SH/T 0124-2000 Determination of oxidation stability of turbine oils containing antioxidants

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Standard number: SH/T 0124-2000
• Chinese name: Determination of oxidation stability of turbine oils containing antioxidants
• English name: Determination of oxidation stability of inhibited turbine oils
• Replacement relationship: replaces SH/T 0124-1992
• Adoption relationship: equivalent adoption of the British Petroleum Institute standard IP 280/96 "Petroleum products and lubricants—Determination of oxidation stability of mineral turbine oils containing antioxidants"
• Publication/implementation: approved by the State Bureau of Petroleum and Chemical Industry 2000-11-27, implemented on 2001-05-01
• First publication: 1992 year
• Drafting unit: Lanzhou Refining and Chemical Branch of PetroChina Company Limited
• Main drafter: Xiong Chao
• Custodian: Sinopec Research Institute of Petroleum Processing
• Proposed by: Sinopec Corp.

2. Scope of application and non-applicability

• Applicable to the determination of the oxidation resistance of unused mineral turbine oils containing antioxidants.
• Also applicable to other types of oils, such as hydraulic system oils.
• Note: This method can also be used for petroleum product specifications; the measured values can be used in the laboratory to evaluate the oxidation stability of turbine oils. However, attention should be paid to the difference between the oxidation stability of an oil measured by a single method and the oxidation stability of the oil under actual working conditions.
• Not applicable: no explicit non-applicable clause is provided in the available source.

3. Method principle

Place the oxidation tube containing the test sample (to which oil-soluble iron naphthenate and copper naphthenate catalysts have been added) into a heating bath at a temperature of 120℃ and pass oxygen through for 164h. After the test is completed, determine the volatile acid value, soluble acid value, and sludge content. If it is necessary to determine the time at which the evolution rate of volatile acids reaches a significant increase (induction period), the volatile acid value may be determined daily, and an acid value-time curve may be plotted to determine it.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 5.1 n-Heptane: analytical reagent.
• 5.2 Dichloromethane: analytical reagent.
• 5.3 Toluene: analytical reagent.
• 5.4 95% Ethanol: analytical reagent.
• 5.5 Toluene-ethanol mixed solution: prepared from toluene and 95% ethanol in a volume ratio of 6:4.
• 5.6 Hydrochloric acid: analytical reagent. Dilute with water to a c(HCl)=0.1mol/L solution.
• 5.7 Potassium hydroxide: analytical reagent. Prepare a c(KOH)=0.1mol/L potassium hydroxide-ethanol standard titration solution. Standardize daily or periodically.
• 5.8 Cobalt nitrate [Co(NO3)2·6H2O]: analytical reagent. Prepare a 10%(m/m) solution.
• 5.9 Alkali blue: prepare an alkali blue 6B— ethanol indicator solution with a concentration of 20g/L. In order for the alkali blue 6B indicator to give a good titration endpoint, after it is dissolved in ethanol, add hydrochloric acid at a ratio of 0.03mL per milliliter of indicator solution. After 24h, perform an acid value test to determine its sensitivity. That is, if it changes distinctly from blue to red, comparable to the color of a 10% cobalt nitrate [Co(NO3)2·6H2O] solution, then the indicator solution has good sensitivity; if the sensitivity is insufficient, hydrochloric acid solution should be added again, and the test should be performed again after 24h, repeating this step until the sensitivity is acceptable.
• 5.10 Phenolphthalein: prepare a 10g/L phenolphthalein-ethanol indicator solution.
• 5.11 Acetone: analytical reagent.
• 5.12 Distilled water or deionized water: meets the requirements for GB/T 6682 grade two water.
• 5.13 Sulfuric acid: not less than 98%(m/m).

4.2 Materials

• 4.2.1 Oxygen: purity of 99.4% or above; the oxygen must be dried with a suitable desiccant, and the oxygen delivery system should ensure that oxygen is fed smoothly into the measuring equipment. At the start of each experiment, the oxygen flow rate is given by the measuring equipment and should be set at 1.0L/h ± 0.1L/h, and verified daily with a soap film flowmeter.
  • Note: The oxygen equipment used must be carefully freed of oil, grease, and other combustible substances. Do not use oil or grease on regulators, valves, or controls. If a line leak is suspected, immediately shut off the oxygen and inspect. Depressurize the line before inspection. The oxygen supply system should be inspected regularly.
• 4.2.2 Catalysts
  • 4.2.2.1 Copper naphthenate solution containing 1%(m/m) copper.
  • 4.2.2.2 Iron naphthenate solution containing 1%(m/m) iron.
  • The above 1%(m/m) solutions are obtained by diluting a mother liquor conforming to Appendix A. The total content of other metal ions (except sodium) in the resulting solution is not greater than 300mg/ tons; the diluent used is a turbine oil base oil of viscosity grade ISO 32 produced from non-paraffinic mineral oil. The solution should be stored protected from light.

5. Apparatus and equipment

• 4.1.1 Oxidation tube: made of borosilicate glass or neutral glass conforming to the dimensions in Figure 1.
• 4.1.2 Absorption tube: same as the oxidation tube; the distance between the center axes of the two tubes is 150mm±50mm; the two tubes are connected with as short a silicone rubber tube as possible; the absorption tube is fixed outside the heating bath.
• 4.1.3 Heating bath: aluminum alloy heating bath (see Figure 2) or oil bath, capable of automatically controlling temperature so that the temperature of the sample in the oxidation tube is maintained at 120℃±0.5℃; the temperature is measured by a thermometer inserted into a test tube containing the sample (the thermometer is 5mm from the bottom of the test tube). The sample in the test tube should be filled to the immersion line of the thermometer and placed in the heating bath. The upper surface of the heating bath should be maintained at 90℃±5℃ (requires confirmation against the source standard (source-text extraction); the source text here is "[unreadable value]℃±5'C"), in order to eliminate the slight influence of ambient temperature changes on the determination results. This temperature is measured by a thermometer installed in an aluminum block drilled with a hole. Except for the face in contact with the upper surface of the heating bath, all other faces of the block must be protected with insulating material. The block should be as close as possible to the hole in the heating bath used for inserting the test tube, and within the area of the aluminum alloy heating block.
  • When using an aluminum alloy heating bath, the oxidation tube is inserted into a hole with a total depth of 150mm. The hole depth in the aluminum alloy heating block portion is at least 125mm; a metal ring passing through the insulating cover and surrounding each oxidation tube causes a length of 150mm of the oxidation tube to be heated. When using an oil bath, the immersion depth of the oxidation tube in the oil bath is 137mm, and the total depth is 150mm. For both types of heating baths, the length of the oxidation tube above the upper surface of the heating bath is 60mm; the diameter of the hole is just sufficient to insert the oxidation tube; if loose, a O type ring with a diameter of 25mm may be placed over the tube and pressed tightly against the heating bath surface.
• 4.1.4 Filtration membrane: pore size 5μm, diameter 47mm, matching the liquid to be tested.
• 4.1.5 Stoppered conical flask: 500mL.
• 4.1.6 Soap film flowmeter: used to check the oxygen flow rate; typical components are shown in Figure 3.
• 4.1.7 Microburette: graduation value 0.01mL.
• 4.1.8 Thermometer: meets the requirements of GB/T 514 for turbine oil oxidation 2 number, or a temperature measuring device of equivalent accuracy and suitable range.
• 4.1.9 Oven: capable of controlling temperature at 75℃±5℃, 110℃±5℃.
• 4.1.10 Filtration equipment: used for membrane filtration, minimum capacity 1L.
• 4.1.11 Conical flask: 100mL, 250mL, 500mL.
• 4.1.12 Volumetric flask: 500mL.
• 4.1.13 Beaker: 100mL.
• 4.1.14 Pipette: 100mL.
• 4.1.15 Water bath.

6. Recommended operating conditions

• Oxidation temperature: 120℃±0.5℃.
• Upper surface temperature of heating bath: 90℃±5℃ (requires confirmation against the source standard (source-text extraction)).
• Oxygen purity: ≥99.4%.
• Oxygen flow rate: 1.0L/h ± 0.1L/h, verified daily with a soap film flowmeter.
• Oxidation time: continuous oxidation for 164h (when the induction period is not required to be determined).
• Standing of oxidized oil: stand at room temperature protected from light for not less than 16h.
• Drying of filtration membrane: dry at 80℃ for 1h (7.4.2); for the arbitration method, dry the filter funnel at 100℃ for 1h (B3.1).
• Drying of sludge: dry at 75℃±5℃ for 1h (7.4.2 filter membrane); dry at 110℃±5℃ for 1h (7.4.2 sludge recovered with dichloromethane and B3.3).
• Cleaning and drying of test tubes: dry in an oven at 110℃±5℃ for not less than 3h (Chapter 6).
• Heating the sample to dissolve the catalyst: temperature not exceeding 80℃, gentle heating for not more than 5min.

7. Sampling and sample preparation

• 7.1 In a beaker of 100mL, separately weigh 60mg±0.4mg copper naphthenate containing 1%(m/m) copper and iron naphthenate containing 1%(m/m) iron, and weigh 30g±0.04g sample, so that the copper content and iron content in the sample are both 20mg/kg±0.5mg/kg. Then place the beaker in an oven at a temperature not exceeding 80℃ and gently heat the sample for not more than 5min. After the catalyst has dissolved, remove from the oven and cool to room temperature, and weigh 25g±0.04g of the sample from the beaker into the oxidation tube, and seal the ground joint of the oxidation tube with one drop of the sample to be tested.
• Test tube cleaning (Chapter 6): first wash the oxidation tube and absorption tube with acetone, then rinse with tap water, drain, and immerse in concentrated sulfuric acid for not less than 16h. After removal from the sulfuric acid, first rinse with tap water until free of acid, then rinse with distilled water, place in an oven at a temperature of 110℃±5℃ and dry for not less than 3h, then remove and place in a desiccator to cool to room temperature for later use.

8. Analytical procedure

8.1 Oxidation test (7.1)

Place the oxidation tube into a heating bath at a temperature of 120℃±0.5℃. Add 25mL water and 5～6 drops of phenolphthalein-ethanol indicator solution to the absorption tube, and connect the oxidation tube and the absorption tube. To avoid evaporation of water in the absorption tube, it must be separated from the heating bath with insulating material. Turn on the oxygen and adjust the oxygen flow rate to 1.0L/h±0.1L/h (this flow rate must be verified daily). Record the time when oxidation begins; during oxidation, 120℃±0.5℃ must be maintained. If the induction period is not required to be determined, oxidize continuously for 164h. After oxidation is completed, turn off the oxygen, disconnect the oxidation tube and absorption tube, remove the oxidation tube from the heating bath, cool in a dark place for about 1h, then transfer the oxidized oil into a stoppered conical flask of 500mL, and separately wash the oxidation tube and the oxygen inlet tube with 300mL n-heptane until free of oil traces. Combine the n-heptane washings into the same stoppered conical flask. Allow to stand at room temperature protected from light for not less than 16h.

8.2 Determination of volatile acid value (7.2)

Remove the absorption tube containing water and phenolphthalein-ethanol indicator solution, pour all the liquid in the absorption tube into the conical flask of 250mL, and rinse the absorption tube with 25mL distilled water, pour the washing liquid together into the same conical flask, titrate the volatile acid with 0.1mol/L potassium hydroxide-ethanol standard titration solution, and record the volume of potassium hydroxide-ethanol standard titration solution consumed V1(mL). The above steps should be carried out as soon as possible after the oxidation is completed, and during titration should be as fast as possible.

8.3 Determination of induction period (7.3)

If the determination of the induction period is required, remove the absorption tube containing distilled water and phenolphthalein-ethanol indicator solution on time every day, and at the same time, place another absorption tube containing the same distilled water and phenolphthalein-ethanol indicator solution in the original position. Titrate the volatile acid in the removed absorption tube with 0.1mol/L potassium hydroxide-ethanol standard titration solution according to the method of clause 7.2, and draw an acid value-time curve based on the volatile acid value measured daily. The interval between two determinations may also be appropriately arranged to obtain a continuous acid value-time curve.

8.4 Determination of sludge content (7.4)

• 7.4.1 In arbitration tests, the determination of sludge content shall be carried out according to Appendix B; for routine determination, the sludge content may be determined according to the procedure of 7.4.2.
• 7.4.2 Filter the oxidized oil/n-heptane mixture that has been left for 16h through a filter membrane, the filter membrane having been previously dried at 80℃ for 1h and weighed to the nearest 0.1mg. If the filtrate is turbid, it must be refiltered through the same filter membrane until clear and transparent. Carefully rinse the stoppered flask and the sludge on the filter membrane repeatedly with a total amount of no more than 150mL n-heptane until no oil traces remain. Under vacuum, carefully remove the clamp and liquid reservoir cup from the filter, and gently rinse the surface of the filter membrane from the periphery to the center with a small amount of n-heptane, taking care not to wash away the sludge on the membrane surface; after rinsing, maintain vacuum for a few seconds to remove residual n-heptane. Retain the filtrate and rinse liquid for determination of soluble acid value, carefully remove the filter membrane, dry at 75℃±5℃ for 1h, and weigh to the nearest 0.1mg. The sludge mass obtained is recorded as m1.
• Dissolve the sludge adhering to the oxidation tube and oxygen inlet tube with a total amount of 30mL dichloromethane, transfer the solution to a constant-weight 100mL conical flask, evaporate the dichloromethane on a heated water bath, then dry in an oven at 110℃±5℃ for 1h, cool to room temperature and weigh to the nearest 0.1mg. The sludge mass obtained is recorded as m2.

8.5 Determination of soluble acid value (7.5)

Collect the above filtrate and washing liquid into a 500mL volumetric flask, dilute to the mark with n-heptane, shake uniformly and set aside. In a 500mL conical flask, add 100mL toluene-ethanol mixed solvent and 2mL alkaline blue 6B— ethanol indicator solution, titrate with 0.1mol/L potassium hydroxide-ethanol standard titration solution, with the endpoint being when the titrated liquid shows a color comparable to the red color of 10%(m/m) cobalt nitrate solution and maintains it for at least 15s. Use a 100mL pipette to draw 100mL oxidized oil/n-heptane solution from the volumetric flask into the above 500mL conical flask, titrate with 0.1mol/L potassium hydroxide-ethanol standard titration solution at an ambient temperature not higher than 30℃, with the endpoint being when the titrated liquid shows a color comparable to the red color of 10%(m/m) cobalt nitrate solution and maintains it for at least 15s. Perform three determinations and take the average as the volume of potassium hydroxide-ethanol standard titration solution consumed V2(mL). When the oxidized oil is very dark, the sampling amount of oxidized oil/n-heptane solution may be appropriately reduced to facilitate observation of the endpoint. The volume taken is recorded as V3.

• Note: When some oxidized oils are dark in color, making it difficult to observe the titration endpoint where the titrated liquid matches the red color of 10%(m/m) cobalt nitrate solution, the endpoint may also be taken as the disappearance of the blue color of the titrated liquid and no reappearance of blue within 15s. At the same time, the blank titration endpoint of the toluene-ethanol mixed solvent should be kept consistent with this.

8.6 Appendix B Arbitration determination method for sludge content

• B1 Scope: This appendix provides another determination method for determining the sludge content in the oxidized oil/n-heptane mixture in 7.4.2, which is used for arbitration tests.
• B2 Apparatus: All other equipment in 4.1 except 4.1.4. Filter funnel, a sintered glass filter funnel with a pore size conforming to grade P10 specified in GB/T 11415.
• B3.1 Filter the oxidized oil/n-heptane mixture that has been left for 16h through a filter funnel, the filter funnel having been previously dried at 100℃ for 1h and weighed to the nearest 0.1mg. If the filtrate is turbid, it must be refiltered through the same filter funnel until clear and transparent.
• B3.2 Carefully rinse the sludge repeatedly with a total amount of no more than 150mL n-heptane until no oil traces remain. Retain the filtrate and rinse liquid for determination of soluble acid value. Dry the filter funnel in an oven at 110℃±5℃ for 1h, and weigh to the nearest 0.1mg. The sludge mass obtained is recorded as m1.
• B3.3 Dissolve the sludge adhering to the oxidation tube and oxygen inlet tube with a total amount of 30mL dichloromethane, transfer the solution to a constant-weight 100mL conical flask, heat on a water bath to evaporate the dichloromethane. Then dry in an oven at 110℃±5℃ for 1h. Cool to room temperature and weigh to the nearest 0.1mg. The sludge mass obtained is recorded as m2.
• B3.4 Calculate the total sludge content according to clause 8.2.

9. Qualitative and quantitative and calculation formulas

• 8.1 Volatile acid value X1(mgKOH/g) is calculated according to formula (1): X1 = V1 × c × 0.0561 × 1000 / 25 Where: V1— volume of potassium hydroxide-ethanol standard titration solution consumed when titrating volatile acid, mL; c— actual concentration of potassium hydroxide-ethanol standard titration solution, mol/L; 25— mass of sample, g; 0.0561— mass of volatile acid (expressed as potassium hydroxide) in grams equivalent to 1.000mol potassium hydroxide-ethanol standard titration solution c(KOH)=1.000mol/L.
• 8.2 Total sludge content D[%(m/m)] is calculated according to formula (2): D = 4(m1 + m2) Where: m1— mass of sludge insoluble in n-heptane, g; m2— mass of sludge recovered by dichloromethane, g; 4— coefficient for converting percentage.
• 8.3 Soluble acid value X2(mgKOH/g) is calculated according to formula (3): X2 = V2 × 0.0561 × c × 1000 / (25 × V3/500) Where: V2— volume of potassium hydroxide-ethanol standard titration solution consumed to neutralize the oxidized oil/n-heptane solution, mL; c— actual concentration of potassium hydroxide-ethanol standard titration solution, mol/L; V3— volume of oxidized oil/n-heptane solution actually taken, mL; 25— mass of sample, g; 500— volume of oxidized oil after dilution with n-heptane.
• 8.4 Total acid value X(mgKOH/g) is calculated according to formula (4): X = X1 + X2
• 8.5 Total oxidation products TOP[%(m/m)] is calculated according to formula (5): TOP = D + 180X/561 Where: D— total sludge content; X— total acid value; 180— average relative molar mass of oxidized acidic products in grams per mole; 561— 10 times the molar mass of potassium hydroxide in grams per mole.

10. Precision

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

• 9.1 Repeatability: The difference between two results of repeated determinations by the same operator on the same sample shall not exceed the data listed in Table 1.
• 9.2 Reproducibility: The difference between two results submitted by different laboratories for the same sample shall not exceed the data listed in Table 1.

Table 1 Precision table

x is the average of two determination results. Note: The precision of typical x values is listed in Table 2, Table 3 and Table 4. These precision data are results from determinations of oil samples with total acid value in the range 0.5～10mgKOH/g, total sludge content in the range 0.03%(m/m)～3%(m/m), and total oxidation products in the range 0.25%(m/m)～5.7%(m/m).

Table 2 Typical precision data for total acid value (mgKOH/g)

Table 3 Typical precision data for total sludge content %(m/m)

Table 4 Typical precision data for total oxidation products %(m/m)

11. Report

Report the total acid number of the sample to the nearest 0.01mgKOH/g; report the total sludge content and total oxidation products to the nearest 0.01%(m/m); report the ratio of total sludge content to total oxidation products to the nearest integer.

12. Normative references

• GB/T 514 Specification for liquid-in-glass thermometers for testing petroleum products
• GB/T 3141 Industrial liquid lubricants ISO Viscosity classification
• GB/T 6682 Water for analytical laboratory use — Specification and test methods
• GB/T 11415 Laboratory sintered (fritted) filters — Porosity grading, classification and designation

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