NB/SH/T 0882-2014 Determination of extreme pressure properties of lubricating oils SRV testing machine method

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Card type: Test method

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

• Standard number: NB/SH/T 0882—2014
• Chinese full title: Determination of extreme pressure properties of lubricating oils SRV testing machine method
• English name: Standard test method for determining extreme pressure properties of lubricating oils using SRV test machine
• Replacement relationship: not provided in the available source (the foreword only states "adopted by modification using the redrafting method ASTM D 7421-11", and does not mention replacement of an old standard)
• Adoption relationship: modified adoption of ASTM D 7421-11 "Standard Test Method for Determination of Extreme Pressure Properties of Lubricating Oils Using a High-Frequency Linear Reciprocating (SRV) Testing Machine"
• Main technical differences from ASTM D 7421-11 (foreword):
  • Some referenced standards were modified to the corresponding national standards of our country
  • Some terms and definitions were changed to the corresponding terms and definitions of our country
  • For ease of use, the cleaning solvent was changed to petroleum ether (boiling range 90 ℃～120 ℃)
  • To facilitate determination of the maximum test load at which seizure does not occur (pass/OK load value), informative Annex A "Example of Determining Seizure from the Sample Friction Coefficient Curve" was added
• Publication/implementation: published on 2014-06-29, implemented on 2014-11-01
• Issuing body: National Energy Administration
• Secretariat: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC1)
• Drafting organizations: Sinopec Research Institute of Petroleum Processing, Lanzhou Lubricating Oil Research and Development Center of PetroChina Lubricant Company
• Main drafters: Lüqiu Qiming, Song Haiqing, Yang He, Lei Ailian, Wang Aixiang, Xue Ying
• Drafting rules: drafted in accordance with GB/T 1.1—2009

2. Scope of application and non-applicability

• Scope of application: specifies a test method for determining the extreme pressure properties of lubricating oils using a SRV testing machine under high-frequency linear reciprocating motion conditions; applicable to hydraulic oils, gear oils, engine oils, etc.
• Non-applicability: no explicit non-applicability clause is provided in the available source.
• Method application (Chapter 5): can rapidly determine the extreme pressure properties of lubricating oils under selected temperature conditions, and is especially suitable for occasions of high-frequency linear reciprocating motion or start-stop motion under high Hertzian point contact conditions; it is widely used to investigate the service performance of various lubricating oils for friction pairs such as constant velocity joints of front-wheel drive automobiles, gear hydraulic circulation systems, rear axles, gears, and engine components. Users of the standard should determine whether the results are relevant to field performance or other applications.

3. Method principle

This method uses a SRV or similar testing machine to cause linear reciprocating motion between a test ball and a test disk in the presence of a lubricant. The test load is increased in increments of 100 N until seizure occurs. The load value at which seizure is about to occur is determined and reported, and is called the OK load value. This load value can also be converted into Hertzian contact stress. Note: The motion frequency, stroke length, temperature, and the materials of the ball and disk can be changed to simulate actual conditions. The test ball usually produces a point-contact geometry. To obtain line or surface contact, test pieces of different shapes may be used to replace the test ball.

4. Reagents and materials (purity / preparation)

• Cleaning solvent: petroleum ether (boiling range 90 ℃～120 ℃), analytical reagent grade.
• Warning: flammable, harmful to health.
• Test oil amount: place 0.3 mL of test oil at the center of a clean test disk (see 9.6).
• Other reagents: not provided in the available source.

5. Apparatus and equipment

• Testing machine: SRV testing machine (schematic diagrams see Figure 1 to Figure 3); divided into I type, II type, III type, and IV type (the original text 8.1 is "SRV I type and II type", 8.2 is "SRV III type and IV type", source-text extraction unclear in the source text and requires confirmation against the source standard).
• Test ball: AISI 52100 steel or similar material, HRc 60±2, Ra 0.025 μm±0.005 μm, diameter 10 mm.
• Test disk: material is AISI 52100 steel produced by vacuum arc remelting or similar material; using ASTM A 295/A 295M or ASTM E 45 D method, the inclusion rating is A class, the severity level is 0.5, or according to ISO 683-17 the total impurity content is K≤10, and spherical carbides are obtained by spheroidizing annealing, HRc 62±2. The surface of the test disk should be ground and free of abrasive material. Test disk diameter 24 mm, thickness 7.8 mm. Surface morphology parameters must satisfy: 0.5 μm < Ra < 0.650 μm, 0.035 μm < R? < 0.050 μm, 0.020 μm < Rpk < 0.035 μm, 0.050 μm < Rvk < 0.075 μm (source-text extraction unclear in the source text and requires confirmation against the source standard; symbols and numerical ranges are subject to the original text).
• Test chamber structure (Figure 3): 1— reciprocating motion drive rod; 2— test ball holder; 3— loading rod; 4— test ball; 5— test disk; 6— resistance thermometer; 7— resistance heater; 8— test disk holder; 9— piezoelectric device; 10— base.
• Others: chart recorder, heating controller, load charge amplifier, digital timer, torque wrench, ultrasonic cleaner, laboratory paper towels, solvent-resistant gloves, tweezers, etc.

6. Recommended operating conditions

• Frequency: 50 Hz
• Stroke: 2.00 mm (the precision data also include 1 mm stroke, see Section 10)
• Test temperature: recommended 50 ℃, 80 ℃, and 120 ℃ (see Table 1)
• Preload: 50 N
• Break-in: run at 50 N for 30 s
• Loading program: apply up to 100 N and keep running for 15 min (including the loading process); thereafter increase the load by 100 N every 2 min until 1200 N, or the load limit of the testing instrument is reached, or failure occurs
• Note: because break-in at 50 N consumes 30 s, load application should begin at the 30 second mark of each odd minute
• SRV III type and IV type: the maximum load should be set to 2000 N; frequency 50 Hz; test temperature such as 50 ℃, 80 ℃, or 120 ℃; stroke 2 mm; run at 50 N for 30 s, then increase to 100 N and run for 15 min, thereafter increase the load by 100 N every 2 min
• Preheating: preheat the testing machine and chart recorder (or computer) for 15 min

7. Sampling and specimen preparation

• Specimen amount: place 0.3 mL of test oil at the center of the test disk (9.6).
• Cleaning of test ball/disk (9.1): wearing solvent-resistant gloves, wipe the surfaces of the test ball and test disk with laboratory paper towels moistened with cleaning solvent, repeatedly wiping until there is no black residue on the paper towel; immerse the test ball and disk in a beaker containing cleaning solvent and oscillate in an ultrasonic cleaner for 10 min; dry with clean paper towels, ensuring that no streaks appear on the surfaces.
• Sampling representativeness, sample preservation, etc.: not provided in the available source.

8. Analytical procedure

8.1 SRV I type and II type testing machine preparation

• 8.1.1 Before starting the test, turn on the testing machine and chart recorder and preheat for 15 min.
• 8.1.2 According to the instrument manual, select the position that produces the peak value of the friction coefficient. Note: in most cases this can be done by adjusting the slide switch on electronic board No.291.35.20E (located behind the front panel of the electronic equipment) and the slide switch on the rear panel of the control equipment.
• 8.1.3 Turn the amplitude knob to "zero".
• 8.1.4 Set the stroke adjuster to the automatic position.
• 8.1.5 Set the frequency to 50 Hz.
• 8.1.6 According to the manual, set the required range and calibrate the chart recorder, and select the required recording speed.
• 8.1.7 Turn on the heating controller and preheat the test disk holder to the required temperature (recommended 50 ℃, 80 ℃, 120 ℃, see Table 1); after the temperature stabilizes, preload 50 N, turn on the recorder, press the toggle switch until the timer starts counting, then adjust the stroke knob to 2.00 mm.
• 8.1.8 Set the load charge amplifier to the value corresponding to a load of 400 N.
• 8.1.9 If the friction coefficient at each load is to be investigated, change the load charge amplifier to the value corresponding to each load according to the manual.
• 8.1.10 When the digital timer reaches 30 s, use the slow speed position to apply the load to 100 N, and keep running at this load for 15 min (this 15 min includes the loading process).
• 8.1.11 Use the method of loading at the fast speed and fine-tuning at the slow speed, increasing the load by 100 N for every 2 min, until the load reaches 1200 N, or reaches the load limit of the test instrument, or failure occurs. Failure refers to the friction coefficient increasing by 0.2 compared with the steady-state value during the operation of the testing machine and exceeding 20 s, or shutdown occurring (see Appendix A).
• 8.1.12 When the 1200 N load operation ends, or the maximum load of the testing machine is reached, or failure occurs, the heating controller should be turned off, the load reduced to the minimum value (generally -13 N or -14 N), and then the test ball and test disk should be removed and cleaned.

Preparation of 8.2 SRV III type and IV type testing machines

• 8.2.1 Before starting the test, turn on the testing machine and computer to preheat for 15 min, input each test parameter through the control software (frequency = 50 Hz, test temperature, stroke = 2 mm), the test will run automatically, and can display and save the test results (friction coefficient, normal load, all load conditions, linear wear length, and sample temperature).
• 8.2.2 Input the following test parameters into the dynamic test program, the maximum load should be set to 2000 N: frequency 50 Hz; test temperature such as 50 ℃, 80 ℃ or 120 ℃; stroke 2 mm; run at load 50 N for 30 s, then increase the load to 100 N, run for 15 min, and thereafter increase the load by 100 N every 2 min.

9 Test procedure (applicable to all models of SRV testing machines)

• 9.1 Clean the test ball and test disk (see Section 7).
• 9.2 Ensure that the testing machine is under no load (load gauge reading is -13 N or -14 N) and install the test ball fixture (upper specimen fixture).
• 9.3 Then install the test disk (on the base), and tighten the fastening screws until resistance is felt.
• 9.4 Use tweezers to place the clean test ball into the cleaned and dried test ball fixture, and tighten the fastening screws until resistance is felt.
• 9.5 First tighten the test ball and test disk fixtures until resistance is felt, then apply a load of 50 N, and then use a torque wrench to tighten to 2.5 N·m.
• 9.6 Drop 0.3 mL of test oil into the center of the clean test disk.
• 9.7 Turn on the heating controller or set the temperature value in the software, preheat the test disk fixture to the required temperature, recommended to use 50 ℃, 80 ℃ and 120 ℃.
• 9.8 I type and II type machines complete the test according to 8.1.10～8.1.12, III type and IV type machines complete the test according to 8.2.1～8.2.2.

9. Qualitative and quantitative determination and calculation formulas

• Determination quantity: the maximum test load at which seizure does not occur (pass/OK load value), unit N; it can also be converted into Hertzian contact stress.
• Seizure determination criteria (3.11 Note): a sharp increase in the friction coefficient beyond the steady state, the friction coefficient increasing by 0.2 compared with the steady-state value, and the duration exceeding 20 s, in severe cases it can lead to shutdown (this determination criterion applies to liquid lubricants).
• Test validity check (10.2 Note 1): after the test, it is necessary to check and confirm that the test ball has not rotated, which can be judged by checking whether there are scratches on the edge of the wear scar, especially prone to occur at higher loads; if this occurs, the test is judged invalid.
• Precision calculation formulas (11.1.2, 11.1.3):
  • Repeatability r: 80 ℃ test r = 0.33X; 120 ℃ test r = 0.25X (Formula 1, Formula 2)
  • Reproducibility R: 80 ℃ test R = 0.47X; 120 ℃ test R = 0.44X (Formula 3, Formula 4)
  • Where: X—— the average of two results, N.
• Hertzian contact area/stress definition (3.3, 3.4): calculated according to the Hertzian elastic deformation equation; the Hertzian contact stress can be calculated and reported as the maximum value at the contact center Pmax or the average value over the total contact area Paverage (source-text extraction unclear in the source text, requires confirmation against the source standard).
• Table 1 gives the initial average Hertzian contact stress (derived from the average test load at the start of the test and the initial test morphology), example values in parentheses: <3006 MPa, <3255 MPa, <3139 MPa, <2889 MPa, <3598 MPa, <2987 MPa, <3567 MPa, <3270 MPa, <3342 MPa, <3093 MPa, <3218 MPa (source-text extraction unclear in the source text, requires confirmation against the source standard).

10. Precision

• 11.1.1 The following precision is suitable for lubricating oils tested on a SRV testing machine using a 2 mm stroke, capable of passing 1900 N or less than this load (95% confidence level).
  • Note 1: 28 cooperative laboratories conducted an international interlaboratory comparison test in 2006, selecting three lubricating oils with an average load-carrying capacity of approximately 800 N～1800 N on a SRV testing machine (SRV calibration oil, HLP46 hydraulic oil, factory-filled petroleum-based SAE 5W-30 engine oil), tested under two temperature conditions.
  • Note 2: This test can also be carried out using a 1 mm stroke, the comparison test data in Table 1 confirms the correctness of the precision, the test uses the same oils as the 2 mm stroke test.
  • Note 3: The precision values (r, R) represent the median values of the various oil types used in the comparison test.
• 11.1.2 Repeatability r: The difference between two consecutive test results obtained by the same operator using the same equipment on the same test material according to normal and accurate test methods should not exceed the values specified in Formula (1) and Formula (2): 80 ℃ test r = 0.33X; 120 ℃ test r = 0.25X.
• 11.1.3 Reproducibility R: The difference between two single, independent test results obtained by different operators in different laboratories on the same test material according to normal and accurate test methods should not exceed the values specified in Formula (3) and Formula (4): 80 ℃ test R = 0.47X; 120 ℃ test R = 0.44X.
• 11.2 Bias: This test method has no bias, because the load-carrying capacity of lubricating oils is evaluated according to this test method.
• Table 1 Precision determination data (oil sample I, oil sample II, oil sample III; test temperature 80 ℃, 120 ℃; stroke 1 mm, 2 mm; number of results, degrees of freedom, maximum test load, initial average Hertzian contact stress, standard deviation, reproducibility R, repeatability r) — the specific values in Table 1 are subject to verification item by item due to much noise in source-text extraction (source-text extraction); Table 1 Note 1: The load values passed by the extreme pressure of the lubricating oils listed in the table do not include outliers (data collected on 2006 year 10 month 15 day from SRV I type, II type, III type and IV type testing machines, test conditions: ball diameter d=10 mm; stroke = 1 mm or 2 mm; increase load by 100 N every 2 min; frequency = 50 Hz); Note 2: Repeatability and reproducibility were calculated using ASTM software (ADJD6300 D2PP), the values in parentheses represent the initial average Hertzian contact stress (derived from the average test load at the start of the test and the initial test morphology).

11. Report

10.1 Report the following information:

• Temperature, ℃;
• Stroke, mm;
• Frequency, Hz;
• Test ball material;
• Test disk material;
• Lubricating oil sample name (internal code or name, trademark and performance indicators). 10.2 General recommendation, the maximum test load at which seizure does not occur (pass/OK load value) should be reported. If required, a friction coefficient curve graph should also be included.
• Note 1: After the test, it is necessary to check and confirm that the test ball has not rotated. This can be judged by checking whether there are scratches on the edge of the wear scar. This is especially prone to occur at higher loads. If this occurs, the test is judged invalid.
• Note 2: The change in the friction force signal depends on the type of lubricating oil or grease under the test conditions. Different manifestations of the friction force curve do not necessarily indicate that adhesion has occurred. In test method ASTM D 5706, some typical examples are given to guide users in determining the moment when seizure occurs. These charts (see Appendix A) were approved by the DIN 51834 working group and the ASTM D02.GO technical committee in 2003, and the working group considers these charts also applicable to lubricating oils.

12. Reference documents

• GB/T 18778.2 Geometrical product specifications (GPS) surface texture: profile method—surfaces having stratified functional properties—part 2: height characterization using the linearized material ratio curve (GB/T 18778.2-2003, ISO 13565-2:1996, IDT)
• ISO 683-17 Heat-treated steels, alloy steels and free-cutting steels—part 17: rolling ball (bead) and roller bearing steels
• ASTM A 295/A295M Specification for high-carbon anti-friction bearing steels
• ASTM D 5706 Determination of extreme pressure properties of lubricating grease (SRV tester method)
• ASTM E 45 Determination method for impurity content in steel
• DIN 51834 Reciprocating motion tribology test
• GB/T 1.1—2009 (drafting rules stated in the foreword)
• ASTM D 7421-11 (source document for adoption)

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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