GB/T 11144-2007 Standard test method for measurement of extreme-pressure properties of lubricating fluids — Timken method

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This standard specifies a method for determining the load-carrying capacity of lubricating fluids using the Timken extreme-pressure tester, and is applicable to the evaluation of the extreme-pressure properties of lubricating fluids.

Evidence note: the content of this page is compiled from the original text of this standard held in the Origin Standard library (where marked [to be verified] the original is [source unclear]); for individual values and for the current status, refer to the original pages of the standard and the product certificate. Verification note: [to be verified] and [source unclear] mark places where the original text of the standard still has to be checked and do not mean that verification has been completed. Do not use these values or steps directly as a basis for work.

Scope: This standard specifies a method for determining the load-carrying capacity of lubricating fluids using the Timken extreme-pressure tester, and is applicable to the evaluation of the extreme-pressure properties of lubricating fluids. NOTE (1.1): suitable for samples with a viscosity below 5 000 mm²/s at 40 °C; for samples of higher viscosity, refer to NOTE 2 in 9.1. 1.2 This standard uses SI units; the equipment used in this standard, however, is in imperial units, so imperial units have been retained where test equipment and test pieces are concerned. 1.3 This standard involves certain hazardous materials, operations and equipment, but it is not intended to address all safety problems associated with them; users should establish appropriate safety and protection measures and determine the applicable management system before using this standard, see Annex C. Differences from GB/T 11144-1989 (foreword): the title changed from "Lubricating oils — Determination of extreme-pressure properties (Timken tester method)" to "Standard test method for measurement of extreme-pressure properties of lubricating fluids — Timken method"; this standard, at a test temperature of 37.8 °C ± 2.8 °C, is suitable for samples with a viscosity at 40 °C of not more than 5 000 mm²/s, whereas the 1989 edition was suitable for samples with a viscosity at 37.8 °C of not more than 5 400 mm²/s; for precision differences see clause 10. Not applicable: the material available provides no specific clause on non-applicability.

Principle: Before the test begins the sample is preheated to 37.8 °C ± 2.8 °C. During the test a steel test ring rotates in close contact with a steel test block. The rotational speed is 123.71 m/min ± 0.77 m/min (405.88 ft/min ± 2.54 ft/min), equivalent to a shaft speed of 800 r/min ± 5 r/min. 4.2 Two values are to be determined: the minimum mass (weight) at which rupture of the oil film between the rotating ring and the stationary block causes seizure or scoring, that is the scoring value; and the maximum mass (weight) at which the oil film between the rotating ring and the stationary block does not rupture and causes no seizure or scoring, that is the OK value. 5 Significance and use: this method is widely used to determine the extreme-pressure properties of lubricating fluids. Users should take account of the precision and bias of the method when setting specification values.

Apparatus: Timken tester: see Annex A and Figure 2. 6.2 Sample supply device: supplies the sample to the test pieces, see Annex A. 6.3 Loading device: capable of applying and removing the load weights at a uniform rate of 0.907 kg/s to 1.361 kg/s (2 lb/s to 3 lb/s). See Annex A. 6.4 Microscope: low magnification (50 to 60 times), of sufficient sharpness, fitted with a micrometer for measuring the wear scar width, with a measuring accuracy of ±0.05 mm (±0.002 in). 6.5 Timer: graduated in minutes and seconds. 6.6 Thermometer: mercury-in-glass thermometer, range 0 °C to 100 °C, graduation 0.1 °C. Annex A (normative) Timken extreme-pressure tester: A.1 The machine spindle drives the test ring against the stationary test block; the ring is mounted on the horizontal spindle and the block in the block holder. The spindle is supported on rolling bearings and driven by a 1.5 kW synchronous motor at 800 r/min ± 5 r/min. The machine must be rigidly mounted so that vibration does not affect the test result. A.1.1 Test block holder: a wedge holds the test block in the block holder, the holder has a recess that engages the sliding bearing of the spindle, and the bottom of the holder rests on the knife edge of the load lever. A.1.2 Ring spindle: a locking nut mounts the test ring on the spindle. The radial runout of the machine spindle shall not exceed 0.013 mm. With the ring mounted on the spindle, a radial runout greater than 0.025 mm will affect the test result and indicates that the spindle may be damaged and should be replaced. The radial runout of the ring and spindle should be checked periodically. A.1.3 Lever system: consists of the load lever and the friction lever. The load lever carries the block holder and is mounted on the knife edge of the friction lever. A.1.4 Load lever constant: the lever ratio of the load lever system is 10, meaning that a force of 4.45 N (1 lbf) applied to the weight pan produces 44.5 N (10 lbf) on the test block; the effective weight of the load lever and weight pan is marked on the lever arm. A.1.5 Sample supply device: an oil tank of about 3 785 mL and a piping system that allows the sample to flow by gravity to the test pieces; the tank is fitted with a heater to heat the sample. The sample flows into the oil pool and is returned to the tank by a pump. A 149 µm strainer and a magnet are fitted at the outlet of the oil pool to keep wear particles from entering the pump and causing wear. The flow rate of lubricant onto the ring and block is controlled by a three-way valve at the tank outlet. A.1.6 Loading device: required to add and remove load on the load lever automatically, continuously and uniformly. The loading rate is 0.907 kg/s to 1.361 kg/s (2 lb/s to 3 lb/s). For the loading rate measurement procedure see A.1.6.1 to A.1.6.5. A.1.7 Once the loading rate has been established it may, if necessary, be adjusted in two ways: by changing the rate of descent of the platform, or by adjusting the spring so that it stretches differently under load.

Reagents and reference materials: Acetone: conforming to GB/T 686. 7.2 Aviation washing gasoline: conforming to SH 0114. 7.3 Test ring: made of carburized steel, Rockwell hardness HRC 58 to 62 or Vickers hardness HV 653 to 756. The ring width is 13.06 mm ± 0.05 mm (0.514 in ± 0.002 in), the circumference 154.51 mm ± 0.23 mm (6.083 in ± 0.009 in), and the diameter 49.22 mm (the original is in the form 49.22 to +0.002 in; the value is [to be verified] [source unclear]); maximum radial eccentricity 0.013 mm (0.000 5 in). Surface roughness 0.51 µm to 0.76 µm (20 µin to 30 µin) C.L.A. (centre-line average). NOTE: the test ring is available from Falex Corporation, part number F-25061. 7.4 Test block: made of carburized steel, Rockwell hardness HRC 58 to 62 or Vickers hardness HV 653 to 756. The block surface is 12.32 mm ± 0.05 mm (0.485 in ± 0.002 in) wide and 19.05 mm ± 0.41 mm (0.750 in ± 0.016 in) long. Each block has four test surfaces, with a surface roughness of 0.51 µm to 0.76 µm (20 µin to 30 µin) C.L.A. (centre-line average). NOTE: the test block is available from Falex Corporation, part number F-25001 (the original reads FoZ5001, [to be verified] [source unclear]). 8.2 Cleaning requirement: never wipe the test pieces with a solvent that has load-carrying properties, such as carbon tetrachloride, since this would affect the test result.

Key conditions: Sample preheat temperature: 37.8 °C ± 2.8 °C (4.1, 9.1). Test temperature: 37.8 °C ± 2.8 °C (9.1). Rotational speed: 123.71 m/min ± 0.77 m/min (405.88 ft/min ± 2.54 ft/min), equivalent to a shaft speed of 800 r/min ± 5 r/min (4.1). Loading rate: 8.9 N/s to 13.3 N/s (2 lbf/s to 3 lbf/s) (9.3; A.1.6 states 0.907 kg/s to 1.361 kg/s, i.e. 2 lb/s to 3 lb/s). Running-in: 30 s (9.2). Running time per load stage: 10 min ± 15 s (9.3, 9.5). Suggested starting load: 133.4 N (30 lbf) (9.3). Load increment: 44.5 N (10 lbf) (9.6); below 133.4 N the decrement is 26.6 N (6 lbf) and the increment 13.3 N (3 lbf) (9.7). The lowest starting load must be a multiple of 26.6 N (6 lbf) (9.3). High-viscosity samples (above 5 000 mm²/s at 40 °C): these can usually not be tested at 37.8 °C ± 2.8 °C; limited test results show that testing after heating to 65.6 °C ± 2.8 °C has no effect on the OK value or the scoring value; the grease injector of SH/T 0203 may be used to determine high-viscosity samples at room temperature (NOTE 2 of 9.1). After each load stage, the sample in the tank should be cooled to 37.8 °C ± 2.8 °C and a new test ring fitted and the test block turned over when the spindle temperature is below 65.6 °C ± 2.8 °C (NOTE to 9.6).

Calculation and results: The contact pressure between ring and block may be calculated as required. Once the OK value has been determined, remove the test block, clean it with aviation washing gasoline and acetone and blow dry. Measure the wear scar width at the OK value with the micrometer on the microscope, to 0.05 mm (0.002 in). Calculate the contact pressure by equation (1) or (2): C₁ = [L(X+C)]/YZ or [20(X+G)]/Z (1) C₂ = 9.81[L(X′+0.454G)]/Y′Z′ (2) where: C₁ is the contact pressure in psi; C₂ is the contact pressure in MPa (the correspondence between the symbols in the original equation and the definitions appears to be misaligned [source unclear], [to be verified] [source unclear]); L is the load lever ratio, 10; X is the mass (weight) on the weight pan, lb; G is the load lever constant (marked on the lever arm of each machine); X′ is the mass (weight) on the weight pan, kg; Y is the wear scar length, 0.5 in; Y′ is the wear scar length, 12.7 mm; Z is the mean wear scar width, in.; Z′ is the mean wear scar width, mm. 10.2 For convenience, contact pressures expressed in psi are given in Table F.1. Qualitative judgement (NOTE to 3.7): when the lubricating film is present in quantity, a smooth wear scar is obtained on the block. When the film ruptures, scoring or surface damage of the block occurs, see Figure 1. The simplest and most easily recognized form of scoring is a relatively wide wear scar on the block with ploughing marks, and excessive metal build-up on the ring surface. The following case also occurs: the scar surface is relatively smooth but there is local damage, that is scratches extending beyond the wear scar, which is also regarded as scoring. In a further case, scratches occur within a smooth wear scar but do not extend beyond it, and this is not regarded as scoring.

Terms and definitions (clause 3): 3.1 Extreme-pressure additive: an additive that reacts with the metal surfaces in contact to form a high-melting-point inorganic film preventing welding, seizure (or pickup), scratching or scoring under high load. 3.2 Lubricant: a substance added between two relatively moving surfaces to reduce friction and wear. 3.3 Scoring: during the determination of the load-carrying capacity of a lubricant, the phenomenon in which, when the lubricant film ruptures, the block surface suffers wide, deep ploughing-type damage in the direction of sliding. 3.4 Wear: the phenomenon of continuous loss of material or residual deformation of the test piece surfaces during the determination of extreme-pressure properties. 3.5 Load-carrying capacity of a lubricant: generally the maximum load or pressure that the lubricant can bear under given test conditions without the contacting surfaces suffering scoring, seizure or surface welding between the metals. 3.6 OK value: during the determination of the load-carrying capacity of a lubricant, the maximum mass (weight) placed on the load lever weight pan without causing scoring or seizure. 3.7 Scoring value: during the determination of the load-carrying capacity of a lubricant, the minimum mass (weight) placed on the load lever weight pan at which scoring or seizure occurs. 3.8 Seizure or surface welding: local welding between the metal of the rubbing surfaces of the test pieces. When seizure occurs, streaks usually appear on the ring surface, friction and wear increase, or abnormal noise and vibration occur. Throughout this method the term seizure is to be understood as general seizure or surface welding.

Quality control: Precision: judge the reliability of the test results as specified below (95% confidence level). 12.1 Repeatability r: the difference between two repeat results obtained by the same operator using the same apparatus and following the specified correct method on the same sample shall not exceed: r = 30% × X (3) where X is the mean of the two test results, kg (lb). 12.2 Reproducibility R: the difference between two results obtained by different operators using different apparatus and following the specified correct method on the same sample shall not exceed: R = 74% × X where X is the mean of the two test results, kg (lb). 12.3 Typical repeatability and reproducibility: Table 1 gives typical repeatability and reproducibility limits for OK values. Table 1 Typical repeatability and reproducibility values | Mean OK value kg(lb) | Repeatability kg(lb) | Reproducibility kg(lb) | | --- | --- | --- | | 6.804(15) | 2.041(4.5) | 4.990(11) | | 13.608(30) | 4.082(9) | 9.979(22) | | 18.144(40) | 5.443(12) | 13.608(30) | | 22.680(50) | 6.804(15) | 16.783(37) | | 27.216(60) | 8.165(18) | 19.958(44) | | 31.752(70) | 9.525(21) | 23.587(52) | | 36.287(80) | 10.886(24) | 26.762(59) | Precision differences from GB/T 11144-1989 (foreword): in this standard, at OK loads not below 66.7 N (15 lbf), the repeatability is not more than 30% of the mean and the reproducibility not more than 74% of the mean; in the 1989 edition the repeatability was not more than 2 load stages and the reproducibility not more than 4 load stages. Annex E (informative) Examples of the use of precision: E.1 Repeatability example: the same operator determines the same sample twice within a short period; result 1 = 22.680 kg (50 lb), result 2 = 29.484 kg (65 lb). Mean X = 26.308 kg (58 lb); repeatability limit y = 30% × 26.308 = 7.711 kg (17 lb); difference between the two results z = 6.804 kg (15 lb). z is less than y, so the repeatability limit may be considered met. E.2 Reproducibility example: results for the same sample in two laboratories, laboratory 1 = 18.144 kg (40 lb), laboratory 2 = 34.019 kg (75 lb). Mean X = 26.308 kg (58 lb); reproducibility limit y = 74% × 26.308 = 19.504 kg (43 lb); difference between the two results z = 15.876 kg (35 lb). z is less than y, so the reproducibility limit may be considered met.

Normative references: GB/T 686 Chemical reagent — Acetone SH 0114 Aviation washing gasoline SH/T 0203 Standard test method for extreme-pressure properties of lubricating greases (Timken tester method) Basis of adoption: ASTM D2782-01, Standard Test Method for Measurement of Extreme-Pressure Properties of Lubricating Fluids (Timken Method) Annex G (informative) gives a comparison of the clause numbers of this standard with those of ASTM D2782-01 (Table G.1).

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