Demulsibility Test Method for 68# Gear Oil

68# gear oil is a mixture composed of petroleum lubricating oil or synthetic lubricating oil, extreme pressure anti-wear agents, and oiliness agents. It features high viscosity-temperature performance, extreme pressure anti-wear properties, demulsibility, oxidation stability, thermal stability, anti-foaming ability, rust prevention, and corrosion resistance. At room temperature, it is a clear and transparent liquid ranging from pale yellow to amber, with a slight sulfurous or pungent odor and low toxicity. Its density at 15℃ is 0.842kg/L, viscosity at 40℃ is 68mm²/s, and viscosity index is 146. It is widely used in heavy-load industrial equipment.

Test Purpose

During service, gear oil is prone to contamination by moisture. Pumping and circulating turbulence may lead to the formation of water-in-oil emulsions, which reduce lubrication efficiency. This can result in increased gear wear, pitting corrosion, rust on the inner wall of gearboxes, and delayed response of hydraulic control systems, thereby affecting the safety and service life of the equipment. By simulating actual operating conditions, this test evaluates the performance of the product in practical use and provides a basis for oil selection, quality control, and maintenance cycle optimization.

Test Equipment

① SD8022 Lubricating Oil Demulsibility Tester

② Auxiliary tools such as separating funnel, pipette, graduated cylinder, toluene (analytical grade), and cleaning solvent

Test Procedures

① Inspect the equipment to ensure the instrument and all used vessels are clean and dry.

② Connect the power supply and heat the constant temperature bath to 82℃±1℃.

③ Extract the sample: pour 360ml±5ml of the sample into a separating funnel, place it in the constant temperature bath, and add 90ml±0.5ml of secondary water.

④ Immerse the stirrer into the sample, stir for 5 minutes, lift the stirrer to let it stand, and allow the liquid to drip from the separating funnel for 5 minutes.

⑤ After stopping stirring for 300 minutes, use a pipette to take 50ml of the sample from 50mm below the liquid surface of the mixture into a centrifuge tube. Add 50ml of toluene-saturated solution, seal and shake well, then place it in a 60℃±1℃ water bath for 10 minutes.

⑥ Start the centrifuge, centrifuge at 500-800 centrifugal force for 10 minutes, and read the total content of visible water and sediment at the bottom. Repeat the operation until the reading of total visible water and sediment in the same centrifuge tube remains unchanged.

⑦ Take out the separating funnel and record the volume of separated water.

⑧ Discharge the remaining 100ml of liquid into a centrifuge tube, centrifuge at 700rcf for 10-15 minutes, and record the volume of visible water and emulsion.

⑨ Repeat the measurement 1-3 times, record the data, and calculate the results.

Test Conclusion

In the demulsibility test of this 68# gear oil, the water content in the oil is 0.8%, the emulsion layer is 1.7ml, and the total separated water is 65ml, which complies with the GB/T 8022 standard.

Translation Notes

1. Term Standardization: Professional terms adopt industry-recognized English translations (e.g., "抗乳化" → "demulsibility", "极压抗磨剂" → "extreme pressure anti-wear agent", "粘度指数" → "viscosity index") to ensure accuracy in technical scenarios.

2. Unit Consistency: Physical quantity units (e.g., kg/L, mm²/s, ℃) follow international writing norms, and temperature tolerance expressions (e.g., 82℃±1℃) retain the original format for clarity.

3. Sentence Structure Optimization: Complex Chinese sentences are split into logical English clauses (e.g., the description of gear oil properties) to conform to English technical document writing habits, while maintaining the integrity of technical information.

4. Standard Reference: "GB/T 8022" retains the original standard number (GB/T denotes National Recommended Standard of China) for easy reference by international readers.

5. Precision of Test Data: All numerical values (e.g., sample volume, temperature, centrifugal force) are translated exactly to ensure the reproducibility of the test process.