SH/T 0335-1992 Determination of Chemical Stability of Lubricating Grease

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 title / supersession relationship

• Standard number: SH/T 0335-92 (confirmed in 2004)
• Chinese title: Determination of Chemical Stability of Lubricating Grease
• English title: not provided in the available source
• Supersession relationship: supersedes SY 2715—77 (88)
• First issued: 1960
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented 1992-05-20

2. Scope of application and non-applicability

• Scope of application: This standard applies to lubricating grease.
• Non-applicability: not provided in the available source.

3. Method principle

Place the lubricating grease sample in an oxygen bomb under specified oxygen pressure and temperature for oxidation, and observe and record the pressure at specified time intervals. After the oxidation time ends, determine the acid value or free alkali of the sample after oxidation, and compare it with that before oxidation; use its change value and pressure drop to express the chemical stability of the sample.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 3.1.1 Petroleum ether: 90~120°C, analytical reagent; or solvent naphtha for the rubber industry.
• 3.1.2 95% ethanol: chemically pure.

4.2 Materials

• Industrial filter paper.

5. Apparatus and equipment

• 4.1 Oxygen bomb (see Figure 1): made of stainless steel containing nickel 8%~11% and chromium 17%~20%, or stainless steel close to that grade. The oxygen bomb consists of two main parts: the bomb body 8 and the bomb cover 7. The cover is connected to the bomb head; the bomb head includes the mushroom-shaped piece 6, the three-way tube 5 with lower side tube 4 and upper side tube 9, and the valve 3 with needle valve 2 and handwheel 1. The oxygen bomb cover can move up and down along the axis of the mushroom-shaped piece and can rotate on the enlarged part where the mushroom-shaped piece fits tightly with the oxygen bomb body. When the cover is tightened, the enlarged part of the mushroom-shaped piece tightly closes the oxygen bomb body. To clean the parts of the bomb head, it may be disassembled, but not more than once per year.
• 4.2 Oxygen pressure gauge: grade 1.5, diameter inside the pressure gauge case 150–200mm, scale 0–1.6MPa. Use a stainless steel high-pressure tube (bent into a spiral) to connect the pressure gauge to the lower side tube of the bomb head. To connect the pressure gauge, the side tube has an ordinary nut with a lead gasket. The side tube and the oxygen bomb are connected by a cone and nut. Only when the pressure gauge needs repair should it be removed from the oxygen bomb.
• 4.3 Carbon steel base frame: used to place the oxygen bomb when tightening the oxygen bomb and filling it with oxygen. This base frame should be tightened on a stable table.
• 4.4 Gasket: aluminum.
• 4.5 Wrench: for tightening the oxygen bomb; its size depends on the size of the protruding part of the oxygen bomb cover.
• 4.6 Oxygen cylinder: oxygen pressure not less than 1.0MPa.
• 4.7 Oxygen cylinder pressure reducing device: working pressure 0.1~1.5MPa.
• 4.8 High-pressure copper tube: used to connect the pressure reducing device and the oxygen bomb. Use a nut to connect the tube to the pressure reducing valve, and use a nut and cone to connect the tube to the oxygen bomb.
• 4.9 Water bath: with a temperature regulator to regulate the oxidation temperature of the lubricating grease.
• 4.10 Glass holder: used to place the cup containing the sample. The following parts are used when installing the holder:
  • 4.10.1 Glass rods: three "rods" with one thick end (shape as above), glass rod diameter 6mm±1mm, length 180mm±2mm, thick end diameter 8mm±1mm.
  • 4.10.2 Short glass tubes: 18 pieces, inner diameter 8mm±0.2mm, length 20mm±1mm, wall thickness 1mm±0.1mm.
  • 4.10.3 Six flat round glass plates: diameter 55mm±1mm, thickness 3mm±0.1mm, each glass plate has three holes, diameter 7.5mm±0.2mm, the holes are 3mm±0.1mm from the edge of the glass, and the distances between the three holes are equal (the distance between the centers of each hole is 35mm±1mm).
• 4.11 Glass cup: for holding the sample, diameter 30mm±2mm, height 12mm±1mm, wall thickness 1mm±0.1mm.
• 4.12 Glass mercury thermometer: 0~150°C, scale division 1°C.
• 4.13 Weighing bottle: diameter 35~50mm.
• 4.14 Metal cylindrical container: height about 450mm, diameter 850mm, used to check the sealing condition of the oxygen bomb and to cool the oxygen bomb after oxidation.

6. Recommended operating conditions

• Oxygen filling of the oxygen bomb: slowly (within about 3min) fill the oxygen bomb with oxygen to a pressure of about 0.2MPa, then similarly slowly release the oxygen to the atmosphere so that the remaining pressure in the oxygen bomb is about 0.05MPa; repeat the operation twice, then introduce oxygen into the oxygen bomb again until its pressure reaches the amount specified in the product standard for the sample.
• Water temperature for leak-tightness test: 20°C±3°C.
• Water bath temperature: specified temperature (accurate to ±2°C).
• Pressure recording interval: record the pressure once every 2h.
• Cooling water temperature after oxidation: 20°C±3°C, the oxygen bomb is immersed in water for at least 15min.
• The length of oxidation time and the index of pressure drop in the oxygen bomb: both are specified in the product standard for the sample.

7. Sampling and sample preparation

• 5.3 Determine the free alkali or acid value of the sample, then take about 4g from the sample, weigh to the nearest 0.1g, place it in one glass cup, similarly fill the remaining four glass cups, and place them separately on each layer of round glass of the holder, but leave the topmost round glass empty without placing a glass cup.
• 5.1 Before the test, wash the inside of the oxygen bomb body with petroleum ether or solvent naphtha, and dry it with a stream of air. Carefully wipe the bomb cover with all its parts using filter paper. Wash the glass "rods", flat round glass plates, short glass tubes, and glass cups in order with petroleum ether and 95% ethanol, and dry them in a thermostat or in a stream of air.

8. Analytical procedure

• 5.2 When installing the glass holder, place one short glass tube on each glass "rod", then place one flat round glass plate on these three glass tubes, then place one short glass tube on each glass "rod", and continue in this way until all six flat round glass plates are placed.
• 5.4 Carefully move the glass holder with the sample into the oxygen bomb previously placed on the base frame, add a gasket at the sealing point, then cover the oxygen bomb with the cover and tighten it with a wrench. Connect the prepared oxygen bomb to the pressure reducing valve of the oxygen cylinder using a high-pressure copper tube and an appropriate nut.
• 5.5 After the oxygen cylinder is connected to the oxygen bomb, blow oxygen into the oxygen bomb to expel the air therein. For this purpose, slowly (within about 3min) fill the oxygen bomb with oxygen to a pressure of about 0.2MPa, then similarly slowly release the oxygen to the atmosphere so that the remaining pressure in the oxygen bomb is about 0.05MPa. Repeat this operation twice, then introduce oxygen into the oxygen bomb again until its pressure reaches the amount specified in the product standard for the sample.
• 5.6 Remove the oxygen bomb filled with oxygen from the base frame, and carefully immerse it in a container with water at a temperature of 20°C±3°C to test its leak-tightness. If bubbles appear in the water, move the oxygen bomb back onto the base frame, tighten the leaking parts, and then repeat the leak-tightness test by the above method until it is completely sealed and leak-free. According to room temperature and the specified test conditions (pressure and temperature), determine the initial pressure in the bomb P₀ (MPa) by the following formula.
  • Formula: P₀ = P / [1 + (t_s − t) / (273 + t)] (the original formula is typeset as a fraction, source-text extraction appears as "P. 1+273 ( )", the specific form requires confirmation against the source standard (source-text extraction))
  • Where: P— the specified pressure of oxygen in the bomb at the specified test temperature, MPa; t_s— the specified temperature during the test, °C; t— room temperature, °C.
  • The initial pressure of oxygen in the oxygen bomb should be calculated to the nearest 0.01MPa.
  • According to the calculation result, release the excess oxygen in the oxygen bomb.
• 5.7 While preparing the oxygen bomb, heat the water bath to the specified temperature (accurate to ±2°C).
• 5.8 Keep the oxygen bomb filled with oxygen and containing the sample in a vertical position, carefully move it into the water bath heated to the specified temperature, and place it in the nest hole of the holder. A simplified diagram of the apparatus is shown in Figure 2. The time when the oxygen bomb is placed in the constant-temperature water bath is taken as the start of oxidation. At this time, record the time and the initial pressure in the oxygen bomb. Then, during the test, record the pressure once every 2h.
• 5.9 After some time, because the sample in the oxygen bomb becomes hot, the pressure in the oxygen bomb begins to rise; after reaching a certain limit, depending on the properties of each sample, it will remain unchanged for a considerable time. After another period of time, the pressure in the oxygen bomb begins to decrease; this period is considered the induction period of the sample. The length of oxidation time and the index of pressure drop in the oxygen bomb are both specified in the product standard for the sample.
• 5.10 After the oxidation time ends, carefully move the oxygen bomb into a container with water at a temperature of 20°C±3°C, and immerse the bomb completely in the water. At this time, because the temperature decreases, the pressure in the oxygen bomb begins to decrease. Keep the oxygen bomb immersed in water for at least 15min to cool it and check its leak-tightness. If bubbles are found in the water, the test is considered invalid and must be repeated.
• 5.11 After the oxygen bomb is cooled, move it onto the base frame and immediately release the residual oxygen in the oxygen bomb, then wipe all parts outside the oxygen bomb to remove moisture and dirt, then unscrew the cover and remove the cover from the bomb body. Use filter paper to absorb moisture on the protruding part of the top of the oxygen bomb, and carefully take the glass holder containing the sample out of the oxygen bomb.
• 5.12 Carefully take the oxidized sample out of each glass cup, place it in a weighing bottle, and stir carefully. Determine the acid value or free alkali of the sample after oxidation, and compare it with that before oxidation; use its change value and pressure drop to indicate the chemical stability of the sample.

9. Qualitative and quantitative determination and calculation formulas

• The chemical stability of the sample is expressed by the change value of acid value or free alkali before and after oxidation and the pressure drop.
• Formula for calculating the initial pressure in the bomb: P₀ = P / [1 + (t_s − t) / (273 + t)] (the original formula source-text extraction appears as "P. 1+273 ( )", the specific form requires confirmation against the source standard (source-text extraction))
  • P— the specified pressure of oxygen in the bomb at the specified test temperature, MPa
  • t_s— the specified temperature during the test, °C
  • t— room temperature, °C
  • Calculation accurate to 0.01MPa
• Induction period: the period during which the pressure in the oxygen bomb begins to decrease is considered the induction period of the sample.
• Length of oxidation time and pressure drop index: specified in the product standard for the sample.

10. Precision

• 6 Report: take the arithmetic mean of two results from duplicate determinations as the determination result.
• Other precision indexes: not provided in the available source.

11. Report

• Take the arithmetic mean of two results from duplicate determinations as the determination result.

12. Normative references

• Not provided in the available source (the main text does not list a normative reference document list).

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 Q&A