SH/T 0185-1992 Determination of Oxidation Stability of Straight-run Lubricating Oils

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Card type: Test method

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

• Standard number: SH/T 0185-92
• Full name: Determination of Oxidation Stability of Straight-run Lubricating Oils
• English name: not provided in the available source
• Replacement relationship: replaces ZB E34 001-86
• Other: approved by 1992-05-20, implemented by 1992-05-20; (confirmed in 2000)
• Reference adoption: British Petroleum Institute standard IP 306/82 "Determination of Oxidation Stability of Straight-run Lubricating Oils"

2. Scope of application and non-applicability

• This standard specifies a method for determining the oxidation stability of straight-run lubricating oils.
• This standard applies to the determination of straight-run lubricating oils and lubricating oils without additives.
• Not applicable: not provided in the available source.

3. Method principle

Place two oxidation tubes containing the test sample (one without catalyst, the other with copper catalyst) into a heating bath at a temperature of 120℃ and pass oxygen through for 48h. Volatile acids are blown out by the flowing oxygen and absorbed by water. After oxidation is completed, the volatile acid value, soluble acid value, and sediment content in the oil need to be determined. Oxidation stability is expressed as the percentage of total oxidation products.

4. Reagents and materials (purity / preparation)

4.1 Materials

• 4.2.1 Copper catalyst: copper wire with purity of 99.9%, meeting the requirements of number 12 in GB 5231, diameter 1.03～1.05mm, length 770mm (or diameter 1.00～1.02mm, length 790mm).
• 4.2.2 Quantitative filter paper: medium speed (filtration speed 31～60s), diameter 11cm.
• 4.2.3 Oxygen: purity of 99.5% or above.
• 4.2.4 Emery cloth (sandpaper): grit number 150 or 180.
• 4.2.5 Fine yarn gloves.

4.2 Reagents

• 5.1 n-Heptane: analytical reagent.
• 5.2 Trichloromethane: analytical reagent.
• 5.3 Acetone: analytical reagent.
• 5.4 95% Ethanol: analytical reagent.
• 5.5 Toluene: analytical reagent.
• 5.6 Toluene-ethanol mixed liquid: prepared by mixing toluene and 95% ethanol in a volume ratio of 6:4.
• 5.7 Sulfuric acid: analytical reagent.
• 5.8 Potassium hydroxide: analytical reagent, prepared as c(KOH)=0.1 mol/L potassium hydroxide-ethanol standard titration solution.
• 5.9 Cobalt nitrate [Co(NO3)2·6H2O]: analytical reagent, prepared as 100g/L solution.
• 5.10 Hydrochloric acid: analytical reagent. Dilute 4.5mL hydrochloric acid with 95% ethanol to 1L to prepare hydrochloric acid solution.
• 5.11 Phenolphthalein indicator: prepared as 10g/L phenolphthalein-ethanol indicator solution.
• 5.12 Chromic acid cleaning solution.
• 5.13 Distilled water or ion-exchange water.
• 5.14 Alkaline blue 6B: prepared as 20g/L alkaline blue 6B- ethanol indicator solution. When preparing the solution, weigh alkaline blue 6B 2g, weighed accurately to 0.01g, then add it to 100mL boiling 95% ethanol, and reflux on a water bath for 1h. After cooling, filter, add 3mL hydrochloric acid solution, and after 24h perform acid value determination to check the sensitivity of the indicator, that is, there is an obvious color change from blue to red. If the red color is similar to the cobalt nitrate solution, the indicator sensitivity is good; if the sensitivity is insufficient, hydrochloric acid solution should be added again, and after 24h check again. Repeat this step until the sensitivity is acceptable.

5. Apparatus and equipment

• 4.1.1 Oxidation tube: made of heat-resistant hard glass (see Figure 1).
• 4.1.2 Absorption tube: the absorption tube is the same as the oxidation tube, and the two tubes are connected by a known elastic rubber tube (the distance between the central axes of the two tubes is 150mm±50mm). The absorption tube is installed outside the heating bath.
• 4.1.3 Heating bath: aluminum alloy block heating bath or oil bath, capable of automatically controlling the bath temperature so that the temperature of the test 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 tube). The oil in the test tube should be filled to the immersion line of the thermometer and placed in the heating bath.
  • For the aluminum alloy block heating bath, the upper surface temperature of the heating bath must be maintained at 60℃±5℃ (requires confirmation against the source standard (source-text extraction), the original text is "6090±5 9C"). This temperature is measured by a thermometer inserted into a drilled aluminum block (see Figure 2). Except for the upper surface of the heating bath, all surfaces of the aluminum block are protected by a suitable insulating layer. The oxidation tube is inserted into a hole with a total depth of 150mm. The hole depth of the heated part of the aluminum block is at least 125mm, and the metal short sleeve passing through the insulating cover and surrounding each oxidation tube can ensure that the oxidation tube is heated for a length of 150mm or more.
  • If an oil bath is used, the immersion depth of the oxidation tube in the oil is 137mm, and the total depth in the oil bath is 150mm. For both types of heating baths, the height of the oxidation tube exposed above the upper surface of the bath is 60mm. The diameter of the hole in the heating bath should be just enough to insert the oxidation tube. If it is loose, a O type gasket with a diameter of 25mm can be placed over the tube and pressed tightly against the surface of the heating bath.
• 4.1.4 Water bath.
• 4.1.5 Oxygen flow meter: 1.0L/h±0.1 L/h.
• 4.1.6 Oxygen flow control device.
• 4.1.7 Thermometer: 72～126℃, scale division value 0.2℃ (the thermometer range and scale division are garbled in the source transcription and require verification).
• 4.1.8 Glass funnel: diameter 60～70mm.
• 4.1.9 Wash bottle: 500mL.
• 4.1.10 Volumetric flask: 500mL.
• 4.1.11 Weighing bottle: bottle height 50mm, bottle diameter 30mm.
• 4.1.12 Stoppered conical flask: 500mL.
• 4.1.13 Conical flask: 100, 250, 500mL.
• 4.1.14 Microburette: 2mL, scale division value 0.01mL.
• 4.1.15 Soap film flow meter: 10mL, scale division value 0.5mL (requires confirmation against the source standard (source-text extraction), the original text is "IOML, scale division value O. SmL").

6. Recommended operating conditions

• Oxidation temperature: 120℃±0.5℃.
• Oxygen passage time: continuous oxidation for 48h.
• Oxygen flow rate: 1.0L/h±0.1 L/h (the flow rate must be checked daily).
• Upper surface temperature of aluminum alloy block heating bath: 60℃±5℃ (requires confirmation against the source standard (source-text extraction)).
• The absorption tube is filled with 25mL distilled water or ion-exchange water, and 5～6 drops of phenolphthalein-ethanol indicator solution are added.
• Standing conditions after oxidation: stand in the dark for 24h at 20℃±2℃.

7. Sampling and sample preparation

• 7.1 Weigh the test sample 25g±0.04g into two clean, dry oxidation tubes respectively, then place the copper catalyst coil into one of the oxidation tubes.
• 6.2 Preparation of copper catalyst coil: before use, wipe a copper wire of length 770 (or 790) mm first with a cotton gauze moistened with n-heptane, then rub with emery cloth or sandpaper until a fresh metal surface is exposed, and then wipe clean with clean, dry cotton gauze. After that, the metal wire must not be directly touched by hand. Clean gloves should be worn during operation. Wind the copper wire into a coil with an outer diameter of 20mm and a length of 50mm, and immediately store it in n-heptane for later use.
• 6.1 Cleaning the test tubes: the oxidation tube and absorption tube should be cleaned by chemical methods. A better method is to first wash with acetone, then with distilled water, drain, and soak in sulfuric acid for at least 16h, rinse with tap water until free of acid, and then rinse with distilled water. Dry the tubes in an oven at 105～110℃ for at least 3h, then take them out and place them in a desiccator to cool to room temperature for later use. Chromic acid cleaning solution can also be used instead of acetone and sulfuric acid to clean the test tubes.

8. Analysis procedure

• 7.1 Place the two oxidation tubes into a heating bath that can maintain the temperature of the test sample in the oxidation tubes at 120℃±0.5℃; fill the two absorption tubes respectively with 25mL distilled water or ion-exchange water, then add 5～6 drops of phenolphthalein-ethanol indicator solution, and connect the oxidation tubes and absorption tubes. To prevent water evaporation, the absorption tubes must be separated from the heating bath by a heat-insulating layer.
  • Note: The glass ground joints of the oxidation tubes are all sealed with 1 drops of test sample.
• 7.2 Turn on oxygen, adjust the oxygen flow rate to 1.0L/h±0.1 L/h (the flow rate must be checked daily), record the start time of oxidation, and continuously oxidize for 48h. During the oxidation period, the temperature must be maintained at 120℃±0.5℃.
• 7.3 After oxidation is completed, turn off the oxygen, remove the oxidation tubes and absorption tubes, take the oxidation tubes out of the heating bath and place them in the dark to cool, then pour all the oxidized oil into a 500mL stoppered conical flask. Wash the oxidation tubes, oxygen conduits, and copper catalyst coils respectively with 300mL n-heptane until there is no oil trace, combine the n-heptane washings into the same stoppered conical flask, and let stand in the dark for 24h at 20℃±2℃.
• 7.4 Determination of volatile acid value: remove the absorption tube containing water and phenolphthalein-ethanol indicator solution, pour all the liquid in the absorption tube into a 250mL conical flask, rinse the absorption tube with distilled water, and pour the washings into the same conical flask. Titrate the volatile acid value with [c(KOH)=0.1mol/L] potassium hydroxide-ethanol standard titration solution, and perform a blank test.
• 7.5 Determination of sediment content in oxidized oil: filter the oxidized oil and n-heptane mixture after standing for 24h through filter paper in a weighed weighing bottle into a 500mL volumetric flask, and wash the stoppered conical flask containing the settled mixture and the sediment on the filter paper with 150mL n-heptane until the filter paper has no oil trace. Place the filter paper with sediment into the weighed weighing bottle, place in an oven at 105～110℃, and dry to constant weight. Combine the filtrate into the 500mL volumetric flask and dilute to the mark for acid value determination. Dissolve all sediments adhering to the stoppered conical flask containing the settled mixture, oxidation tubes, oxygen conduits, and copper catalyst coils with 30mL trichloromethane into a weighed 100mL conical flask. Evaporate the trichloromethane in the conical flask completely on a water bath, then place in an oven at 105～110℃ and dry to constant weight.
• 7.6 Determination of soluble acid value: before use, neutralize the titration solvent as follows. Into a 250mL conical flask, inject 100mL toluene-ethanol mixed liquid and 2mL alkaline blue 6B- ethanol indicator solution, neutralize with [c(KOH)=0.1 mol/L] potassium hydroxide-ethanol standard titration solution so that the resulting red color can be compared with 100g/L cobalt nitrate solution (that is, the blue color disappears and the red color just appears), and keep it from fading for 15s.
  • After uniformly shaking the mixture of oxidized oil and n-heptane placed in a 500mL volumetric flask, take 100mL and pour it into a 250mL conical flask, add the above neutralized titration solvent while continuously shaking, then titrate with [c(KOH)=0.1mol/L] potassium hydroxide-ethanol standard titration solution at a temperature below 30℃, measure three times in total, and take the average as the result.
  • Note: In general, only one measurement may be made; for arbitration, three measurements should be made.
• 7.7 The volatile acid value, soluble acid value, and precipitate content in the oxidized oil of each sample should be determined by repeated tests.

9. Qualitative and Quantitative Determination and Calculation Formulas

• 8.1 Volatile acid value X1 (mgKOH/g) is calculated according to formula (1): X1 = (V - Vc) × 0.0561 × c × 1000 / 25 Where: V— volume of potassium hydroxide-ethanol standard titration solution consumed in titrating the volatile acid value, mL; Vc— volume of potassium hydroxide-ethanol standard titration solution consumed in the blank test, mL; c— actual concentration of the potassium hydroxide-ethanol standard titration solution, mol/L; 0.0561— mass of volatile acid (expressed as potassium hydroxide) in grams equivalent to 1.00mL potassium hydroxide-ethanol standard titration solution [c(KOH)=1.000mol/L]; 25— mass of the sample, g.
• 8.2 Precipitate content in oxidized oil X2% (m/m) is calculated according to formula (2): X2 = (a + b) × 4 Where: a— mass of precipitate insoluble in n-heptane, g; b— mass of precipitate recovered from chloroform, g.
• 8.3 Soluble acid value X3 (mgKOH/g) is calculated according to formula (3): X3 = V1 × 0.0561 × c × 1000 / 25 (requires confirmation against the source standard (source-text extraction), no clear value is seen at the denominator in the source text, only “V, x 0.0561 x c x 1000” is seen) Where: V1— volume of potassium hydroxide-ethanol standard titration solution consumed in titrating the soluble acid value, mL; c— actual concentration of the potassium hydroxide-ethanol standard titration solution, mol/L; 0.0561— mass of soluble acid (expressed as potassium hydroxide) in grams equivalent to 1.00mL potassium hydroxide-ethanol standard titration solution [c(KOH)=1.000mol/L].
• 8.4 Total oxidation products TOP[% (m/m)] is calculated according to formula (4): TOP = X2 + 180(X1 + X3) / 561 Where: X1— volatile acid value, mgKOH/g; X2— precipitate content in oxidized oil, % (m/m); X3— soluble acid value, mgKOH/g; 180— average molecular weight of the acid after oil oxidation.

10. Precision

The following provisions are used to judge the reliability of test results (95% confidence level).

• 9.1 Repeatability: The difference between two results obtained by the same operator in repeated determinations shall not exceed the value in the table below.
• 9.2 Reproducibility: The difference between two results submitted by two laboratories shall not exceed the value in the table below.

Precision table:

Note: X represents the average of two results.

11. Report

Take the arithmetic mean of two results from repeated determinations as the total oxidation products of the sample without catalyst and with copper catalyst, and the ratio of precipitate to total oxidation products with copper catalyst.

• 10.1 According to this standard, the total oxidation products without catalyst or with copper catalyst are expressed as mass percentage; report results to two decimal places, accurate to 0.01% (m/m).
• 10.2 The ratio of precipitate to total oxidation products with copper catalyst is expressed as a percentage; report data as integers.

12. Referenced Documents

• GB 5231 Wrought copper — Chemical composition and product forms
• Editor's note: The standard numbers and standard names of the referenced standards in this standard have changed as follows:
  • Original standard number: GB 5231
  • Current standard number: GB/T 5231
  • Current standard name: Wrought copper and copper alloys — Chemical composition and product forms

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.

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