GB/T 8022-2019 Determination of Demulsibility Characteristics of Lubricating Oils

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Card type: Test method

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

• Standard number: GB/T 8022—2019
• Chinese name: Determination of Demulsibility Characteristics of Lubricating Oils
• English name: Determination of demulsibility characteristics of lubricating oils
• Replacement relationship: replaces GB/T 8022—1987 "Determination of Demulsibility Characteristics of Lubricating Oils"
• Method composition: divided into method A (applicable to samples not containing extreme pressure additives) and method B (applicable to samples containing extreme pressure additives)
• Issued/implemented: issued on 2019-10-18, implemented on 2020-05-01
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280)
• Drafting organization: Sinopec Lubricant Co., Ltd. Yanhua Branch
• Main drafters: Tian Deying, Chen Yonghong, Zhang Min
• Previous versions: GB/T 8022—1987

2. Scope of application and non-applicability

• This standard specifies the determination of the demulsibility characteristics of lubricating oil products.
• Applicable to the determination of the ability of oil and water to separate from each other in high- and medium-viscosity lubricating oils.
• Method A is applicable to samples not containing extreme pressure additives; method B is applicable to samples containing extreme pressure additives.
• Not applicable: no explicit non-applicability clause is provided in the available source.

3. Method principle

• Method A: Add 405 mL of oil sample and 45 mL of grade-two water to a special separatory funnel, stir at a certain rotation speed for 5 min at a temperature of 82 °C, allow to stand for 5 h, then measure and record the volume of water separated from the oil, the volume of emulsion, and the percentage of water in the oil.
• Method B: Add 360 mL of oil sample and 90 mL of grade-two water to a special separatory funnel, stir at a certain speed for 5 min at a temperature of 82 °C, allow to stand for 5 h, then measure and record the volume of water separated from the oil, the volume of emulsion, and the percentage of water in the oil.

4. Reagents and materials (purity / preparation)

• 5.1 Toluene: analytical reagent. (Warning: flammable, keep away from heat sources, sparks and open flames; vapor is harmful; toxic; keep container closed; ensure ventilation; avoid prolonged or repeated skin contact)
• 5.2 Cleaning solvent: trichloroethane or any solvent that can effectively remove oil traces from the stirrer, constant-temperature bath body, and other adhering liquids. (Warning: trichloroethane is harmful if inhaled or swallowed, irritating to the eyes, and at high concentrations can cause loss of consciousness or death. Note: some laboratories use heptane or mineral spirits as cleaning solvents; the effect of such cleaning solvents on the precision of this method has not been determined)
• 5.3 Acetone: chemical reagent. (Warning: vapor is extremely flammable and can cause flash fire)
• 5.4 Water: meets the requirements for grade-two water in GB/T 6682—2008.
• Preparation of water-saturated toluene solution (6.1, Appendix B): should be prepared at 60 °C±1 °C, with no suspended water present; see Appendix B for the preparation method.
  • B.5.2: Pour 700 mL~800 mL of toluene into a 1 L reagent bottle, add sufficient water (not less than 2 mL but not more than 25 mL) to ensure visible excess water in the bottle, tighten the cap, and shake thoroughly for 30 s.
  • B.5.3: Loosen the cap, place in the bath to equilibrate for 30 min; remove, tighten the cap, and shake carefully for 30 s.
  • B.5.4: Repeat B.5.3 three times.
  • B.5.5: It is permitted to place the water-saturated toluene solution in the bath to equilibrate for 48 h before use; if the equilibration is less than 48 h, it may be poured into a centrifuge tube and centrifuged at the same rotation speed, and the toluene carefully removed with a pipette, ensuring no contact with the free water at the bottom of the tube.
  • B.5.6: It is recommended to store the water-saturated toluene solution in a constant-temperature bath that has reached the centrifugation test temperature, ready for use at any time.

5. Apparatus and equipment

• 4.1 Stirrer: rotation speed satisfies 4 500 r/min±500 r/min and 2 500 r/min±250 r/min, detailed structure see Figure 1, Figure 2, Figure 3. Note: it is recommended to use an air motor to avoid injury from electrical sparks.
• 4.2 Separatory funnel: 500 mL, minimum graduation 5 mL; borosilicate heat-resistant glass tube, standard wall thickness, outer diameter approximately 54 mm, as shown in Figure 4.
• 4.3 Constant-temperature bath: should immerse at least two separatory funnels, ensuring the constant-temperature medium can immerse the separatory funnel to the 500 mL graduation line; maintained at 82 °C±1 °C; able to secure the separatory funnel; when oil and water are mixed, the vertical centerline of the separatory funnel should coincide with the vertical axis of the stirrer. Note: the use of silicone oil as the constant-temperature medium is not recommended.
• 4.4 Centrifuge:
  • a) capable of rotating two or more liquid-filled centrifuge tubes at a speed that produces 500~800 relative centrifugal force (rcf) at the tips of the centrifuge tubes.
  • b) the rotor, trunnions, trunnion cups and cushions should be tightly assembled to withstand the maximum centrifugal force; during centrifugation the trunnion cups and cushions should firmly hold the centrifuge tubes; the centrifuge should be covered by a metal casing of certain strength.
  • c) should have a heating and temperature control system to maintain the temperature at 60 °C±1 °C during operation, and can operate safely in a flammable gas environment.
  • d) centrifuges driven by electricity and heated, when used in hazardous areas, should meet all safety requirements for electrical equipment used in hazardous areas.
  • e) the rotation speed of the centrifuge rotor (n) is calculated according to formula (1): n = 1 335√(rcf/d), where n is in r/min, rcf is the relative centrifugal force, d is the rotation diameter (the distance between the tips of two opposing centrifuge tubes during rotation), in mm.
• 4.5 Centrifuge tube: conical, made of heat-resistant glass, dimensions as shown in Figure 5, graduations should be clear; calibration tolerances see Table 1.
• 4.6 Water bath: depth should submerge the centrifuge tube to the 100 mL graduation line, temperature can be maintained at 60 °C±1 °C; a solid metal block heating bath or other liquid heating bath may also be used.
• 4.7 Pipette: 50 mL.
• 4.8 Graduated cylinder: 50 mL and 100 mL.
• 4.9 Other auxiliary equipment can be found in Appendix A (sampler and centering device Figure A.1, siphon device Figure A.2, pressure device Figure A.3, solvent cleaning cylinder and hot air dryer Figure A.4).

Table 1 Calibration tolerances for centrifuge tubes

6. Recommended operating conditions

• Constant-temperature bath temperature: 82 °C±1 °C (same for method A and method B).
• Stirring speed: method A is 4 500 r/min±500 r/min; method B is 2 500 r/min±250 r/min.
• Stirring time: including start-up time, a total of 5 min; within 25 s~30 s, slowly increase the stirring speed to the specified rotation speed.
• Standing time: after stopping stirring, allow to stand for 300 min (i.e., 5 h).
• Centrifugation temperature: 60 °C±1 °C.
• Centrifugation relative centrifugal force: 500~800 rcf (centrifugation for water-in-oil determination); 700 rcf (centrifugation for emulsion determination).
• Centrifugation time: for water-in-oil determination, each time 10 min; for emulsion determination, 10 min~15 min.
• Preparation temperature of water-saturated toluene solution: 60 °C±1 °C.

7. Sampling and sample preparation

• 7.1.1 / 7.2.1: Take a representative sample for testing in accordance with GB/T 4756.
• Method A sample amount: 405 mL±5 mL (poured directly into the separatory funnel at room temperature).
• Method B sample amount: 360 mL±5 mL (poured directly into the separatory funnel at room temperature).
• Test water: method A uses 45 mL±0.5 mL (room-temperature volume) grade-two water; method B uses 90 mL±0.5 mL (room-temperature volume) grade-two water.
• Separatory funnel cleaning (6.2): first clean with cleaning solvent to remove all oil traces, then sequentially clean with acetone, tap water, and finally clean thoroughly with grade-two water.
• Stirrer cleaning (6.3): clean with cleaning solvent, blow dry before use (for cleaning equipment see Figure A.4).

8. Analysis Steps

8.1 Method A (applicable to samples containing no extreme pressure additives)

• 7.1.1 Sample according to GB/T 4756; raise the constant-temperature bath to 82 °C±1 °C and maintain throughout the test.
• 7.1.2 At room temperature, pour the 405 mL±5 mL test sample into a separatory funnel; place in the constant-temperature bath and hold until 82 °C; add 45 mL±0.5 mL (room-temperature volume) of grade-two water; immerse the stirrer into the sample so that the bottom end of the stirrer is at a distance of 25 mm from the lowest part of the centerline of the funnel; the vertical stirring shaft of the stirrer shall coincide with the central axis of the separatory funnel; within 25 s~30 s, slowly increase the stirring speed to 4 500 r/min±500 r/min, and stir for a total of 5 min including the startup time; after stirring ends, lift the stirrer and let it stand so that it drips into the separatory funnel for 5 min; remove the stirrer and clean it. Silicone-containing grease shall not be used to lubricate the separatory funnel stopcock; a polytetrafluoroethylene stopcock may be used, or a silicone-free lubricant may be used to lubricate the stopcock. Note: If the time to start the stirrer and reach the specified stirring speed is too short, erroneous results may occur.
• 7.1.3 After stopping stirring for 300 min, from a point on the centerline of the separatory funnel below the oil-water mixture liquid surface at 50 mm, use a 50 mL pipette to draw a 50 mL test sample into a centrifuge tube (for sampling auxiliary equipment see Figure A.1); use a pipette to add 50 mL toluene-saturated solution to the centrifuge tube, with the reading taken at the bottom of the 50 mL meniscus; stopper the centrifuge tube, shake thoroughly; loosen the centrifuge tube stopper, place the centrifuge tube into a 60 °C±1 °C bath and hold at constant temperature for 10 min.
• 7.1.4 Tightly stopper the centrifuge tube, carefully invert the centrifuge tube again, and shake the mixture uniformly.
• 7.1.5 To maintain balance during centrifugation, place two centrifuge tubes in trunnion cups in opposite positions, and adjacent or opposite centrifuge tubes and tube stoppers shall not touch; centrifuge at a speed sufficient to produce a relative centrifugal force of 500~800 at the tip of the centrifuge tube for 10 min; the temperature shall be maintained within 60 °C±1 °C throughout the centrifugation process.
• 7.1.6 After the centrifuge stops rotating (ensure that the centrifuge tube is in a vertical position when centrifugation stops), immediately read the total content of visible water and sediment at the bottom of the centrifuge tube. Reading rules: when the volume is between 0.1 mL–1 mL, read to the nearest 0.05 mL; when greater than 1 mL, read to the nearest 0.1 mL; when between 0.025 mL–0.1 mL, estimate to 0.025 mL (see Figure 5). If less than 0.025 mL or after estimation still less than 0.025 mL, record the volume as less than 0.025 mL; if there is no visible water and sediment, record the volume as 0.000 mL. Without agitating the liquid in the tube, repeat the centrifugation at the same rate for 10 min.
• 7.1.7 Repeat the operation of 7.1.6 until the volume reading of the total content of visible water and sediment in the same centrifuge tube remains unchanged after two adjacent centrifugations; record the result according to 8.2 as the "water percentage in oil".
• 7.1.8 Quickly remove the separatory funnel from the constant-temperature bath, transfer the separated water separated from the oil-water mixture into a 50 mL graduated cylinder; cool to room temperature and record the volume of separated water.
• 7.1.9 After draining the separated water, carefully withdraw liquid from the upper part of the separatory funnel through a siphon tube (see Figure A.2) so that its liquid level drops to the 100 mL mark; the end of the siphon tube shall always be no more than 20 mm from the liquid surface; discharge the remaining 100 mL liquid (including sample, water, and emulsion) together into a centrifuge tube; for high-viscosity oils or when a paste-like emulsion appears, pressure may be applied to the open end of the separatory funnel (see Figure A.3) to force the oil or emulsion to flow into the centrifuge tube.
• 7.1.10 Centrifuge this centrifuge tube at a speed of 700 rcf for 10 min~15 min; record the volume of visible water and emulsion separated.
• 7.1.11 Repeat steps 7.1.1~7.1.6, and determine each oil sample at least twice; if the two measurement results exceed the repeatability requirement specified in Method A, discard these two sets of data and retest.

8.2 Method B (applicable to samples containing extreme pressure additives)

• 7.2.1 Sample according to GB/T 4756; raise the constant-temperature bath to 82 °C±1 °C and maintain throughout the test.
• 7.2.2 At room temperature, pour the 360 mL±5 mL test sample into a separatory funnel; place in the constant-temperature bath and hold until 82 °C; add 90 mL±0.5 mL (room-temperature volume) of grade-two water; immerse the stirrer into the sample so that the bottom end of the stirrer is at a distance of 25 mm from the lowest part of the centerline of the funnel; the vertical stirring shaft of the stirrer shall coincide with the central axis of the separatory funnel; within 25 s~30 s, slowly increase the stirring speed to 2 500 r/min±250 r/min, and stir for a total of 5 min including the startup time; after stirring ends, lift the stirrer and let it stand so that it drips into the separatory funnel for 5 min; remove the stirrer and clean it. Note 1: If the time to start the stirrer and reach the specified stirring speed is too short, erroneous results may occur. Note 2: When determining high-viscosity or emulsified oil samples, the stirrer motor speed may decrease, and it is necessary to frequently check and adjust the speed during stirring.
• 7.2.3 After stopping stirring for 300 min, from a point on the centerline of the separatory funnel below the oil-water mixture liquid surface at 50 mm, use a 50 mL pipette to draw a 50 mL test sample into a centrifuge tube (for sampling auxiliary equipment see Figure A.1); use a pipette to add 50 mL toluene-saturated solution to the centrifuge tube, with the reading taken at the bottom of the 100 mL meniscus; stopper the centrifuge tube stopper, shake thoroughly; loosen the centrifuge tube stopper, place the centrifuge tube into a 60 °C±1 °C water bath for 10 min.
• 7.2.4 Tightly stopper the centrifuge tube stopper, carefully invert the centrifuge tube again, and shake the mixture uniformly.
• 7.2.5 To maintain balance during centrifugation, place two centrifuge tubes in trunnion cups in opposite positions, and adjacent or opposite centrifuge tubes and tube stoppers shall not touch; centrifuge at a speed sufficient to produce a relative centrifugal force of 500~800 at the tip of the centrifuge tube for 10 min; the temperature shall be maintained within 60 °C±1 °C throughout the centrifugation process.
• 7.2.6 After the centrifuge stops rotating (ensure that the centrifuge tube is in a vertical position when centrifugation stops), immediately read the total content of visible water and sediment at the bottom of the centrifuge tube. Reading rules: when the total volume is between 0.1 mL~1 mL, read to the nearest 0.05 mL; when greater than 1 mL, read to the nearest 0.1 mL; when below 0.1 mL, estimate to 0.025 mL (see Figure 5). If less than 0.025 mL or after estimation still less than 0.025 mL, record the volume as less than 0.025 mL; if there is no visible water and sediment, record the volume as 0.000 mL. Without agitating the liquid in the tube, repeat the centrifugation at the same rate for 10 min.
• 7.2.7 Repeat the operation of 7.2.6 until the volume reading of the total content of visible water and sediment in the same centrifuge tube remains unchanged after two adjacent centrifugations; record the result according to the method in 8.2 as the "water percentage in oil".
• 7.2.8 Quickly remove the separatory funnel from the constant-temperature bath, transfer the separated water separated from the oil-water mixture into a 100 mL graduated cylinder; cool to room temperature and record the volume of separated water.
• 7.2.9 After draining the separated water, carefully withdraw liquid from the upper part of the separatory funnel through a siphon tube (see Figure A.2) so that its liquid level drops to the 100 mL scale mark; the end of the siphon tube shall always be no more than 20 mm from the liquid surface; discharge the remaining 100 mL liquid (including sample, water, and emulsion) together into a centrifuge tube; for high-viscosity oils or when a paste-like emulsion appears, pressure may be applied to the open end of the separatory funnel (see Figure A.3) to force the oil or emulsion to flow into the centrifuge tube.
• 7.2.10 Centrifuge this centrifuge tube at a speed of 700 rcf for 10 min~15 min; record the volume of visible water and emulsion separated.
• 7.2.11 Repeat steps 7.2.1~7.2.6, and determine each sample at least twice; if the two measurement results exceed the repeatability requirement specified in Method B, discard these two sets of data and retest.

9. Qualitative and Quantitative and Calculation Formulas

• 8.1 Report the procedure used in the test as Method A or Method B.
• 8.2 Calculate the water percentage in oil X (%) according to formula (2) (see 7.1.7 or 7.2.7):
  • X = (V/50) × 100
  • Where: X—— water percentage in oil, %; V—— volume of visible water in the centrifuge tube, in milliliters (mL).
• 8.3 When the water percentage in oil is less than 0.1%, report "<0.1%" or "trace".
• 8.4 Report each determination result and the average of the determination results, including "water percentage in oil" (see 7.1.7 or 7.2.7), "total volume of separated water", and the "emulsion volume" separated by centrifugation (see 7.1.10 or 7.2.10). "Total volume of separated water" means the sum of the volume of separated water collected in the 50 mL (method A) or 100 mL (method B) graduated cylinder (see 7.1.8 or 7.2.8) and the volume of visible water separated by centrifugation (see 7.1.10 or 7.2.10).

10. Precision

• 9.1.1 Overview: Judge the reliability of test results according to the following provisions (confidence level of 95%). The precision of method A is shown in Table 2, and the precision of method B is shown in Table 3.
• 9.1.2 Repeatability: For two test results obtained consecutively by the same operator, in the same laboratory, using the same instrument, according to the same method, on the same test sample, the difference shall not exceed the value specified in Table 2 (method A) or Table 3 (method B).
• 9.1.3 Reproducibility: For two single, independent test results obtained by different operators, in different laboratories, using different instruments, according to the same method, on the same test sample, the difference shall not exceed the value specified in Table 2 (method A) or Table 3 (method B).

Table 2 Precision of method A

Table 3 Precision of method B

Note: * Estimated value obtained after examining the data. Note: In Table 3, there is a suspected misalignment in the correspondence between the text rows and columns of source-text extraction; the correspondence between the three rows of A/B/C and the values in each column requires confirmation against the source standard (source-text extraction).

• 9.2 Bias: Since the values of total volume of separated water and emulsion volume are defined only in this method, the test procedure of this method has no bias.

11. Report

• 8.1 Report whether the procedure used for the test is method A or method B.
• 8.2 Calculate according to formula (2) and report the water percentage in oil X (%).
• 8.3 When the water percentage in oil is less than 0.1%, report "<0.1%" or "trace".
• 8.4 Report each determination result and the average of the determination results, including "water percentage in oil", "total volume of separated water", and the "emulsion volume" separated by centrifugation. "Total volume of separated water" means the sum of the volume of separated water collected in the graduated cylinder and the volume of visible water separated by centrifugation.

12. Normative References

• GB/T 4756 Petroleum liquids — Manual sampling
• GB/T 6682—2008 Specifications and test methods for water for analytical laboratory use
• Note: For dated normative references, only the dated version applies; for undated normative references, the latest version (including all amendments) applies.

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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