SH/T 0259-1992 Determination of thermal oxidation stability of lubricating oils

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 title / English name / replacement relationship

• Standard number: SH/T 0259-92
• Full title: Determination of thermal oxidation stability of lubricating oils
• English name: not provided in the available source
• Replacement relationship: replaces SY 2618-66(82)
• Other: confirmed in 2004; approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies a method for evaluating the tendency of lubricating oils to form lacquer-like deposits on engine parts (near the piston rings) and the effectiveness of additives in reducing lacquer-like deposits.
• This standard applies to lubricating oils.
• Not applicable: not provided in the available source.

3. Method principle

At a specified temperature, a thin layer of lubricating oil is oxidized on a metal surface, and the time required to form an oily residue composed of 50% working fraction and 50% lacquer-like deposits is measured.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 4.1 Sodium hydroxide: chemically pure, prepared as a 100 g/L solution, used to remove lacquer-like deposits on the evaporation dishes. (The source text reads “100[unreadable unit]L”, suspected to be 100 g/L, requires confirmation against the source standard (source-text extraction))
• 4.2 Hydrochloric acid: chemically pure.
• 4.3 Distilled water.
• 4.4 Benzene: chemically pure.
• 4.5 95% Ethanol: chemically pure.
• 4.6 Ethanol-benzene mixed liquid: prepared from 95% ethanol and benzene in a volume ratio of 1:4.
• 4.7 n-Heptane: distillation range 96～102 ℃ (the source text reads “%[unreadable separator]1029C”, requires confirmation against the source standard (source-text extraction)), free of aromatic hydrocarbons.

4.2 Materials

• 3.2.1 Industrial filter paper.
• 3.2.2 Emery cloth (or emery paper): grit size 180 or 240.
• 3.2.3 Emery: grit size 220.
• 3.2.4 Alloy: melting point not exceeding 230 ℃.
• 3.2.5 Straight-run light gasoline.

5. Apparatus and equipment

• 3.1.1 Lacquer deposit former (see Figure 1): composed of an upwardly open metal cylinder 2, with a movable thermocouple 1 on the side curve, a heating plate 6, an electric heater 5 (which should be able to heat the steel block and evaporation dish to 350 ℃), and a pull rod 7 with a handle 9. Its pull rod, by the force of spring 8, presses the steel block 3 tightly against the heating plate 6; round holes 4 are provided around the lower part of the cylinder to allow air to enter the lacquer deposit former freely. (The source text “[garbled side/cylinder description]p1[movable-part wording unreadable]1[garbled heating wording]6” is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• 3.1.2 Steel block: diameter 70 or 100 mm, thickness 10～10.2 mm, with a recess for inserting a thermometer on one face of the steel block; the distance from the center of this recess to the center of the steel block is 27 mm±0.2 mm, the diameter of the recess is 10 mm, and the depth is 6.4 mm±0.1 mm.
• 3.1.3 Evaporation dish (see Figure 2): made of steel, outer diameter 22～22.1 mm, rim height 1.0 mm±0.1 mm, rim wall thickness 0.3 mm, dish bottom thickness 1.0 mm±0.1 mm, with a number engraved on the outer surface.
• 3.1.4 Glass pipette (see Figure 3): with an elongated tip, used to accurately draw the sample amount.
• 3.1.5 Metal stand (see Figure 4): used for holding the pipette.
• 3.1.6 Remover (see Figure 5): used for removing the evaporation dish from the steel block.
• 3.1.7 Temperature regulator: use an autotransformer or rheostat to regulate the temperature of the heating plate of the lacquer deposit former.
• 3.1.8 Stopwatch.
• 3.1.9 Porcelain cup: used for washing the evaporation dish.
• 3.1.10 Glass mercury thermometer: 0～360 ℃, scale division value 1 ℃, immersion depth 45 mm, mercury bulb length 6～7.5 mm. (The source text “0[unreadable separator]360`C, division value 19c” requires confirmation against the source standard (source-text extraction))
• 3.1.11 Glass plate: used for grinding and wiping the steel block and evaporation dish.
• 3.1.12 Ceramic plate.
• 3.1.13 Extraction apparatus: with a 250 or 500 mL flask.
• 3.1.14 Metal stand (see Figure 6): length equivalent to the height of the extraction cylinder on the extraction apparatus.
• 3.1.15 Electric hot plate.
• 3.1.16 Desiccator.
• 3.1.17 Oven: capable of maintaining a constant temperature at 100～105 ℃.

6. Recommended operating conditions

• Test temperature: the temperature specified in the product standard, maintained constant; throughout the test, the temperature shall be maintained accurate to ±1 ℃ of the test control temperature.
• After the steel block reaches the specified temperature, hold for 3～5 min.
• Sample amount: 0.038～0.040 g.
• Extraction reflux condensate rate: 3～5 drops per second.
• Drying conditions: maintain at 100 ℃±1 ℃ for 1 h.

7. Sampling and sample preparation

• 5.3 The pipette must be calibrated. The calibration conditions shall be the same as the test conditions. The calibration method is to drip several portions of lubricating oil from the pipette, each portion about 4 drops, weighed accurately to 0.0004 g, and calculate the number of drops corresponding to each sample amount of 0.038～0.040 g. Before analyzing each new sample, recalibrate the pipette according to the above method.
• 5.4 Before the test, use a level to check the horizontal position of the heating plate of the thermostat.
• Other sampling requirements: not provided in the available source.

8. Analysis procedure

• 5.1 Before the test, the evaporation dish shall be clean and dry. If lacquer-like deposits adhere to the surface of the evaporation dish due to use, the evaporation dish must be boiled in sodium hydroxide solution for 15～20 min. After treatment with sodium hydroxide solution, wash carefully with water; any lacquer-like deposits not washed off shall be carefully scraped off with a scraper. The evaporation dish may also be soaked in ethanol-benzene mixed liquid. Then use tweezers to pick up cotton and wipe the lacquer-like deposits on the evaporation dish clean in the ethanol-benzene mixed liquid. Then immerse the evaporation dish in hydrochloric acid for 1～2 min, pour off the hydrochloric acid, quickly immerse the evaporation dish in water, rinse carefully with water while stirring, and then wipe the evaporation dish dry. Grind the evaporation dish clean with emery cloth, or grind with a small motor as follows: fit a rubber stopper with a diameter equal to the inner diameter of the evaporation dish onto the motor shaft, and attach cut emery cloth to the top of the stopper; when grinding the inner surface of the evaporation dish, press it intermittently against the rotating rubber stopper with emery cloth; when grinding the outer surface of the evaporation dish, press it gently against the rotating rubber stopper with emery cloth. Wipe the evaporation dish clean with clean emery cloth and place it under 100 ℃±1 ℃ to dry, cool, and weigh until the difference between two consecutive weighings is not greater than 0.0004 g.
• 5.2 The steel block is placed on one side of the heating plate; the surface must be clean and polished so that all points on the steel block can be heated uniformly. If lacquer-like deposits are occasionally found on the steel block, remove them immediately and polish the steel block with emery cloth or emery. The upper surface of the steel block shall be ground until the finish is such that no visible streaks can be seen with the naked eye.
• 6.1 Place the steel block on the heating plate of the thermostat and secure it with the pull rod (see Figure 1). Place 4～6 evaporation dishes, previously weighed accurately to 0.0002 g, symmetrically on the steel block; each evaporation dish must be 3～4 mm from the edge of the steel block. Then heat the thermostat. After the metal in the recess of the steel block melts, insert the thermometer into it so that the mercury bulb of the thermometer is completely immersed in the molten metal.
• 6.2 When the temperature reaches the temperature specified in the product standard, maintain constant temperature. The steel block is held at this temperature for 3～5 min. Then drip 0.038～0.040 g of sample cyclically into the evaporation dishes from above the thermostat. When half of the sample has been dripped in, start the stopwatch as the test start time. Throughout the test, maintain the temperature accurate to ±1 ℃ of the test control temperature.
• 6.3 During the test, when the lubricating oil in the evaporation dish is first seen to be oxidized and the oil film changes, remove one evaporation dish and record the removal time. Thereafter, for lubricating oils without additives, remove one evaporation dish every 3～5 min; for lubricating oils with additives, remove one evaporation dish every 5～10 min; place the evaporation dishes in a desiccator, cool to room temperature, and then weigh; weigh each evaporation dish accurately to 0.0002 g.
• 6.4 Place each of the above evaporation dishes containing lacquer-like deposits on the shelves of the metal stand (see Figure 6). One stand can hold 4～24 evaporation dishes. If the appearance of the residue has no liquid film and is in a broken state, each evaporation dish may be placed in a small envelope made of filter paper and then placed on the stand.
• 6.5 Connect the extraction cylinder of the extraction apparatus to the flask installed on the water bath or electric furnace, and add n-heptane to the extraction cylinder up to the top of the siphon tube; after all the n-heptane has flowed into the flask, add more n-heptane to one-half of the siphon tube.
• 6.6 Place the stand with the evaporation dishes into the extraction cylinder, connect the extraction cylinder to the condenser, and pass water through the condenser. Check whether the connections of all parts of the apparatus are tight and whether the apparatus is firmly fixed on the stand, then heat. The heating intensity shall keep the reflux condensate of the condenser at 3～5 drops per second. Continue extraction in this way until a completely transparent solution is obtained in the extraction cylinder; when n-heptane begins to flow from the siphon tube of the extraction cylinder into the flask again, stop heating. Then cool the flask, remove the condenser, and carefully take the stand with the evaporation dishes out of the extraction cylinder.
• 6.7 Place the evaporation dish on filter paper and move it into the oven, maintaining at 100 ℃±1 ℃ for 1 h. Remove the evaporation dish, cool to room temperature, and weigh, weighing to an accuracy of 0.0002 g; then repeat drying and weighing the evaporation dish until the difference between two consecutive weighings is not greater than 0.0004 g. Based on the weighing results, calculate the working fraction and lacquer-like substance of the lubricating oil, and then determine the thermal oxidation stability and lacquer formation coefficient.

9. Qualitative and Quantitative and Calculation Formulas

• 7.1 At temperature T and heating time t, the percentage of working fraction of lubricating oil in each evaporation dish G_T[% (m/m)] is calculated according to formula (1):

  G_T = [(m - m1) / m] × 100 …… (1)

  Where:

  • m —— mass of lubricating oil sample added to the evaporation dish, g;
  • m1 —— mass of evaporation dish and oily residue, g;
  • m2 —— mass of evaporation dish and lacquer-like residue, g.

  (Note: In the original formula (1), there is source-text extraction inconsistency between symbols and explanations, and the position of m2 in formula (1) requires confirmation (source-text extraction))

• 7.2 At temperature T and heating time t, the percentage of lacquer-like substance of lubricating oil in each evaporation dish Q_T[% (m/m)] is calculated according to formula (2):

  Q_T = [(m2 - m3) / m] × 100 …… (2)

  Where:

  • m3 —— mass of clean evaporation dish before test, g.

• 7.3 Calculate thermal oxidation stability according to the following method, expressed as t. On the ordinate axis, represent the working fraction percentage G_T and lacquer-like substance percentage Q_T at different test times in the same proportion, and record the corresponding test times on the abscissa axis [t(min)]. Then draw a relationship diagram of working fraction and lacquer-like substance versus test time. The intersection of the two curves on the diagram corresponds to the oily residue composed of 50% working fraction and 50% lacquer-like substance. Therefore, the test time corresponding to the intersection is the thermal oxidation stability test result of the lubricating oil (Figure 7).

• 7.4 The sum of the percentages corresponding to the intersection of the two curves G_T and Q_T on the ordinate axis (G_T + Q_T) is the value of the oily residue corresponding to thermal oxidation stability of t, because at the intersection G_T and Q_T are numerically equal to each other, so the value of the oily residue can also be expressed as 2Q_T.

  The lacquer formation coefficient Cv used to evaluate the tendency of thin-layer lubricating oil to change into lacquer-like residue due to oxidation is calculated according to formula (3):

  Cv = (G_T + Q_T) / (2Q_T) = G_T / Q_T …… (3)

  Where:

  • Q_T —— percentage of lacquer-like substance generated at temperature T and heating time t, % (m/m);
  • t —— thermal oxidation stability of the sample, min;
  • G_T —— percentage of working fraction at temperature T and heating time t, % (m/m).

  (Note: The original formula (3) and symbol explanations contain source-text extraction noise, requires confirmation (source-text extraction))

10. Precision

Repeatability: The difference between two results of repeated determinations by the same operator shall not exceed the following values.

11. Report

Take the arithmetic mean of two results of repeated determinations as the determination result of the sample.

12. 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 for Questions and Answers