GB/T 3498-2008 Determination of dropping point of lubricating grease over a wide temperature range

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Card type: Test method

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

• Standard number: GB/T 3498—2008
• Chinese title: Determination of dropping point of lubricating grease over a wide temperature range
• English title: Petroleum products—Determination of dropping point of lubricating greases (wide temperature range)
• Adoption relationship: modified adoption of ISO 6299:1998 (MOD)
• Replacement relationship: replaces GB/T 3498—1983
• Publication/implementation: published on 2008-06-23, implemented on 2008-12-01
• Proposed by/under the jurisdiction of: proposed by the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280); under the jurisdiction of China Petrochemical Corporation
• Drafting organization: Sinopec Research Institute of Petroleum Processing
• Main drafters: Jiang Liang, Liu Zhongqi

2. Scope of application and non-applicability

• This standard is applicable to the determination of the dropping point of lubricating grease over a wide temperature range.
• Note 1: The dropping point is useful for helping to identify the type of lubricating grease and for establishing a basis for quality control; however, because the dropping point determination is a static test, the test results are considered to be of limited significance for the service performance of lubricating grease.
• Note 2: Statistical tests show that, under normal circumstances, the dropping point data determined by this standard and by GB/T 4929 are consistent within the range of 260 ℃. When the results differ, this is also of no consequence, but the supplier and purchaser should reach agreement on the test method used.
• Non-applicable scope: not provided in the available source.

3. Method principle

Fill the lubricating grease into the grease cup, place it in a test tube, and place the test tube in an aluminum block furnace pre-set to a constant temperature. Place a thermometer in the test tube; the thermometer does not contact the lubricating grease sample, and the temperature inside the test tube is measured under conditions in which there is no contact with the sample. When the temperature inside the test tube rises to the point at which the first drop of the lubricating grease sample falls from the grease cup to the bottom of the test tube, record the temperature indicated by the thermometer as the observed dropping point, to the nearest 1 ℃. At the same time, record the temperature of the aluminum block furnace, to the nearest 1 ℃. Take one third of the difference between the aluminum block furnace temperature and the thermometer temperature in the test tube as the correction coefficient, and add it to the observed dropping point; this is the dropping point of the lubricating grease sample.

4. Reagents and materials (purity / preparation)

• Not provided in the available source (the main body of this standard does not list clauses for reagents and materials).

5. Apparatus and equipment

• 5.1 Dropping point apparatus: see Figure 1, consisting of the following components.
  • 5.1.1 Grease cup: chrome-plated brass cup, dimensions as shown in A of Figure 1.
  • 5.1.2 Test tube: thin-walled glass test tube with a rim, dimensions as shown in B of Figure 1.
  • 5.1.3 Grease cup holder: glass tube, as shown in C of Figure 1.
  • 5.1.4 Thermometer: meets the requirements for the GB-29 thermometer in GB/T 514, as shown in D of Figure 1.
• 5.2 Thermometer clamp: as shown in E-1 of Figure 1.
• 5.3 Bushing: as shown in E-2 and E-3 of Figure 1.
• 5.4 Bushing support ring: as shown in E-4 of Figure 1.
• 5.5 Thermometer depth gauge: as shown in E-5 of Figure 1.
• 5.6 Metal rod: as shown in E-6 of Figure 1.
• 5.7 Grease cup gauge: as shown in E-7 of Figure 1.
• 5.8 Aluminum block furnace: output power 700 W, design dimensions as shown in Figure 2. The aluminum block furnace shall be equipped with a complete cartridge heater, and the required temperature shall be obtained and maintained by controlling the heater.
• 5.9 Aluminum block furnace thermometer: as shown in F of Figure 1.
• Figure 1 component labels: A— grease cup; B— test tube; C— grease cup holder; D— thermometer; E-1— thermometer clamp; E-2— bushing; E-3— bushing; E-4— bushing support ring; E-5— thermometer depth gauge; E-6— metal rod; E-7— grease cup gauge; F— thermometer assembly; G— test tube assembly; E— knurling.
• Figure 2 aluminum block furnace labels: A— insulating material; B— yellow light; C— thermometer hole; D— thermistor probe; E—700 W heater.
• Dimension values for Figure 1 and Figure 2 (source-text extraction extracted, unit millimeters): the original figure notes contain 15.87, 58, 6.73, 7.11, 15.73, 12.7, 19, 11.10, 10.72, 88.9, R4.54, φ13.7, 40°, 39.5°, 10.71, 7.74, 7.71, 5.66, 76.2, inner diameter 4.7, inner diameter 4.5, 10.7, 2.8, 4.8, 9.4±0.13, 66, 5, 34, 190.5, 50.8, 13.8, 93.6, 22, 19, 22.2, φ6.3, φ12.7, etc.; the specific correspondences require confirmation against the source standard (source-text extraction).

6. Recommended operating conditions

• Furnace temperature settings (Table 1): 121 ℃±3 ℃, 232 ℃±3 ℃, 288 ℃±3 ℃, 316 ℃±3 ℃, 343 ℃±3 ℃.
• Table 1 maximum dropping point corresponding to aluminum block furnace temperature:
  • Aluminum block furnace temperature 121 ℃±3 ℃ → maximum dropping point temperature 116 ℃
  • Aluminum block furnace temperature 232 ℃±3 ℃ → maximum dropping point temperature 221 ℃
  • Aluminum block furnace temperature 288 ℃±3 ℃ → maximum dropping point temperature 277 ℃
  • Aluminum block furnace temperature 316 ℃±3 ℃ → maximum dropping point temperature 304 ℃
  • Aluminum block furnace temperature 343 ℃±3 ℃ → maximum dropping point temperature 330 ℃
• Selection principle (6.1.5): according to Table 1, select the lowest furnace temperature for the test under the condition that the measured dropping point of the sample is not higher than the maximum dropping point corresponding to that furnace temperature.
• The aluminum block furnace shall be capable of accommodating up to 6 identical or different lubricating grease samples for simultaneous dropping point determination; replicate determinations may be carried out simultaneously.
• Precision note: to obtain accurate values, if the dropping point of the lubricating grease is lower than 221 ℃, use a thick-walled heat-resistant glass test tube; if the dropping point of the lubricating grease is higher than 221 ℃, use a thin-walled test tube.

7. Sampling and sample preparation

• 6.2.1 Press the sample in from the large opening of the grease cup (5.1.1) until it is full. Use a scraper to remove excess grease so that the grease surface is flush with the cup opening. With the small opening of the grease cup facing downward and maintained in a vertical position, gently fit it onto the metal rod (5.6) until the metal rod extends about 25 mm beyond the large opening of the grease cup. Use the metal rod to simultaneously contact the upper and lower circumferences of the cup and press the grease in the cup; use the index finger to rotate the grease cup on the metal rod and move it downward in a spiral manner, so that the conical portion of the grease is adhered to the metal rod and removed. When the grease cup approaches the lower end of the metal rod, carefully slide the metal rod out of the grease cup, leaving a smooth grease film of uniform thickness inside the cup.
• Other sampling requirements: not provided in the available source.

8. Analytical procedure

• 6.1 Apparatus assembly
  • 6.1.1 Thoroughly clean the grease cup, grease cup holder, and test tube. The grease cup may be used only when it is clean and free of residue. If the plating inside the grease cup shows wear, stop using that grease cup.
    • 6.1.1.1 Before using a new grease cup, check the grease cup specifications with the grease cup gauge (5.7). Use the 2.78 mm gauge rod as the "go" gauge and the 2.83 mm gauge rod as the "no-go" gauge to check the size of the lower orifice of the grease cup. If the orifice size is not large enough, it must be reamed to the appropriate size. If the orifice is too large, the grease cup shall be discarded.
    • Note: if the grease cup is of suitable size, it is not necessary to re-measure its dimensions before every test.
  • 6.1.2 The test tube shall be clean and free of residue, and shall conform to the specifications and dimensions shown in B of Figure 1. Check the test tube for chips, cracks, or breakage, and replace it if necessary.
  • 6.1.3 The surface of the thermometer sensing bulb shall be clean and free of residue. Check whether the bushing (5.3) is clean and ensure that the thermometer clamp (5.2) completely and firmly secures the thermometer.
  • 6.1.4 The test tube used to support the grease cup shall be free of chips, cracks, residue, or contamination, and the specifications and dimensions of the grease cup holder shall conform to those shown in C of Figure 1. Replace if necessary.
  • 6.1.5 Insert an empty test tube and a thermometer (5.1.4) into each test tube hole and thermometer hole of the aluminum block furnace, respectively. According to Table 1, select the lowest furnace temperature for the test under the condition that the measured dropping point of the sample is not higher than the maximum dropping point corresponding to that furnace temperature.
  • 6.1.6 Select and use the test tube and accessories (E-1, E-2, and E-3 in Figure 1) so that thermometer swing is minimized. All components used before the test shall be at room temperature. As shown in F of Figure 1, assemble accessories successively onto the thermometer from accessory E-1 to accessory E-4. Adjust the bushing (5.3) and the bushing support ring (5.4) so that the bushing support ring is about 25 mm from the sensing bulb end of the thermometer. Place the grease cup holder (5.1.3) into the test tube (5.1.2). Insert the thermometer depth gauge (5.5) and the thermometer assembly into the test tube. Adjust the thermometer so that its sensing bulb end fits into the grease cup gauge. Adjust the bushing and the thermometer clamp (5.2) so that the shoulder of the bushing presses against the rim of the test tube opening.
• 6.2 Sample testing
  • 6.2.1 See Section 7 for sample preparation.
  • 6.2.2 Remove the thermometer assembly and the thermometer depth gauge from the test tube, place the grease cup on the grease cup holder in the test tube, and reinstall the thermometer assembly. The position of the thermometer need not be adjusted again, because at this time there is already an appropriate spacing between the sensing bulb end of the thermometer and the cup opening.
  • 6.2.3 Remove the empty test tube from the aluminum block furnace and gently insert it into the test tube assembly (G in Figure 1); ensure the test tube assembly is vertical in the grease cup holder.
    • Note: If the grease cup is tilted, the thermometer sensing bulb may contact the grease film, which will cause errors in the results.
  • 6.2.4 When the first drop of sample falls from the grease cup, leaves the cup mouth and reaches the bottom of the test tube, record the sample temperature and furnace temperature at this time, accurate to 1 ℃. For certain types of grease, such as those containing single soap components or special types of polymers, a drop with a tail may form; record the temperature when the grease drop falls to the bottom of the test tube as the observed dropping point.

9. Qualitative and Quantitative and Calculation Formulas

• Calculate the sample dropping point D according to formula (1):
  • D = t + (T − t) / 3 ………………(1)
  • Where:
    • D—— dropping point, in degrees Celsius (℃);
    • t—— the temperature when the first drop of sample falls from the grease cup to the bottom of the test tube, in degrees Celsius (℃);
    • T—— the temperature of the aluminum block furnace when the sample drops, in degrees Celsius (℃).
• Expression of results (Chapter 8): Report the dropping point from the result obtained in Chapter 7, accurate to 1 ℃.
• Terms (Chapter 3):
  • 3.1 Dropping point: The dropping point is a numerical value assigned to the composition of a grease, indicating the temperature at which the first drop of grease falls from the grease cup and reaches the bottom of the test tube; this temperature value requires correction.
  • 3.2 Grease: A stable product ranging from semi-fluid to solid formed by dispersing a thickener in a liquid lubricant.
  • 3.3 Observed dropping point: The temperature displayed by the thermometer when the first drop of grease falls from the grease cup to the bottom of the test tube.
  • 3.4 Thickener: In grease, a substance that disperses fine particles in the liquid lubricant to form a skeleton structure.

10. Precision

• Judge the reliability of test results according to the following provisions (95% confidence level).
• Note: To obtain accurate values, if the dropping point of the grease is lower than 221 ℃, use a thick-walled heat-resistant glass test tube; if the dropping point of the grease is higher than 221 ℃, use a thin-walled test tube.
• 9.1 Repeatability: The difference between two consecutive test results obtained by the same operator using the same instrument under the same operating conditions on the same sample shall not exceed the requirements of Table 2.
• 9.2 Reproducibility: The difference between two independent test results obtained by different operators in different laboratories on the same sample under the specified test conditions shall not exceed the requirements of Table 2.
• Table 2 Precision values:
  • Dropping point range <116 ℃: repeatability 6 ℃, reproducibility 9 ℃
  • Dropping point range 116 ℃~221 ℃: repeatability 8 ℃, reproducibility 12 ℃
  • Dropping point range 222 ℃~277 ℃: repeatability 6 ℃, reproducibility 16 ℃
  • Dropping point range 278 ℃~304 ℃: repeatability 7 ℃, reproducibility 12 ℃
  • Dropping point range 305 ℃~330 ℃: repeatability 18 ℃, reproducibility 24 ℃
• Note: In Table 2, “222~277” is as in the original text (corresponding to “277” in Table 1), requires confirmation against the source standard (source-text extraction).

11. Report

• Chapter 10 Test report: The test report shall contain at least the following information:
  • a) State that this standard is referenced;
  • b) Sample type and identification method;
  • c) Test results (see Chapter 8);
  • d) State any differences from the specified test procedure by agreement or otherwise;
  • e) Test date.

12. Normative References

• GB/T 514 Technical conditions for liquid-in-glass thermometers for petroleum product testing
• GB/T 4929 Determination of dropping point of lubricating grease
• ISO 6299:1998 Determination of dropping point of lubricating grease (wide temperature range) (English version) (modified 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.

14. Quick Reference Q&A