SH/T 0193-2008 Determination of oxidation stability of lubricating oils — Rotating oxygen bomb method

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Card type: Test method

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

• Standard number: SH/T 0193-2008 (the original cover source-text extraction writes "SHLT 0193-2008", the body page header writes "SH/T 0193—2008", requires confirmation against the source standard (source-text extraction))
• Chinese name: Determination of oxidation stability of lubricating oils — Rotating oxygen bomb method
• English name: Lubricating oils—Determination of oxidation stability—Rotating pressure vessel method
• Replacement relationship: replaces SH/T 0193—1992 "Determination method for oxidation stability of lubricating oils (rotating oxygen bomb method)"; SH/T 0193—1992 refers to and adopts ASTM D2272-85
• Adoption relationship: This standard modifies and adopts ASTM D2272-02 "Determination method for oxidation stability of turbine oils — Rotating oxygen bomb method", and has been redrafted according to ASTM D2272-02
• Main technical differences from ASTM D2272-02 (foreword): the standard name is changed to "Determination of oxidation stability of lubricating oils — Rotating oxygen bomb method"; the referenced standards are changed to the corresponding national standards of our country; referring to ASTM D2112-01, relevant technical content for the determination of inhibited mineral insulating oils under 140 ℃ is added; Annex B "Thermometer specifications" is added
• Main changes from SH/T 0193—1992 (foreword): the catalyst coil cleaning solution is changed to isopropanol and acetone is added; the copper wire diameter is changed to 1.63 mm±0.01 mm and the requirement to comply with GB/T 3953 is added; the requirement that test water comply with the grade 2 water specification of GB/T 6682 is added; two chapters, "Significance and use" and "Sampling", are added; in instrument preparation, the catalyst coil outer diameter is changed to 44 mm~48 mm and a mass requirement is added; in test procedure 9.2, Note 1 is added; in 9.4, Note 1 and Note 2 are added, and Figure 2 pressure-time curve is added; the precision provisions are changed; the report is changed to reporting results according to Figure 2; Annex A adds instrument material and specification requirements and Figures A.2, A.4, A.5, A.6, A.7; Annex B is added
• Nature of annexes: Annex A and Annex B are both normative annexes
• Publication/implementation: published on 2008-04-23, implemented on 2008-10-01
• Proposed by/administrated by/drafted by: proposed by China Petrochemical Corporation; administrated by the Petrochemical Research Institute of China Petroleum & Chemical Corporation; drafting organization: Petrochemical Research Institute of China Petroleum & Chemical Corporation; participating drafting organization: Hunan Electric Power Research Institute; main drafters: Bo Yanhong, Chen Shaohong, Qian Hui, Wang Ruicai (names require confirmation against the source standard (source-text extraction))

2. Scope of application and non-applicability

• 1.1 uses an oxygen pressure vessel (oxygen bomb), in the presence of water and a copper catalyst, at 150 ℃ to evaluate the oxidation stability of new and in-service turbine oils having the same composition (base oil and additives).
• 1.2 can also, under the conditions of 140 ℃, rapidly evaluate the oxidation stability of new mineral insulating oils containing 2,6- di-tert-butyl-p-cresol and/or 2,6- di-tert-butylphenol antioxidants.
• 1.2 is not applicable to the determination of mineral insulating oils containing antioxidants whose viscosity at 40 ℃ is greater than 12 mm²/s (the original source-text extraction writes "12mm'/s", requires confirmation against the source standard (source-text extraction)).
• Units used in 1.3: International System of Units (SI) units.
• 1.4 This standard involves certain hazardous materials, operations and equipment, but it is not intended to address all safety issues associated with them; users should establish appropriate safety and protective measures before use and determine applicable management regulations. For special warning statements see 6.2, 6.4, 6.5, 6.6, 6.10 and 6.11 (the correspondence between the clause numbers listed in the original and the warning clauses in the body requires confirmation against the source standard (source-text extraction)).

3. Method principle

Place the test sample, water and copper catalyst coil into a covered glass sample container, and place it in an oxygen bomb equipped with a pressure gauge. The oxygen bomb is filled with oxygen at a pressure of 620 kPa, placed in a specified constant-temperature oil bath (turbine oil 150 ℃, mineral insulating oil 140 ℃), and rotated axially at a speed of 100 r/min at an angle of 30° to the horizontal plane. The time required for the test to reach the specified pressure drop (min) is the oxidation stability of the test sample.

4. Reagents and materials (purity / preparation)

• 6.1 Isopropanol: analytical reagent. Warning—flammable, harmful to health.
• 6.2 Liquid detergent.
• 6.3 n-Heptane: analytical reagent, purity not less than 99.0% (mole fraction). Warning—flammable, harmful to health.
• 6.4 Oxygen: purity not less than 99.5%, pressure adjustable to 620 kPa. Warning—strongly supports combustion.
• 6.5 Alcoholic potassium hydroxide solution (1%): dissolve 12 g potassium hydroxide in 1 L isopropanol solution. Warning—flammable, harmful to health.
• 6.6 Silicon carbide abrasive cloth: grit 100.
• 6.7 Silicone grease.
• 6.8 Catalyst coil: electrolytic copper wire, diameter 1.63 mm±0.01 mm, purity 99.9%, complying with the provisions of GB/T 3953; soft copper wire of the same grade may also be used (the original source-text extraction writes "1.03imm 0.01 mm", which is inconsistent with the foreword "1.63 mm±0.01 mm" and Annex A Figure A.1 "1.63 mm diameter", requires confirmation against the source standard (source-text extraction)).
• 6.9 Solvent naphtha: complies with the provisions for No. 2 or No. 3 solvent naphtha in GB 1922 (the original source-text extraction writes "®BM922", requires confirmation against the source standard (source-text extraction)). Warning—flammable, harmful to health.
• 6.10 Acetone: analytical reagent. Warning—flammable, harmful to health.
• 6.11 Water: complies with the grade 2 water specification of GB/T 6682.
• Note: The body of clause 9.1 cites "water complying with the provisions of 6.12", but Chapter 6 does not contain clause 6.12; the clause number requires confirmation against the source standard (source-text extraction).

5. Instruments and equipment

• The rotating oxygen bomb test assembly includes: oxygen bomb, glass sample container with a polytetrafluoroethylene cover having four holes, retaining spring, catalyst coil, pressure gauge, thermometer and test oil bath, as detailed in Annex A; the instrument schematic is shown in Figure 1.
• Annex A (normative annex) Rotating oxygen bomb instrument test equipment:
  • A.1 Oxygen bomb, oxygen bomb body: the oxygen bomb body and flat cover are made of 0Cr18Ni10Ti stainless steel to ensure good heat transfer, and the inner surface must be smooth for easy cleaning; it may also be made of 76.2 mm copper rod, but must be thickly chrome-plated (the original source-text extraction writes "OC18N 1OTi" "76.2mg", requires confirmation against the source standard (source-text extraction)).
  • A.1.2 The bomb stem shall be made of stainless steel, with an inner diameter of 6.4 mm, and fitted with a 6.4 mm needle valve.
  • A.1.3 The locking ring is made of chrome-plated steel or chrome-plated aluminum bronze.
  • A.1.4 The oxygen bomb shall be able to withstand a pressure of 3450 kPa at 150 ℃.
  • A.1.5 The O-shaped sealing ring is made of fluoro rubber or silicone rubber, with an inner diameter of 50.8 mm and an outer diameter of 60.3 mm; for the larger concave sealing groove on the flat cover, a O-shaped sealing ring with an inner diameter of 54 mm and an outer diameter of 60.3 mm is required.
  • A.2 Glass sample container: made of borosilicate glass, capacity 175 mL, with a copper catalyst coil; it shall be able to slide into and be fixed in the oxygen bomb body without clearance; wall thickness not greater than 2.5 mm, mass not more than 100 g.
  • A.2.1 The top of the glass sample container shall be covered with a polytetrafluoroethylene cover having a diameter of 57.2 mm, with four holes of diameter 3.2 mm on the cover, each hole located at a distance of 9.5 mm from the center of the cover; cover thickness 1.6 mm; use the stainless steel retaining spring shown in Figure A.6 to ensure rotation of the sample container; the assembly drawing is shown in Figure A.7.
  • A.3 Recording equipment: A.3.1 recorder (Figure A.8) or indicating pressure gauge, range 0 kPa–1400 kPa, graduation 25 kPa, accuracy of 2.5% of the total scale interval or smaller; the automatic recording pressure gauge shall be installed so that the plane of the pressure gauge is perpendicular to the axis of rotation. A.3.2 Pressure measurement system: includes an electronic pressure transducer, power supply, mounting device and connecting wires; the rotating transducer connector is directly fixed on the oxygen bomb stem to replace the standard mechanical pressure recorder; pressure transducer range 0 kPa–1400 kPa; the output signal is led to a data recorder, a recorder based on a microprocessor, or a computer that collects data; the data collection instrument must be able to collect pressure-time data; the data accuracy of the entire system is within 2.5% of the total scale.
  • A.4 Test oil bath: equipped with a high-efficiency stirrer and appropriate control instruments and a rotating frame, so that after the oxygen bomb is inserted into the rotating frame it can be immersed at least 25 mm below the liquid surface, and rotate axially at an angle of 30° at a speed of 100 r/min±5 r/min.
  • A.4.1 The oil bath depth is at least 230 mm, filled with 30 L oil; silicone oil must be poured into the oil bath in a fume hood to avoid diffusion of generated oil vapor.
  • A.4.2 Provide temperature control so that the oil bath temperature is maintained within 0.1 ℃ of the test temperature; after the oxygen bomb is placed in, within 15 min, the test oil bath can automatically return to the test temperature.
  • A.5 Thermometer: For turbine oil, use a IP37C thermometer, range 144 ℃~156 ℃, graduation value 0.2 ℃, technical specifications are detailed in Appendix B Table B.1 or other temperature measuring equipment with an accuracy of 0.1 ℃; for mineral insulating oil, use a ASTM 96C thermometer, range 120 ℃~150 ℃, graduation value 0.1 ℃, technical specifications are detailed in Appendix B Table B.2.
  • A.6 Pressure gauge: measures the pressure inside the oxygen bomb up to 620 kPa, graduation value 1.5 kPa.
• Appendix B (Normative Appendix) Thermometer technical specifications: B.1 The technical specifications of thermometers for turbine oil and mineral insulating oil tests are detailed in Table B.1 and Table B.2.
  • Table B.1 Thermometer technical specifications for turbine oil tests: temperature range 144 ℃–156 ℃; immersion depth 100 mm; scale markings 0.2; graduation value 1 ℃ (the original layout is suspected to be graduation value 0.2 ℃, long scale line interval 1 ℃, requires confirmation against the source standard (source-text extraction)); long scale line interval 2; numbered scale interval 0.15; maximum scale line width 0.2; indication tolerance 0.2; safety bulb required; maximum permissible heating temperature 260 ℃–280 ℃; total length 5.0 mm–8.0 mm (suspected misalignment between 260–280 and total length, requires confirmation against the source standard (source-text extraction)); stem outer diameter 10–25; sensing bulb length ≤ stem outer diameter; sensing bulb outer diameter 150°; scale line position 170–210; distance from sensing bulb bottom to scale line 50–80; scale range length 120–150.
  • Table B.2 Thermometer technical specifications for mineral insulating oil tests: temperature range 76; immersion depth 0.1; scale markings 0.5; graduation value 1.0; long scale line interval 0.15; numbered scale interval 0.2; maximum scale line width 190; indication tolerance 365–375; safety bulb 6.0–7.0; maximum permissible heating temperature 18–28; total length ≥5 and ≤ stem outer diameter; stem outer diameter 120°; sensing bulb length 116–130; sensing bulb outer diameter 185~219; scale line position 41; distance from sensing bulb bottom to scale line not provided in the available source; scale range length not provided in the available source; maximum distance from middle bulb top to sensing bulb bottom not provided in the available source. (The correspondence between the values in Table B.2 and the items is severely misaligned, requires confirmation against the source standard (source-text extraction) unclear in the source text (source-text extraction))

6. Recommended operating conditions

• Test temperature: turbine oil 150 ℃; mineral insulating oil 140 ℃.
• Initial oxygen pressure: 620 kPa (at room temperature 25 ℃).
• Rotation speed: 100 r/min±5 r/min.
• Rotation angle: axial rotation at an angle of 30° to the horizontal plane.
• Temperature stability: maintain the test temperature within the range of ±0.1 ℃.
• Pressure correction: For turbine oil, for each degree the temperature is above or below 25 ℃ room temperature 2.0 ℃, the pressure shall be increased or decreased correspondingly by 5 kPa; for insulating oil, for each degree the temperature is above or below 25 ℃ room temperature 2.8 ℃, the pressure shall be increased or decreased correspondingly by 7 kPa (the original source-text extraction is written as "7kR", requires confirmation against the source standard (source-text extraction)).
• Oil bath immersion: after the oxygen bomb is inserted into the rotating frame, it can be immersed at least 25 mm below the liquid surface.

7. Sampling and sample preparation

• 7.1 Samples can be obtained from oil tanks, drums, small containers, or operating equipment. The sampling method and equipment are specified in GB/T 4756.
• Sample amount: 50 g±0.5 g (see 9.1).
• Use a new catalyst coil for each sample (see 8.1).

8. Analytical procedure

• 8.1 Preparation of catalyst: Before use, polish a copper wire of length 3 m with silicon carbide abrasive cloth, and wipe the abrasive dust off the copper wire with a clean, dry cloth; wind the copper wire into a coil with an outer diameter of 44 mm–48 mm, a weight of 55.6 g±0.3 g, and an extended height of 40 mm–42 mm; clean with isopropanol and dry with air; if necessary, rotate and insert the coil into the glass sample container; use a new coil for each sample; if a longer storage time is required, the coil can be stored in a dry inert gas; for overnight storage (less than 24 h), the coil can be placed in n-heptane. Note: Packaged commercial coils prepared as described in 8.1 can also be used for this test.
• 8.2 Cleaning of the oxygen bomb: Clean the inside of the oxygen bomb body, flat cover, and bomb stem with hot liquid detergent, and rinse thoroughly with water; rinse the inside of the bomb stem with isopropanol and blow dry with clean compressed air; if after simple cleaning the inside of the oxygen bomb body, flat cover, and bomb stem still has an acidic odor, clean with 4% alcoholic potassium hydroxide solution and repeat the above steps. Warning—Failure to eliminate oxidation residues will adversely affect test results.
• 8.3 Cleaning of glass containers: First clean and rinse with a suitable solution (solvent naphtha or acetone), then soak or scrub in an aqueous detergent solution; scrub and rinse thoroughly with tap water, then rinse with isopropanol and distilled water, and finally dry with air; if there are insoluble substances, soak overnight in an acidic solution and repeat starting from the tap water rinsing step.
• 8.4 Cleaning of polytetrafluoroethylene cover: Remove residual oil traces with a suitable solvent and rinse clean with detergent solution; rinse thoroughly with tap water, then rinse with distilled water, and finally dry with air.
• 9.1 Bomb loading: Weigh the mass of the glass sample container containing the new clean catalyst coil; add 50 g±0.5 g of sample to the sample container and add 5 mL of water conforming to the specifications of 6.12; additionally add 5 mL of water conforming to the specifications of 6.12 to the bomb body, and gently slide the sample container into the bomb body (see Note); cover the sample container with a polytetrafluoroethylene cover, and place a fixing spring on top of the polytetrafluoroethylene cover; apply a thin layer of silicone grease to the outer layer of the O-shaped sealing ring in the sealing groove of the oxygen bomb flat cover to provide lubrication, and insert the oxygen bomb flat cover into the oxygen bomb body. Note: The water between the oxygen bomb body and the sample container helps heat transfer.
• 9.1.1 Used to tighten the locking ring; apply a thin layer of silicone grease to the threads of the pressure gauge threaded joint (polytetrafluoroethylene tape can replace silicone grease), and screw the pressure gauge into the top center of the oxygen bomb groove; connect the oxygen line connected to the pressure gauge to the inlet valve of the oxygen bomb stem; slowly open the oxygen supply valve until the pressure reaches 620 kPa, close the oxygen supply valve, loosen the joint or use a bleed valve to slowly release the pressure; repeat the purging step two more times, and the above purging step should last about 3 min; adjust the oxygen regulating valve to make the pressure reach 620 kPa at room temperature 25 ℃; for turbine oil, for each degree the temperature is above or below 25 ℃ room temperature 2.0 ℃, the pressure should be increased or decreased correspondingly by 5 kPa, for insulating oil, for each degree the temperature is above or below 25 ℃ room temperature 2.8 ℃, the pressure should be increased or decreased correspondingly by 7 kPa, to obtain the required initial pressure; after the oxygen bomb is filled to the required pressure, close the inlet valve tightly by hand; if necessary, immerse the oxygen bomb in water to check for leaks. Note: After the leak test, dry the oxygen bomb with a towel or a hair dryer to avoid bringing water into the hot test oil bath and causing oil splashing.
• 9.2 Oxidation: Under stirring, bring the oil bath to the specified test temperature (150 ℃ for turbine oil, 140 ℃ for insulating oil); turn off the stirrer, insert the oxygen bomb into the rotating frame, and record the time; restart the stirrer; if an additional heater is used, keep it running for the first 5 min and then turn it off (see Note 1); within 15 min after the oxygen bomb is inserted into the oil bath, the oil bath temperature shall stabilize to the test temperature; maintain the test temperature within the range of ±0.1 ℃ (see Note 2). Note 1: For different instrument configurations, the time for the oil bath to reach the test temperature after inserting the oxygen bomb is different. The instrument used should be investigated to obtain a set of conditions such that after the oxygen bomb is inserted, the oil bath temperature fluctuation does not exceed 2 ℃ and the oxygen bomb pressure reaches the steady state shown in curve A of Figure 2 within 30 min. Note 2: Throughout the entire test, maintaining the test temperature within the range of ±0.1 ℃ is a very important factor for the repeatability and reproducibility of test results.
• 9.3 Throughout the entire test, keep the oxygen bomb fully immersed and rotating continuously at a uniform speed; the standard rotation speed is 100 r/min±5 r/min, and any perceptible fluctuation in rotation speed will lead to erroneous results.
• 9.4 When the pressure drops from the maximum point by more than 175 kPa, the test ends (see Note 1); the pressure drop of 175 kPa usually corresponds to the rapid pressure drop of the induction period method, but does not always correspond; when it does not correspond, the operator should question the validity of the test (see Note 2). Note 1: The standard test procedure is that when the pressure drop reaches 175 kPa, the test ends; however, the operator may also choose a smaller pressure drop, or choose a pre-set approximate test time of 100 min to observe the condition of the oil and end the test, 100 min is far lower than the induction period of new oil containing antioxidants. Note 2: A typical test is shown in curve A of Figure 2; the maximum pressure is expected to be reached within 30 min, forming a stable pressure stage, and then the rapid pressure drop of the induction period method can be observed; in curve B, before the turning point of the induction period method is reached, the pressure has a gradual decrease, which is difficult to evaluate; although some synthetic liquids produce this type of curve, the gradual decrease in pressure may be caused by leakage of the oxygen bomb; if leakage is suspected, repeat the test with another oxygen bomb; if the repeated test still gives the same type of curve, the test result is valid.
• 9.5 After the test ends, remove the oxygen bomb from the oil bath and cool to room temperature; as soon as possible, immerse the oxygen bomb in light mineral oil and stir it a few times to quickly wash off the bath oil adhering to it; wash the oxygen bomb with hot water and soak it in cold water to quickly reach room temperature; the oxygen bomb may also be allowed to cool to room temperature in air; release the excess oxygen pressure and open the oxygen bomb.

9. Qualitative and Quantitative and Calculation Formulas

• 10.1 Expression of results:
  • 10.1.1 According to curve A of Figure 2, observe and record the pressure-time curve and establish the stable pressure in the curve (see Note 2 of 9.4); record the time for the pressure to drop from the stable pressure by 175 kPa; if it is a repeated test, the difference between the two stable pressures shall not exceed 35 kPa.
  • 10.1.2 According to curve B of Figure 2, observe and record the pressure-time curve and establish the maximum pressure reached by the test within the initial 30 min (see Note 2 of 9.4); record the time for the pressure to drop from the maximum pressure by 175 kPa; if it is a repeated test, the difference between the two maximum pressures shall not exceed 35 kPa.
• 10.2 Reporting of results:
  • 10.2.1 According to curve A of Figure 2, the oxidation life of the sample is the time from the start of the test until the pressure drops from the stable pressure by 175 kPa (min); according to curve B of Figure 2, the oxidation life of the sample is the time from the start of the test until the pressure drops from the maximum pressure by 175 kPa (min). Note: In the result report, it is recommended to indicate whether the test used a stainless steel or chrome-plated copper oxygen bomb.
• Calculation formulas (for precision):
  • Turbine oil repeatability: r = 0.12X (1), where X— is the arithmetic mean of repeated measurement results, min.
  • Turbine oil reproducibility: R = 0.22X (2), where X— is the arithmetic mean of two independent measurement results, min.

10. Precision

• 11.1 Precision: The reliability of test results is judged according to the following provisions (95% confidence level).
• 11.1.1 Repeatability (r): For the same operator using the same instrument to measure the same sample, the difference between successive measurement results shall not exceed 23 min for mineral insulating oil; for turbine oil, it shall not exceed the value specified by formula (1): r = 0.12X, where X— is the arithmetic mean of repeated measurement results, min.
• 11.1.2 Reproducibility (R): For different operators in different laboratories measuring the same sample, the difference between two independent results shall not exceed 43 min for mineral insulating oil; for turbine oil, it shall not exceed the value specified by formula (2): R = 0.22X, where X— is the arithmetic mean of two independent measurement results, min.
• 11.2 Bias: This method has not established bias.

11. Report

• See 10.1, 10.2.
• 10.2.1 Report the oxidation life of the sample (min), according to curve A or curve B, respectively, as the time for the stable pressure or maximum pressure to drop by 175 kPa.
• Note: In the result report, it is recommended to indicate whether the test used a stainless steel or chrome-plated copper oxygen bomb.

12. Normative References

• GB 1922 Solvent naphtha for paints and cleaning
• GB/T 3953 Round copper wire for electrical purposes (the source text source-text extraction writes “CB/T 3953”, requires confirmation against the source standard (source-text extraction))
• GB/T 4756 Petroleum liquids — Manual sampling (GB/T 4756—1998, eqv ISO 3170:1988)
• GB/T 6682 Water for analytical laboratory use — Specification and test methods (GB/T 6682—1992, neq ISO 3696:1987)
• GB/T 12581 Determination of oxidation stability of inhibited mineral oils
• Explanation of normative references: For dated normative references, all subsequent amendments (excluding corrigenda) or revisions do not apply to this standard; however, parties to agreements based on this standard are encouraged to investigate whether the latest versions of these documents can be used; for undated normative references, the latest version applies to this standard.

13. Source and verification

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14. Quick Reference for Questions and Answers