SH/T 0719-2002 Determination of Oxidation Induction Time of Lubricating Oils (Pressure Differential Scanning Calorimetry)

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Card type: Test method

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

• Method number: SH/T 0719-2002
• Chinese full name: Determination of Oxidation Induction Time of Lubricating Oils (Pressure Differential Scanning Calorimetry)
• English name: Standard test method for oxidation induction time of lubricating oils by pressure differential scanning calorimetry (PDSC)
• Replacement relationship: not provided in the available source (no mention of replacing any old standard)
• Adoption relationship: equivalent adoption of ASTM D 6186-98
• Main technical differences from ASTM D 6186-98: for thermal analyzers whose pressure differential scanning calorimeter test cell has no purge gas outlet, this standard adds content allowing testing by a capped sealing method
• Publication/implementation: published by 2002-05-31, implemented by 2002-07-01
• Publishing unit: State Economic and Trade Commission
• Responsible organization: Sinopec Petroleum Processing Research Institute
• Drafting unit: Refinery of Sinopec Shanghai Gaoqiao Branch
• Main drafter: Lu Meiyu
• Appendices: Appendix A and Appendix B are both informative appendices

2. Scope of application and non-applicability

• 1.1 This standard specifies the determination of the oxidation induction time of lubricating oils by pressure differential scanning calorimetry (PDSC method), with an oxygen pressure of 3.5 MPa and a temperature of 130℃ to 210℃.
• 1.2 This standard does not purport to address all safety problems. Users should establish appropriate safety and protective measures and determine applicable management systems before using this standard.
• Non-applicable scope: not provided in the available source.

3. Method principle

• 3 Method summary: Weigh a small amount of sample in a sample pan and place it in the test cell of the PDSC instrument. Heat the test cell of the PDSC instrument to the specified temperature, and after equilibration introduce oxygen at a certain pressure. The test cell of the PDSC instrument is maintained at the specified temperature and oxygen pressure until an oxidative exothermic reaction occurs. Measure the extrapolated inflection point time, and use this as the oxidation induction time of the lubricating oil at the specified test temperature.
• 4 Significance and use: The oxidation induction time measured under the conditions of this standard can be used to characterize the oxidation stability of lubricating oils. This standard is faster than other oxidation test methods for lubricating oils and uses a smaller amount of sample. It can be used for product research and development, quality control, and other specific purposes. However, the correlation between the results of this standard method and the service performance of lubricating oils has not yet been established. Appendix A provides a calculation method for predicting the oxidation induction time of lubricating oils at different test temperatures.

4. Reagents and materials (purity / preparation)

• 6.1 Oxygen: purity not less than 99.5% (volume). Warning: oxidizer. Gas is used under pressure.
• 6.2 Indium: purity not less than 99.9% (mass).
• 6.3 Balance: sensitivity 0.1 mg.
• Preparation of other reagents: not provided in the available source.

5. Instruments and equipment

• 5 Pressure differential scanning calorimeter (PDSC instrument) is shown in Figure 1, equipped with the following units:
  • 5.1 Aluminum sample pan: after sealing, it can withstand 3.5 MPa±0.2 MPa pressure under 210℃, and the pressure gauge scale division is 200 kPa or smaller. Aluminum SFI(Solid Fat Index) sample pans may also be used. Note: SFI sample pans have a more consistent surface area than standard flat-bottom pans and can improve reproducibility.
  • 5.2 Thermal analyzer.
  • 5.3 Oxidation stability software.
  • 5.4 Calibration software.
  • 5.5 Calibrated flowmeter: range at least 200 mL/min, scale division 5 mL or smaller.
  • 5.6 Sample sealing press. Note: Stainless steel or copper tubing is suitable for oxygen.
• Figure 1 PDSC instrument test unit: A- oxygen cylinder; B-PDSC instrument test cell; C- differential scanning calorimeter (DSC instrument); D- flowmeter; E- standard interface; F- computer; G- plotter (source-text extraction noise, letter labels require confirmation against the source standard).

6. Recommended operating conditions

• Oxygen pressure: 3.5 MPa±0.2 MPa
• Test temperature: 130℃, 155℃, 180℃, 210℃ (7.2.1 lists optional test temperatures)
• Oxygen flow rate: 100 mL/min±10 mL/min
• Heating rate: 10℃/min
• Sample amount: 3.0 mg±0.2 mg
• Equilibration time: equilibrate at the test temperature for 2 min
• Pressurization time: about 2 min to reach maximum pressure
• Timing start point: the measurement of the oxidation induction time starts when the oxygen valve is opened
• Test termination: close the oxygen valve after the oxygen valve has been open for 120 min; if the approximate oxidation induction time is known, the test may be stopped as soon as oxidative exotherm occurs

7. Sampling and sample preparation

• 8.2 Weigh 3.0 mg±0.2 mg of sample in the sample pan so that the sample is evenly distributed on the flat surface. Do not splash onto other parts of the sample pan. If the diffusion diameter of the sample in the sample pan exceeds 0.5 cm, a flat-bottom pan may be used.
• 8.3 Place the unsealed sample pan containing the sample on the platform of the test cell of the PDSC instrument; place an empty sample pan of the same specification on the reference platform. Close the test cell of the PDSC instrument and the pressure release valve.
• Adoption note: For thermal analyzers whose PDSC instrument test cell has no purge gas outlet, the sample pan is allowed to be capped and sealed (the cap has a small hole) to reduce contamination of the PDSC instrument test cell.
• Other sampling requirements: not provided in the available source.

8. Analytical procedure

• 7 Calibration
  • 7.1 Sample temperature calibration
    • 7.1.1 Weigh about 10 mg of indium in an aluminum sample pan, add a lid, and seal it with a sealing press. Place the sealed sample pan on the sample platform of the test cell of the PDSC instrument. Seal an empty pan in the same manner and place it on the reference platform. Cover the test cell of the PDSC instrument and close it.
    • 7.1.2 Gently open the oxygen cylinder valve, and use the pressure regulator to adjust the inlet pressure of the test cell of the PDSC instrument to 3.5 MPa±0.2 MPa. Open the inlet valve of the test cell of the PDSC instrument so that the pressure slowly fills the test cell of the PDSC instrument. After 2 min, adjust the outlet valve so that the oxygen flow rate through the flowmeter is 100 mL/min±10 mL/min.
    • 7.1.3 Heat the thermal analyzer from room temperature (about 22℃) to 180℃ at a heating rate of 10℃/min. After the run is completed, measure the melting point temperature of indium. If the measured temperature deviates from 157.4℃±0.2℃, calibrate according to the hardware or software calibration procedure described in the manufacturer's instrument manual. If a hardware calibration procedure is used, temperature calibration must be performed under conditions of an oxygen pressure of 3.5 MPa and a flow rate of 100 mL/min. A typical calibration curve is shown in Figure 2. Note: The melting point of indium at one atmosphere is 156.6℃, but under the oxygen pressure conditions of 3.5 MPa in this standard, its melting point rises to 157.4℃.
  • 7.2 Temperature controller calibration
    • 7.2.1 Remove the sample pan and reference pan from the test cell of the PDSC instrument, and close the test cell of the PDSC instrument. Slowly open the oxygen pressure to 3.5 MPa±0.2 MPa, and use the outlet valve of the test cell of the PDSC instrument to adjust the oxygen flow rate to 100 mL/min±10 mL/min. Select the required test temperature (210℃, 180℃, 155℃ or 130℃).
    • 7.2.2 Program the temperature so that the test cell of the PDSC instrument is maintained at the selected test temperature. After 10 min, if the difference between the displayed temperature and the selected temperature exceeds ±0.2℃, slowly adjust the temperature controller until they match. After adjustment, wait at least 5 min before continuing the next calibration step to check whether the temperature is stable. If the PDSC instrument does not have this function, the temperature controller should be calibrated according to the instrument manufacturer's recommendations.
  • 7.3 Calibration of the reference pressure gauge of the test cell of the PDSC instrument: use a calibrated pressure transducer or a pre-calibrated gauge, and calibrate according to the operation manual of the test cell of the PDSC instrument.
• 8 Test procedure
  • 8.1 Before starting the test, calibrate the temperature control of the thermocouple at the test temperature (210℃, 180℃, 155℃ or 130℃) according to steps 7.2.1 and 7.2.2. If the test temperature is unknown, calibration should be performed at 210℃.
  • 8.2 See Section 7.
  • 8.3 See Section 7.
  • 8.4 Starting from room temperature (about 22℃), heat the sample to the test temperature at a rate of 10℃/min.
  • 8.5 Equilibrate the sample at the test temperature for 2 min.
  • 8.6 Open the oxygen valve and slowly pressurize to 3.5 MPa±0.2 MPa. This takes about 2 min to reach maximum pressure. The measurement of the oxidation induction time starts when the oxygen valve is opened.
  • 8.7 When the pressure is balanced, check the flow rate of the test cell of the PDSC instrument and adjust it with the outlet valve to 100 mL/min±10 mL/min.
  • 8.8 After the oxygen valve has been open for 120 min, close the oxygen valve, and slowly release the pressure of the test cell of the PDSC instrument by opening the pressure release valve of the test cell of the PDSC instrument. If the approximate oxidation induction time is known, the test may be stopped as soon as oxidative exotherm occurs.
  • 8.9 Draw the thermal curve and measure the extrapolated inflection point time of the oxidative exotherm. Report this time, accurate to 1 min, as the oxidation induction time of the sample. If multiple oxidative exothermic peaks are observed, report the oxidation induction time of the largest oxidative exothermic peak. A typical thermal curve is shown in Figure 3.
  • 8.10 If the oxidation induction period is less than 10 min, the test should be repeated at a slightly lower temperature according to steps 8.2 to 8.9. Before retesting, the PDSC instrument test cell should be cooled to room temperature.

9. Qualitative and Quantitative and Calculation Formulas

• 2 Terms
  • 2.1 Extrapolated inflection point time extrapolated onset time: the time measured on the thermal curve, which is the intersection point of the baseline extrapolation line and the tangent at the maximum oxidation peak rate.
  • 2.2 Oxidation induction period oxidation induction time (OIT): the period during which the oxidation rate increases from zero to the maximum rate, and corresponds to the extrapolated inflection point time.
  • 2.3 Thermal curve thermal curve: a graphical representation of the heat flow of the specimen versus time.
• 9 Report
  • 9.1 Report the oxidation induction period of the specimen, accurate to 1 min.
  • 9.2 Report the test temperature.
• Appendix A (Informative appendix) Calculation of induction period
  • A1 The following kinetic formula can be used to predict the oxidation induction period of lubricating oils at different test temperatures:
    • t = A e^(2.303T₂/T₁) …… (A1) (source-text extraction noise, exponential form requires confirmation against the source standard)
    • A = OIT e^(-2.303T₂/T₁) …… (A2) (source-text extraction noise, exponential form requires confirmation against the source standard)
  • Where:
    • t— calculated oxidation induction period, min;
    • A— oxidation coefficient of the oil;
    • T₁—predicted temperature, K;
    • T₂—test temperature, K;
    • OIT— oxidation induction period at the test temperature, min.
  • Note: The correspondence between T₁, T₂ and source-text extraction in the formula and T₁, T₂ in the original text requires confirmation against the source standard (source-text extraction).

10. Precision

• 10.1 Precision: The precision of this test method was statistically tested in 8 laboratories at 4 different temperatures (130℃, 155℃, 180℃ and 210℃), on 13 specimens, with oxidation induction periods ranging from 10 min to 119 min. Appendix B gives the samples, data, and the PDSC instrument used by the operators in the statistical test.
  • 10.1.1 Repeatability: The difference between two results obtained by the same operator using the same instrument on the same sample for repeated determinations shall not exceed the following value (95% confidence level): r = 0.17X, where X— is the average of the two test results.
  • 10.1.2 Reproducibility: The difference between two results obtained by different operators in different laboratories on the same sample shall not exceed the following value (95% confidence level): R = 0.35X, where X— is the average of the two test results.
• 10.2 Bias: This test method has no bias, because the value of the oxidation induction period can only be defined by the test method.

11. Report

• 9.1 Report the oxidation induction period of the specimen, accurate to 1 min.
• 9.2 Report the test temperature.

12. Referenced Documents

• ASTM D 6186-98 "Determination of Oxidation Induction Period of Lubricating Oils (Pressure Differential Scanning Calorimetry)" (equivalent adoption)
• Other referenced documents: not provided in the available source.

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