GB/T 12579-2002 Determination of Foaming Characteristics of Lubricating Oils

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Card type: Test method

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

• Standard number: GB/T 12579-2002
• Chinese name: Determination of Foaming Characteristics of Lubricating Oils
• English name: Determination of foaming characteristics of lubricating oils
• Replacement relationship: replaces GB/T 12579-1990
• Adoption relationship: equivalent adoption of ISO 6247:1998 'Petroleum products—Determination of foaming characteristics of lubricating oils' (eqv ISO 6247:1998)
• First issued: 1990 year

2. Scope of application and non-applicability

• 1.1 This standard specifies a method for determining the foaming characteristics of lubricating oils at moderate temperatures. It is applicable to lubricating oils with or without additives used to improve or suppress the tendency to form stable foam.
• Note (1.1): In high-speed gears, large-volume pumping and splash lubrication systems, the tendency of lubricating oils to generate foam is a serious problem; the resulting poor lubrication, cavitation and overflow loss of lubricant can all lead to mechanical failure. This method is valuable in selecting oils suitable for these lubrication systems. The numerical values used to describe the foaming tendency and/or stability of lubricating oils are based on experimental evidence.
• 1.2 This standard involves certain hazardous materials, operations and equipment, but does not purport to address all safety problems. Therefore, users should establish appropriate safety and protection measures and formulate corresponding management systems before using this standard.
• Non-applicable scope: not provided in the available source.

3. Method principle

• 4 Method summary: The sample is blown with air at a constant flow rate for 5 min at 24 ℃, then allowed to stand for 10 min. At the end of each period, the volume of foam in the sample is measured. A second sample is taken and tested at 93.5 ℃; after the foam disappears, the test is repeated at 24 ℃.

4. Reagents and materials (purity / preparation)

• 6.1 Reagents
  • 6.1.1 n-Heptane: analytical reagent.
  • 6.1.2 Acetone: analytical reagent.
  • 6.1.3 Toluene: analytical reagent.
  • 6.1.4 Isopropanol: analytical reagent.
  • 6.1.5 Water: meets the grade three water requirements in GB/T 6682.
  • 6.1.6 Butyl phthalate: analytical reagent, used for the differential-pressure flowmeter. (The source text source-text extraction is 'butyl phthalate vinegar'; requires confirmation against the source standard (source-text extraction))
• 6.2 Materials
  • 6.2.1 Cleaning agent: non-ionic, water-soluble.
  • 6.2.2 Desiccant: color-indicating silica gel, dehydrated silica gel or other suitable material.
• Preparation method: not provided in the available source.

5. Apparatus and equipment

• 5.1 Foam test apparatus: see Figure 1, including the following accessories.
  • 5.1.1 Graduated cylinder: capacity 1 000 mL, minimum division 10 mL, distance from the inner bottom of the cylinder to the 1 000 mL mark is 335 mm～385 mm. Round mouth; if cut, it needs fine polishing. Note: When the graduated cylinder has a pouring spout, cut off the pouring spout part so that its top opening is round.
  • 5.1.2 Stopper: made of rubber or other suitable material, matching the round top opening of the above graduated cylinder. The center of the stopper should have two round holes, one for inserting the inlet tube and one for the outlet tube.
  • 5.1.3 Diffuser head: a sintered crystalline alumina sand core sphere with a diameter of 25.4 mm; or a cylindrical shape made of sintered 5 μm porous stainless steel. When measured according to the method specified in Annex A, it shall meet the following requirements:
    • Maximum pore diameter: not greater than 80 μm
    • Permeability: 3 000 mL/min～6 000 mL/min
    • Note: As shown in Figure 2, attach the diffuser head to the inlet tube by any convenient method.
• 5.2 Test bath: its dimensions are sufficient to immerse the graduated cylinder to the 900 mL mark and to maintain the bath temperature at the specified temperature ±0.5 ℃. The bath and bath liquid should be transparent so that the immersed graduated cylinder can be read.
  • Note 1: A hard borosilicate glass jar with a diameter of about 300 mm and a height of about 450 mm can meet the requirements. (The source text source-text extraction is 'borosilicate glass jar'; requires confirmation against the source standard (source-text extraction))
  • Note 2: The 93.5 ℃ bath should be placed in a sufficiently large transparent container to prevent breakage.
• 5.3 Air source: the air flow from the air source through the gas diffuser head can be maintained at 94 mL/min±5 mL/min. The air must also pass through a drying tower with a height of 300 mm; the drying tower should be filled in the following order: above the constriction of the drying tower, place 20 mm of absorbent cotton, 110 mm of desiccant, 40 mm of color-indicating silica gel, 30 mm of desiccant, 20 mm of absorbent cotton. When the color-indicating silica gel begins to change color, the drying tower must be refilled.
  • Note: Air that has been dried to a dew point of −60 ℃ or lower and has been tested (with a certificate of inspection) to contain no hydrocarbons need not pass through the drying tower.
• 5.4 Flowmeter: capable of measuring a flow rate of 94 mL/min±5 mL/min.
  • Note: When using a differential-pressure type flowmeter, the capillary diameter between the two arms of the U type tube is about 0.4 mm, height 16 mm; butyl phthalate is more suitable as the filling liquid (see Figure 1). (The source text source-text extraction is 'butyl phthalate vinegar'; requires confirmation against the source standard (source-text extraction))
• 5.5 Volume measuring device: capable of accurately measuring a gas volume of about 470 mL at a flow rate of 94 mL/min.
  • Note: A calibrated wet gas meter with a division value of 0.01 L may be used.
• 5.6 Timer: electronic or manual, with division value and accuracy of 1 s or higher.
• 5.7 Thermometer: mercury glass thermometer meeting the specifications of Annex B, or a fully immersed thermometer with a measuring range of 0 ℃～50 ℃ and 50 ℃～100 ℃, with a minimum division value of 0.1 ℃.
• Annex A Apparatus (determination of maximum pore diameter and permeability of gas diffuser head):
  • A2.1 Air source: an adjustable air source capable of providing clean, dry air.
  • A2.2 Liquid differential pressure gauge: U tube type, using water as the liquid, with sufficient length to display at least a pressure difference of 800 mm, or a calibrated pressure gauge with at least equivalent accuracy.
  • A2.3 Graduated cylinder: 250 mL, with sufficient height to immerse the diffuser head to a depth of 100 mm.
  • A2.4 Gas volume measuring instrument: used to measure gas volume, capable of measuring at least a flow rate of 6 000 mL/min. A back-pressure flowmeter should not be used.
  • A2.5 Suction filter flask: the mouth of the flask is large enough to accommodate the diffuser head, and it has a side arm. It should be fitted with a rubber stopper with a hole for inserting the inlet tube.

6. Recommended operating conditions

• Test temperature: Procedure I 24 ℃; Procedure II 93.5 ℃; Procedure III first 93.5 ℃ then cooled to 24 ℃.
• Air flow rate: 94 mL/min±5 mL/min.
• Blowing time: 5 min±3 s.
• Standing time: 10 min±10 s.
• Total volume of air passed through the system: 470 mL±25 mL.
• Bath temperature tolerance: specified temperature ±0.5 ℃.
• In 8.3, when the oil temperature reaches 93 ℃±1 ℃, insert the diffuser head and inlet tube.
• 8.1 Heat the sample to 49 ℃±3 ℃ and allow it to cool to 24 ℃±3 ℃.
• 8.5.1 Optional step A: sample temperature 18 ℃～32 ℃; after stirring, bring the oil temperature to 24 ℃±3 ℃.

7. Sampling and sample preparation

• 8.1 Without mechanical shaking or stirring, pour about 200 mL of sample into a 600 mL beaker, heat to 49 ℃±3 ℃, and allow it to cool to 24 ℃±3 ℃ (for samples stored for more than two weeks, see 8.5.1 optional step A).
• 8.5.1 Optional step A: Clean a 1 L container with a high-speed stirrer according to the procedure in 7.2, add 18 ℃～32 ℃ of 500 mL sample to this container, and stir at maximum speed for 1 min. During stirring, some air is often entrained, so it is necessary to let it stand to eliminate the introduced foam and bring the oil temperature to 24 ℃±3 ℃. Within 3 h after stirring, start the test according to 8.2.
• Other sampling requirements: not provided in the available source.

8. Analytical procedure

• 7 Preparation: After each test, the test graduated cylinder and inlet tube must be thoroughly cleaned to remove trace additives left from the previous test, as these additives can seriously affect the results of the next test.
  • 7.1 Cleaning of the graduated cylinder: First carefully clean the graduated cylinder with toluene, n-heptane and cleaning agent in sequence, then rinse with water and acetone, and finally blow dry the graduated cylinder with a clean, dry air stream. The inner wall of the graduated cylinder should drain cleanly without leaving water droplets.
  • 7.2 Cleaning of the gas diffusion head: Clean the diffusion head separately with toluene and n-heptane as follows: immerse the diffusion head in about 300 mL of solvent, and use vacuum and pressure to make part of the solvent pass back and forth through the diffusion head at least 5 times. Then thoroughly blow dry the inlet tube and diffusion head with clean, dry air. Finally, wipe the outside of the inlet tube with a clean cloth moistened with n-heptane, then wipe with a clean dry cloth, being careful not to touch the diffusion head.
  • 7.3 Instrument installation: Install the instrument as shown in Figure 1. Adjust the position of the inlet tube so that the gas diffusion head just contacts the center of the bottom of the graduated cylinder. The connection between the air inlet tube and the flowmeter should be made through a copper tube, and this copper tube should wrap around the inner wall of the cooling bath at least once to ensure that the volume of air can be measured at about 24 ℃. Check the system for leaks. Disconnect the inlet tube and outlet tube, and remove the stopper.
• 8.1 Sample pretreatment (see Section 7).
• 8.2 Procedure I:
  • Pour the sample into the graduated cylinder so that the liquid level reaches the 190 mL mark. Immerse the graduated cylinder in a 24 ℃ bath, immersing at least to the 900 mL mark, and secure it with a heavy metal ring to prevent it from floating. When the oil temperature reaches the bath temperature, insert the stopper, connect the diffusion head and the inlet tube not connected to the air source, and after the diffusion head has been soaked for about 5 min, connect the outlet tube to the gas volume measuring device, turn on the air source, and adjust the air flow rate to 94 mL/min±5 mL/min. The air passing through the gas diffusion head is required to be clean and dry. Start timing from the appearance of the first bubble from the gas diffusion head, and aerate for 5 min±3 s. Immediately record the foam volume (i.e., the total volume minus the liquid volume), to the nearest 5 mL. The total volume of air passing through the system should be 470 mL±25 mL. Disconnect the hose from the flowmeter and shut off the air source. Allow the graduated cylinder to stand for 10 min±10 s, and record the foam volume again, to the nearest 5 mL.
• 8.3 Procedure II:
  • Pour the second sample into a clean graduated cylinder so that the liquid level reaches the 180 mL mark. Immerse the graduated cylinder in a 93.5 ℃ bath, immersing at least to the 900 mL mark. When the oil temperature reaches 93 ℃±1 ℃, insert a clean gas diffusion head and inlet tube, and carry out the test according to the procedure described in clause 8.2, recording the foam volume at the end of the aeration period and at the end of the static period, respectively, to the nearest 5 mL.
• 8.4 Procedure III:
  • Destroy the foam generated after the test in clause 8.3 by stirring. Place the test graduated cylinder at room temperature, allow the sample to cool to below 43.5 ℃, then place the graduated cylinder in a bath at 24 ℃. When the sample temperature reaches the bath temperature, insert a clean inlet tube and diffusion head, carry out the test according to the procedure described in clause 8.2, and record the foam volume at the end of the aeration period and at the end of the static period, respectively, to the nearest 5 mL.
  • Note: If it is a viscous oil, standing for 3 h may not be sufficient to eliminate bubbles; it may be allowed to stand longer, but the time must be recorded and noted in the results.
• 8.5 Some types of lubricating oils may, during storage, exhibit increased foaming due to changes in the dispersibility of the foam inhibitor. If such a phenomenon is suspected, the following optional procedure A may be used.
  • 8.5.1 Optional procedure A: see Section 7.
• 9 Simplified test procedure: For routine testing, a simplified test procedure may be used. This test procedure differs from the standard method in only one respect. The air passes through the gas diffusion head, and the total volume of air blown in within 5 min is not measured, which eliminates the volume measuring device and the necessary airtight connection from the graduated cylinder to the volume measuring device, but requires that the flowmeter be calibrated and that the flow rate be strictly controlled.
• Appendix A Test procedure:
  • A3.1 Maximum pore diameter determination
    • A3.1.1 Connect the fitting shown in Figure 2 (but without the brass tube) and a tube of length 1.0 m and inner diameter 8 mm to the air source, and immerse the clean diffusion head in the liquid in the graduated cylinder to a depth of 100 mm (100 mm refers to the distance from the top of the diffusion head to the liquid surface), soaking for at least 2 min. If the diffusion head is non-metallic, the liquid in the graduated cylinder is water; if the diffusion head is metallic, the liquid in the graduated cylinder is isopropanol. Connect the inlet tube to the air source (A2.1), and increase the air pressure at a rate of about 490 Pa/min (50 mmH₂O/min) until the first moving bubble emerges from the diffusion head and rises in the water or isopropanol.
      • Note: A moving bubble is the first bubble of a continuously emerging string of bubbles.
    • A3.1.2 Read the water level positions on the two arms of the manometer and record their difference p.
      • Note: Gradually increase the air pressure, and by observing the uniformity of the bubble flow distribution on the surface of the diffusion head, obtain the consistency of the pore distribution near the maximum pore diameter.
    • A3.1.3 The maximum pore diameter of the diffusion head Ds (μm) or Dm (μm) is calculated using formula (A1) or formula (A2) (see Section 9).
  • A3.2 Permeability determination: Connect the clean, dry diffusion head to the air source using a tube of length 1.0 m and inner diameter 8 mm, and place it in a suction flask. The suction flask is connected to a gas volume measuring device through a tube of length 0.5 m and inner diameter 8 mm (see Figure A2). Adjust the pressure difference to 2.45 kPa (250 mmH₂O), and measure the volume of gas flowing through the diffusion head per minute (mL) using the gas volume measuring device (A2.4).
    • Note: Depending on the sensitivity of the flowmeter used, a longer observation record may be made to obtain the average flow rate per minute.

9. Qualitative and quantitative determination and calculation formulas

• Foam volume reading: to the nearest 5 mL (in ISO 6247:1998, the foam volume reading is specified to the nearest 10 mL; in this standard, the foam volume reading is specified to the nearest 5 mL).
• Report results to the nearest 5 mL, expressed as "foam tendency" (foam volume at the end of the aeration period mL) and/or "foam stability" (foam volume at the end of the static period mL). Each result shall indicate the procedure number and whether the sample was tested directly or after stirring (optional procedure A).
• When the foam or bubble layer does not completely cover the oil surface, and clear oil in patches or "eyes" is visible, report the foam volume as "0 mL".
• Appendix A Maximum pore diameter calculation formulas:
  • Ds = 29 225 / (p − 100) ………………(A1)
  • Dm = 8 930 / (p − 80) ………………(A2)
  • Where:
    • Ds— maximum pore diameter of non-metallic diffusion head, μm;
    • Dm— maximum pore diameter of metallic diffusion head, μm;
    • p— difference in water levels between the two arms of the liquid manometer, mm.
• Precision calculation formulas:
  • Repeatability:
    • r (Procedure I and Procedure III) = 10 + 0.22X ………………(1)
    • r (Procedure II) = 15 + 0.33X ………………(2)
  • Reproducibility:
    • R (Procedure I and Procedure III) = 15 + 0.45X ………………(3)
    • R (Procedure II) = 35 + 1.01X ………………(4)
  • Where: X— average of two determination results, mL.

10. Precision

• Judge the reliability of the results according to the following provisions (95% confidence level).
• The precision of this standard is given in clauses 10.1 and 10.2, and is shown in Figures 3 and 4. For optional procedure A, precision has not yet been established.
• 10.1 Repeatability (r): The difference between two test results obtained by the same operator using the same instrument under constant test conditions on the same sample shall not exceed the values of formula (1) and formula (2).
  • r (Procedure I and Procedure III) = 10 + 0.22X ………………(1)
  • r (Procedure II) = 15 + 0.33X ………………(2)
  • Where: X— average of two determination results, mL.
• 10.2 Reproducibility (R): The difference between two independent test results obtained by different operators in different laboratories on the same sample shall not exceed the values of formula (3) and formula (4).
  • R (Procedure I and Procedure III) = 15 + 0.45X ………………(3)
  • R (Procedure II) = 35 + 1.01X ………………(4)
  • Where: X— average of two determination results, mL.

11. Report

• Report results to the nearest 5 mL, expressed as "foam tendency" (foam volume at the end of the aeration period mL) and/or "foam stability" (foam volume at the end of the static period mL). Each result shall indicate the procedure number and whether the sample was tested directly or after stirring (optional procedure A).
• When the foam or bubble layer does not completely cover the oil surface, and clear oil in patches or "eyes" is visible, report the foam volume as "0 mL".

12. Normative references

• GB/T 6682 Water specifications and test methods for analytical laboratory use
• ISO 6247:1998 "Petroleum products—Determination of foaming characteristics of lubricating oils" (equivalent adoption)
• Note: The clauses included in the following standards constitute a part of this standard by reference. Unless otherwise expressly specified in the standard, the following referenced standards shall be the currently effective standards.

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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