GB/T 4929-1985 Determination of Dropping Point of Lubricating Grease

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

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

• Standard number: GB 4929-85
• Chinese full title: Determination of Dropping Point of Lubricating Grease
• English name: Lubricating grease — Determination of dropping point
• Replacement relationship: not provided in the available source
• Adoption relationship: This standard equivalently adopts the international standard draft recommendation ISO/DP 2176—1979 "Determination of Dropping Point of Lubricating Grease"
• Publication/implementation: issued by the National Bureau of Standards on 1985-02-06, implemented on 1985-10-01

2. Scope of application and non-applicability

• Scope of application: This method is applicable to the determination of the dropping point of lubricating grease.
• Non-applicability: not provided in the available source.

3. Method principle

This method consists of placing lubricating grease into the grease cup of a dropping point apparatus and, under specified standard conditions, determining the temperature at which the lubricating grease reaches a certain fluidity during the test.

4. Reagents and materials (purity / preparation)

• Oil for oil bath: composed of a 600 mL beaker and suitable oil (2.4.1). Purity/grade not provided in the available source.
• Other reagents: not provided in the available source.

5. Apparatus and equipment

• 2.1 Grease cup: chrome-plated brass cup, dimensions as shown in Figure 1 (the source contains Figure 1, source-text extraction dimensional data doubtful: wall taper angle 4°, 28, 120, $.82 - etc., requires confirmation against the source standard (source-text extraction)).
• 2.2 Test tube: rimmed heat-resistant borosilicate glass test tube, with three indentations around the circumference for supporting the grease cup, whose positions and dimensions are as shown in Figure 2.
• 2.3 Thermometer: partial immersion, meeting the specification requirements shown in Appendix A (supplementary document).
• 2.4 Accessories:
  • 2.4.1 Oil bath: composed of a 600 mL beaker and suitable oil.
  • 2.4.2 Ring stand and ring: used to support the oil bath.
  • 2.4.3 Thermometer clamp.
  • 2.4.4 Cork stopper: as shown in Figure 2.
  • 2.4.5 Polished metal rod: diameter 1.2~1.6 mm, length 150 mm.
  • 2.4.6 Heater: preferably heated by an immersion resistance heater regulated by a controlled voltage.
  • 2.4.7 Stirrer.
• Figure 2 Components of the assembled apparatus: 1— thermometer; 2— vent notch on the cork stopper; 3— cork guide ring, total clearance between ring and test tube 1.5 mm; 4— test tube; 5— grease cup.

6. Recommended operating conditions

• Heating rate (first stage): stir the oil bath, raise the temperature at a rate of 4~7 ℃/ min until the oil bath temperature reaches a temperature about 17 ℃ lower than the expected dropping point.
• Heating rate (second stage): reduce the heating rate so that before the oil bath temperature rises by a further 2.5 ℃, the difference between the temperature in the test tube and the oil bath temperature is within the range of 2 ℃ or lower than 2 ℃.
• Heating rate (third stage): continue heating, heating the oil bath at a rate of 1–1.5 ℃/ min, so that the difference between the temperature in the test tube and the temperature in the oil bath is maintained between 1–2 ℃.
• Oil level position: the oil level shall be no more than 6 mm from the edge of the test tube.
• Thermometer immersion: align the 76 mm immersion mark on the thermometer with the lower edge of the cork stopper, and immerse the assembly to this point.
• Thermometer bulb position: the top of the thermometer bulb shall be about 3 mm from the bottom of the grease cup; suspend a second thermometer in the oil bath so that its bulb is at approximately the same horizontal level as the bulb of the thermometer in the test tube.

7. Sampling and specimen preparation

• 3.2 Remove the grease cup, and press the large opening of the grease cup into the sample until the cup is filled with sample, taking as much care as possible to avoid working the sample (original text as such, suspected to be "stirring", requires confirmation against the source standard (source-text extraction)). Remove excess sample with a spatula. Holding the grease cup at the vertical position of the small hole at the bottom, gently hold the cup and push the polished metal rod downward until the rod protrudes about 25 mm. Press the rod against the grease cup in such a way that it contacts the upper and lower circular edges of the cup. Maintaining such contact, rotate the grease cup on the rod with the index finger so that it moves downward in a spiral. In this way, the sample adhering to the rod in a conical shape is removed, and when the grease cup finally slides off the end of the rod, a smooth grease film of reproducible thickness should remain on the inside of the grease cup.
• Note: Because the inner surface of the grease cup is coated with a grease film, the thermometer bulb must not contact the sample.

8. Analytical procedure

• 3.1 When assembling the test apparatus, as shown in Figure 2, fit the two cork stoppers onto the thermometer, and adjust the position of the upper cork stopper so that the top of the thermometer bulb is about 3 mm from the bottom of the grease cup. Suspend a second thermometer in the oil bath so that its bulb is at approximately the same horizontal level as the bulb of the thermometer in the test tube.
  • Note: The position of the top of the thermometer bulb in the test tube is not critical, as long as it does not block the small hole of the grease cup.
• 3.2 Specimen loading (see Section 7).
• 3.3 Place the grease cup and thermometer into the test tube, and hang the test tube in the oil bath. The oil level shall be no more than 6 mm from the edge of the test tube. The cork stopper in the test tube for fixing the thermometer shall be appropriately selected so that the 76 mm immersion mark on the thermometer aligns with the lower edge of the cork stopper. Immerse the assembly to this point.
• 3.4 Stir the oil bath and heat according to the heating program in Section 6. As the temperature continues to rise, the sample gradually emerges from the hole of the grease cup. When the 1th drop of fluid drips from the hole of the grease cup, immediately record the temperatures on both thermometers.
  • Note ①: For certain greases, such as some molybdenum-based greases, the fluid dripping out upon melting is always in the form of a thread, which may break or may remain until it drops to the bottom of the test tube; in the latter case, record the temperature when the fluid reaches the bottom of the test tube.
  • Note ②: For some greases, especially those containing molybdenum soap, the dropping point decreases with aging, and this change in dropping point is much greater than the allowable error of results obtained in different laboratories; therefore, interlaboratory comparison tests must be completed within six days.
• 3.5 If two specimens have approximately the same dropping point, they may be determined simultaneously in the same oil bath.

9. Qualitative and quantitative determination and calculation formula

• Reported value: the average of the temperature readings of the oil bath thermometer and the thermometer in the test tube is taken as the dropping point of the specimen (Chapter 5).
• Calculation formula: not provided in the available source.

10. Precision

The following provisions are used to judge the reliability of the results (95% confidence level):

• 4.1 Repeatability: for repeated determinations by the same operator on the same instrument for the same specimen, the difference between the two results shall not exceed ?℃ (original value missing, requires confirmation against the source standard (source-text extraction)).
• 4.2 Reproducibility: for determinations by different operators in different laboratories on the same specimen, the difference between the results they respectively submit shall not exceed 13 ℃ (original text as such, suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).

11. Report

The average of the temperature readings of the oil bath thermometer and the thermometer in the test tube is taken as the dropping point of the specimen.

12. Referenced documents

• Appendix A Thermometer specification (supplementary document)
• ISO/DP 2176—1979 "Determination of Dropping Point of Lubricating Grease" (equivalently adopted)

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