GB/T 7325-1987 Determination of Evaporation Loss of Lubricating Greases and Lubricating Oils

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 7325-87 (the original cover shows GB 7825-87, the text page header shows GB 7325-87, requires confirmation against the source standard (source-text extraction))
• Chinese name: Determination of Evaporation Loss of Lubricating Greases and Lubricating Oils
• English name: Petroleum products - Lubricating greases and oils - Determination of evaporation loss
• Replacement relationship: From the date of implementation of this standard, the former China Petrochemical Corporation ministerial standard SY 4026-84 "Determination of Evaporation Loss of Lubricating Oils" is void
• Adoption relationship: This standard was formulated with reference to the American Society for Testing and Materials standard ASTM D 972 (the original shows "ASTW D SP2-5 (⑧)", requires confirmation against the source standard (source-text extraction)) "Determination of Evaporation Loss of Lubricating Greases and Lubricating Oils"
• UDC: UDC.9T1.S2:20 (requires confirmation against the source standard (source-text extraction))

2. Scope of application and non-applicability

• Applicable to the determination of evaporation loss of lubricating greases and lubricating oils. Evaporation loss of these lubricants is an important factor during use.
• The evaporation loss can be determined at any temperature from 99 to 150℃.
• Not applicable: not provided in the available source.

3. Method principle

Place the lubricant sample in the evaporator, put it in a constant-temperature bath at the specified temperature, and hot air passes over the surface of the sample 22h. Calculate the evaporation loss based on the weight loss of the sample.

4. Reagents and materials (purity / preparation)

• Air: clean air, capable of supplying the flow rate required by the evaporator. To obtain satisfactory results, air can be filtered by filling a tube of diameter 25.4mm and length 406mm with glass wool.
• Other reagents: not provided in the available source.

5. Apparatus and equipment

• 2.1 Evaporator: as described in Appendix A (supplementary provision).
• 2.2 Air supply system: capable of supplying clean air at the flow rate required by the evaporator; to obtain satisfactory results, air can be filtered by filling a tube of diameter 25.4mm and length 406mm with glass wool.
• 2.3 Oil bath: as described in Appendix A (supplementary provision). Note: If the heat capacity and thermal gradient characteristics are comparable to an oil bath, other constant-temperature baths may also be used.
• 2.4 Thermometer: as described in Appendix B (supplementary provision). Note: If the test temperature exceeds 150℃, a thermometer with a range of 0 to 360℃ and a scale division of 1℃ may be used.
• 2.5 Flowmeter: a calibrated rotameter, supplying air at a rate of 2.58±0.02 g/min from 15 to 30℃ (2L/min at standard temperature and standard pressure). The flowmeter should be as shown in Figure 1, equipped with a needle valve.
• Appendix A Equipment (supplementary provision):
  • A.1 Evaporator and its accessories: shall conform to the dimensional tolerances indicated in Figure 1, Figure 2, and Figure 3, and be able to be supported vertically in the oil bath.
  • A.1.1.1 The main body and cover of the evaporator shall be made of stainless steel, and the serpentine tube for heating air shall be made of tinned copper tube.
  • A.1.1.2 Sample cup (each with a maximum weight of 20g, the original shows "203", requires confirmation against the source standard (source-text extraction)), cover, exhaust tube, and outlet seat shall be made of alloy steel containing 18% chromium and 8% nickel (the original "[garbled alloy-element names]" requires confirmation against the source standard (source-text extraction)); the sample cup, cover, and exhaust tube are connected by threads, facilitating sample loading and weighing.
  • A.1.1.3 Evaporator base (the original "[garbled evaporator-base wording]", requires confirmation against the source standard (source-text extraction)).
  • A.2 Oil bath: of sufficient depth to allow the evaporator to be immersed to an appropriate level and to be controlled at the required temperature (±0.5℃); use a pump or stirrer to circulate the heating medium so that the maximum temperature difference at any point in the oil bath is 0.5℃ (the original "0.S[unreadable unit]", requires confirmation against the source standard (source-text extraction)). After the evaporator is immersed in the oil bath, the oil bath shall have sufficient heat capacity to bring the oil bath medium to the required temperature within 30min. The oil bath shall be provided with a thermometer hole so that the thermometer used can be inserted to the appropriate immersion depth. Adjust the oil bath so that there is no gradient or large fluctuation in temperature around the evaporator. Note: If the test temperature exceeds 150℃, the oil bath can be controlled at the required temperature (±1℃).
• Appendix B Thermometer specifications (supplementary provision):
  • Temperature range 95 to 103℃: total immersion; scale division 0.1℃; long lines indicate 0.5; numbers indicate 1℃; maximum error of scale value 0.1℃; the expansion portion may be heated to 156℃; total length 270 to 280mm; rod diameter 6.0 to 8.0mm; mercury bulb length 25 to 35mm; bulb diameter not less than 5.0, not greater than the rod diameter; distance from the bottom of the bulb to the 95℃ line 135 to 150mm; scale portion length 70 to 100mm; distance from the bottom of the bulb to the 155℃ line not provided in the available source.
  • Temperature range 95 to 155℃: total immersion; scale division 0.2℃; long lines indicate 2℃; numbers indicate 0.2℃ (requires confirmation against the source standard (source-text extraction)); maximum error of scale value 0.2℃; the expansion portion may be heated to 180℃; total length 374 to 384mm; rod diameter 7.0 to 8.0mm; mercury bulb length 10 to 20mm; bulb diameter 6.0 to 7.0mm; distance from the bottom of the bulb to the 95℃ line 115 to 135mm; scale portion length 324 to 344mm; distance from the bottom of the bulb to the 155℃ line not provided in the available source.
• Figure 1 Evaporator and accessories: 1— bath wall; 2— support rod; 3— rotameter; 4— needle valve; 5— ring groove cover; 6— sample cup assembly. Note: Unless otherwise specified, the tolerance for all dimensions is ±0.4mm.
• Figure 2 Lubricating grease sample cup assembly: 1— cover; 2— sample cup. Note: Unless otherwise specified, the tolerance for all dimensions is ±0.4mm.
• Figure 3 Lubricating oil sample cup assembly: 1— cover; 2— sample cup. Note: Unless otherwise specified, the tolerance for all dimensions is ±0.4mm.

6. Recommended operating conditions

• Test temperature: any temperature from 99 to 150℃; controlled to ±0.5℃ (when the test temperature exceeds 150℃, the oil bath can be controlled at ±1℃).
• Air flow rate: 2.58±0.02 g/min (2L/min at standard temperature and standard pressure), indicated by a calibrated rotameter from 15 to 30℃.
• Test time: 22h±5min.
• The evaporator shall be maintained in the constant-temperature bath for at least 30min before starting the test, during which clean air is passed through.
• Maximum temperature difference at any point in the oil bath 0.5℃.

7. Sampling and sample preparation

• Lubricating grease: Weigh the cleaned sample cup and cover (Figure 2) to the nearest 1mg. Remove the cover, fill the grease cup with lubricating grease, taking care to prevent air from being mixed in, scrape the lubricating grease with a straight-edge scraper so that it is level with the edge of the grease cup, wipe off any lubricating grease left on the edge or threads of the grease cup with a clean cotton yarn, and screw the cover tightly onto the grease cup without disturbing the scraped level surface of the lubricating grease. Weigh the assembly and record the net weight of the sample to the nearest 1mg.
• Lubricating oil: Weigh the cleaned sample cup and cover (Figure 3) to the nearest 1mg, transfer 10.00±0.05g of oil sample into the sample cup with a pipette, assemble the sample cup and cover carefully so that the sample does not splash onto the inner surface of the cover, weigh the assembly and record the net weight of the sample to the nearest 1mg.

8. Analytical procedure

• Lubricating grease:
  • 3.1 Weigh the cleaned sample cup and cover (Figure 2) to the nearest 1mg. Remove the cover, fill the grease cup with lubricating grease, taking care to prevent air from being mixed in, scrape the lubricating grease with a straight-edge scraper so that it is level with the edge of the grease cup, wipe off any lubricating grease left on the edge or threads of the grease cup with a clean cotton yarn, and screw the cover tightly onto the grease cup without disturbing the scraped level surface of the lubricating grease. Weigh the assembly and record the net weight of the sample to the nearest 1mg.
  • 3.2 Put on the lid (without the cover and sample cup), immerse the evaporator in the constant-temperature bath to reach the test temperature (controlled to ±0.5℃), as shown in Figure 1. Before starting the test, let the evaporator remain in the constant-temperature bath for at least 30min, during which clean air is passed through the evaporator at the specified rate of 2.58±0.02 g/min (2L/min at standard temperature and standard pressure), the air flow rate being indicated by the rotameter. Then remove the lid, screw on the weighed cover and grease cup, put the lid back on, tighten the three knurled cap screws, and seal the screws to prevent air from leaking under the lid. Clean air passes through the evaporator for 22h±5min.
  • 3.3 After 22h is completed, remove the assembled sample cup and cover from the evaporator, cool to room temperature, then weigh and record the net weight of the sample to the nearest 1mg.
• Lubricating oil:
  • 4.1 Weigh the cleaned sample cup and cover (Figure 3) to the nearest 1mg, transfer 10.00±0.05g of oil sample into the sample cup with a pipette, assemble the sample cup and cover carefully so that the sample does not splash onto the inner surface of the cover, weigh the assembly and record the net weight of the sample to the nearest 1mg.
  • 4.2 Carry out the procedure as described in 3.2 and 3.3.

9. Qualitative and quantitative determination and calculation formula

The evaporation loss of the sample X (expressed as weight %) is calculated according to the following formula:

X = (S - W) / S × 100

Where:

• X—— evaporation loss of the sample, %;
• S—— weight of the sample before the test, g;
• W—— weight of the sample after the test, g.

(The original formula is typeset as a fraction, source-text extraction appears as "S- / X=- / S / [unreadable symbol]×100", arranged according to context, requires confirmation against the source standard (source-text extraction))

10. Precision

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

• 6.1 Repeatability: For the same operator, using the same instrument, under the specified operating conditions, the difference between two repeated determination results for the same sample and their average shall not be greater than 2.5% of the average.
• 6.2 Reproducibility: For two operators, in two laboratories, for the same sample, under the specified operating conditions, the difference between the two results obtained and their average shall not be greater than 10% of the average.

11. Report

Take the arithmetic mean of two parallel determination results as the determination result. (The source text has “half-line determination”; requires confirmation against the source standard (source-text extraction))

12. Referenced documents

• Appendix A (supplementary element) Equipment
• Appendix B (supplementary element) Thermometer specifications
• Refer to ASTM D 972 (the source text has “ASTW D SP2-5 (⑧)”; requires confirmation against the source standard (source-text extraction))
• Replace SY 4026-84

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 Q&A reference