — Sampling (manual method)

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