SH/T 0202-1992 Extreme-Pressure Properties of Lubricating Greases (Four-Ball Method)

AI-translated method card — human verification pending. This is not an official translation of the standard. Check the original controlled standard before use.

Source limitations: The available method card does not reproduce the full load and corrected-load tables or the figures. The load-wear index division formula was checked against the stored scan and corrected; independent review remains pending. The percentage wording for maximum non-seizure load is ambiguous and must not be used as a confirmed operating threshold. The Hertz formulae, timing unit and adoption-reference number were visually compared, but their independent review and the original source-card warnings remain pending. This card is not the complete standard and does not establish current validity, technical equivalence or product suitability.

1. Method number / title / English title / replacement

• Standard number: SH/T 0202-92
• Translated Chinese title: Determination of Extreme-Pressure Properties of Lubricating Greases (Four-Ball Method)
• English title: Not found in the source.
• Replacement: Replaces ZB E36 019-89.
• Referenced adoption: ASTM D2596-82 (the source-card OCR reads "D25% -82"; verification pending). This reference does not establish technical equivalence.
• Approval / implementation: Approved by China Petrochemical Corporation on 1992-05-20; implemented on 1992-05-20.

2. Scope and exclusions

• Scope: This standard specifies the determination of extreme-pressure properties of lubricating greases on an extreme-pressure four-ball tester. It evaluates grease load-carrying capacity using the load-wear index ZMZ and weld load P_D.
• Exclusions: Greases with silicone, halogenated silicone, or mixtures of silicone and mineral oil as the base oil are excluded.

3. Principle

Under a specified load, the upper steel ball rotates against the three stationary lower balls at 1770 r/min ±60 r/min with the grease at 27°C ±8°C. Increase the load in steps for a series of 10s tests. After each test, measure the wear-scar diameter on any one or all three balls in the cup, continuing until welding occurs.

4. Reagents and materials (purity / preparation)

• 6.1 Solvent oil: Meets the requirements for grade 190 in GB 1922.
• 6.2 Petroleum ether: 60–90°C, analytical grade; alternatively, solvent oil meeting the requirements for grade 90 in GB 1922.
• 6.3 Steel balls: Test balls specifically for the four-ball tester, made of high-quality chromium-alloy bearing steel GCr15, diameter 12.7 mm, Rockwell hardness HRC 64–66.
• Note: Do not clean with carbon tetrachloride or other solvents with load-carrying properties, because they affect the test results.

5. Apparatus

• 5.1 Extreme-pressure four-ball tester: Spindle speed at least 1800 r/min and load capacity at least 4901 N (500 kgf). After the collet holding the ball is installed in the spindle taper, radial runout of the ball must not exceed 0.02 mm. See Figure 2 for the tester schematic.
  • Note: Distinguishing an extreme-pressure four-ball tester from a wear four-ball tester is important. Preferably, do not perform both extreme-pressure and wear tests on the same tester, to avoid affecting wear-test sensitivity.
• 5.2 Microscope: Equipped with a calibrated micrometer graduated in 0.01 mm.
• 5.3 Timer or stopwatch: Accurate to 0.1s (the source-card OCR reads "0.18"; verification pending).
• 5.4 Friction recorder.

6. Operating conditions stated in the source

• Spindle speed: 1770 r/min ±60 r/min (7.1: Start the motor, adjust the spindle to 1770 r/min ±60 r/min and run unloaded for 2–3 min).
• Grease temperature: 27°C ±8°C.
• Test duration: Run for 10s ±0.2s.
• Load levels: Apply successive load levels according to Table 1.

7. Sampling and specimen preparation

• 8.1 Fill the ball cup with test grease at 27°C ±8°C, avoiding air bubbles. Place three clean balls in the cup, carefully press the retaining ring onto them, tighten the retaining nut and scrape off excess grease squeezed out by the nut.
• 7.2 Clean the balls, cup, collet and other parts contacting the specimen with solvent oil, then wash twice with petroleum ether and blow dry. Cleaned balls must be bright and free of rust spots.

8. Procedure

• 8.2 Insert a clean ball into the collet and install the collet on the tester spindle.
  • Note: The collet is continually subject to wear and seizure. Inspect it carefully before each test; replace it promptly if the test ball does not fit tightly or the collet shows seizure marks.
• 8.3 Place the assembled cup on the tester seat, bring the upper ball into contact with the three balls in the cup and slowly apply the specified load.
• 8.4 Start the motor and run for 10s ±0.2s.
• 8.5 After each test, measure the wear-scar diameter as follows.
  • 8.5.1 Method A: Remove the nut and balls, wipe off the grease, place a ball in a suitable holder and use the microscope to measure the wear scar on any one of the three balls, perpendicular and parallel to the direction of rotation, to 0.01 mm.
  • 8.5.2 Method B: Leave the balls in the cup, wipe excess grease from the balls and cup with a soft cloth or paper, then measure with the microscope using Method A and report the wear-scar diameter (mm).
  • Note: Before using Method A or B, visually inspect the balls for obvious differences in wear-scar diameter. If differences are obvious, measure all three balls and adjust the tester if necessary.
• 8.6 Record the mean wear-scar diameter from each test in Table 1.
• 8.7 Determination of maximum non-seizure load P_B: The source-card wording says the wear-scar diameter must be "not greater than 5% of" the corresponding diameter on the compensation line (the compensation diameter). This wording is ambiguous relative to the comparison that follows and must be verified, not applied literally as an operational threshold. If the measured scar exceeds the corresponding compensation diameter by more than 5%, test at the next lower load (Table 2) and compare again, continuing until the maximum non-seizure load is established. To simplify the procedure, the method provides the P–D_compensation(1+5%) table (Table 2) for judging P_B. D_compensation(1+5%) in Table 2 denotes the comparison diameter corresponding to load P. For example, a grease gives a 0.47 mm scar at 785 N (80 kgf), while Table 2 gives D_compensation(1+5%) = 0.44 mm; P_B is therefore below 785 N (80 kgf). Test at the next lower load. If the measured diameter is below D_compensation(1+5%), that load is the grease's P_B point.
  • Note: When a friction-measuring instrument is used, maximum non-seizure load can be recognized from gradual lateral movement of the recording pen.
• 8.8 Determination of weld load P_D: Perform a series of tests at successively higher loads from Table 1. Record the measured wear-scar diameters and replace the balls and grease each time until welding occurs. Repeat a test at the load where welding occurred. If welding does not recur, test at the next higher load until welding is verified.
  • Note: Switch off the motor immediately when welding occurs, otherwise the machine may be damaged. Observe the test to avoid excessive wear or seizure of the balls and collet. Welding may be indicated by one or all of these signs: sudden lateral movement of the friction-recorder pen, increased motor noise, smoke from the ball cup, or a sudden drop of the loading lever arm.

9. Definitions and calculation formulae

• 3.1 Load-wear index ZMZ: An index of the grease's extreme-pressure resistance under load. Loads are applied to the three stationary balls in increments of 0.1 logarithmic units. Use the ten test results preceding the weld load to calculate ZMZ by Equation (4) in Clause 10.2.
• 3.2 Weld load P_D: The minimum load at which the rotating ball welds to the three stationary balls under the test conditions, indicating that the grease's extreme-pressure capacity has been exceeded.
  • Note: Some greases do not produce actual welding; instead, the three stationary balls undergo severe scuffing. In that case, use the load producing a maximum wear-scar diameter of 4 mm as the weld load.
• 3.3 Corrected load: For each test, the applied load multiplied by the ratio of the Hertz diameter at that load to the measured wear-scar diameter.
• 3.4 Hertz diameter: The indentation diameter resulting from deformation of the balls under static load, calculated by Equation (1) or (2):
  • D_h = 4.08 × 10^(-2) (P_N)^(1/3) ………………(1)
  • D_h = 8.73 × 10^(-2) (P)^(1/3) ………………(2)
  • Where D_h is the Hertz diameter of the contact area, mm; P_N is the static load, N; and P is the static load, kgf.
  • Note: The source-card OCR of the coefficients and exponents is noisy; verification remains pending.
• 3.5 Compensation wear-scar diameter: The mean scar diameter produced by the upper rotating ball on the lower stationary balls in the presence of grease under loads that do not cause seizure or welding.
• 3.6 Hertz line: A straight line plotted on logarithmic axes with Hertz diameter (mm) against applied load N (kgf); see Figure 1.
• 3.7 Compensation line: A straight line plotted on logarithmic axes with wear-scar diameter (mm) against applied load N (kgf); see Figure 1.
• 3.8 Maximum non-seizure load: The maximum load without seizure under the test conditions. The source-card wording states that the mean scar diameter does not exceed "5% of" the corresponding compensation-line value; this threshold wording remains ambiguous and requires verification against the comparison procedure.
• 3.9 Initial-seizure region: The load region causing instantaneous rupture of the grease film. Film rupture is indicated by a sudden increase in scar diameter and a sudden deflection of the friction-measuring pointer; see Figure 1.
• 10.1 Corrected load P_S [N (kgf)]: Calculate by Equation (3) and record in Table 1 the corrected load for each applied load between maximum non-seizure load and weld load:
  • P_S = L × D_h / X ………………(3)
  • Where L is the applied load, kgf; for a lever-type four-ball tester, L is the total applied weight (weights and counterweights) multiplied by the lever-arm ratio; D_h is the Hertz diameter, mm; and X is the mean wear-scar diameter, mm.
• 10.2 Load-wear index ZMZ [N (kgf)]: Calculate by Equation (4) and record in Table 1:
  • ZMZ = A / 10 ………………(4)
  • Where A is the sum of the corrected loads for the 10 applied loads preceding the weld load.
  • Note: First, if the grease follows the compensation line, A is the sum of the corrected loads on the compensation line preceding welding (Table 3) and those outside the compensation line (calculated by Clause 10.1), covering 10 load levels in total.
  • Second, if the grease results do not follow the compensation line, Table 3 cannot be used. Perform tests at the 10 load levels preceding welding, then calculate the load-wear index by Clause 10.2.
• 10.3 Weld load P_D [N (kgf)]: Verify the weld load by Clause 8.8.
• Explanation of Table 3: For convenience, Table 3 gives corrected loads for any segment of the compensation line, found in Table 3 at the intersection of the maximum non-seizure load and weld load columns. For example, the maximum non-seizure load of a grease is 490 N (50 kgf), followed by tests at 618, 784, 981, 1236 and 1569 N (63, 80, 100, 126 and 160 kgf), with welding at 1961 N (200 kgf). The value from Table 3 at the intersection of 490 and 1961 N (50 and 200 kgf) is 1457.3 N (148.6 kgf). This compensation-line corrected load is the sum of corrected loads calculated using compensation diameters for 490, 392, 314, 235 and 196 N (50, 40, 32, 24 and 20 kgf). Calculate the corrected loads outside the compensation line by Clause 10.1.

10. Precision

Judge the reliability of results by the following requirements (95% confidence level).

• 9.1 Repeatability: For duplicate tests on the same specimen by the same operator with the same equipment under the specified conditions, the difference must not exceed:
  • Load-wear index ZMZ: 127 N (13 kgf).
  • Weld load P_D: One load increment.
• 9.2 Reproducibility: For tests on the same specimen by different operators in different laboratories, the difference between the two laboratories' results must not exceed:
  • Load-wear index ZMZ: 157 N (16 kgf).
  • Weld load P_D: One load increment.

11. Report

• Record the mean wear-scar diameter measured after each test in Table 1.
• 10.1 Calculate and record corrected load P_S [N (kgf)] by Equation (3) in Table 1.
• 10.2 Calculate load-wear index ZMZ [N (kgf)] by Equation (4) and record in Table 1.
• 10.3 Verify weld load P_D [N (kgf)] by Clause 8.8.
• Table 1, four-ball test record, includes: test number, conditions, test oil name, test materials, test oil formulation, date, load level, load N (kg), wear-scar diameter, compensation wear-scar diameter, coefficient, corrected load and remarks; record P_B, P_D and ZMZ as the results and identify the operator.
• 8.5.2 Method B requires microscope measurement and reporting of the wear-scar diameter (mm).

12. Referenced documents

• GB 1922 Solvent oil.

13. Source and verification status

• Pending OCR checks in the source card: ASTM D2596-82 was read as "D25% -82"; coefficients and exponents in Hertz-diameter Equations (1) and (2); timer accuracy "0.18", suspected to mean "0.1s"; extensive OCR noise in Tables 2 and 3 prevented reliable reconstruction. Some load levels and coefficients in Table 1 are readable, but the complete table remains unverified.

14. Quick questions and answers