GB/T 12578-1990 Determination of lubricating oil flowability (U-shaped tube method)

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Card type: Test method

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

• Standard number: GB/T 12578-90
• Chinese full title: Determination of lubricating oil flowability (U-shaped tube method)
• English name: Lubricating oil - Determination of flow ability - U-tube method (the original title in English is “Lubricating oll -Determ Inatlon of flow abillty-U-tube method”, there is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Replacement relationship: not provided in the available source
• Reference adoption: Federal Republic of Germany national standard DIN 51568-74 “Determination of lubricating oil flowability (U-shaped tube method)” (see additional notes)
• Approval/implementation: approved by the State Bureau of Technical Supervision 1990-12-14, implemented on 1991-10-01

2. Scope of application and non-applicability

• Scope of application: This standard specifies the method for determining the flow properties of lubricating oils using a U-shaped tube; it is applicable to the determination of lubricating oils.
• Non-applicability: no explicit non-applicability clause is provided in the available source.
• Note: There is no relationship whatsoever between the flowability of a sample measured by this standard and its pour point or viscosity.

3. Method principle

Under constant pressure and specified low-temperature conditions, determine the rising speed of the lubricating oil in a U-shaped tube, and express it as the temperature at which the rising speed under these conditions is 10 mm/min, with the unit being ℃.

4. Reagents and materials (purity / preparation)

• Dry ice (3.2.1)
• Anhydrous ethanol: chemically pure (3.2.2)
• Petroleum ether: 60~90℃, analytically pure (3.2.3)
• Anhydrous sodium sulfate or anhydrous calcium chloride: used for dehydration when the sample contains water (4.1)
• Preparation method: not provided in the available source

5. Apparatus and equipment

• Test apparatus: as shown in Figure 1 (3.1.1). Labels in the figure: 1, 2, 3— stopcock; 4—U-shaped tube manometer; 5— iron block; 6— water bath; 7— glass funnel; 8— cold bath; 9, 12—U-shaped test tube; 10— stirrer; 11— thermometer.
• U-shaped test tube (3.1.2): as shown in Figure 2. The material is heat-resistant borosilicate glass, and the tube is marked with graduations divided in millimeters (mm); the dimensions of the bent portion of the U-shaped test tube shall allow a ball with a diameter of 5.5 mm to pass through smoothly; the volume of the U-shaped test tube up to the mark (×) shall not exceed 3.8 mL, and when reaching the mark at 50 mm it shall not exceed 7.2 mL. Figure 2 labeled dimensions (source-text extraction): φ6±0.3, wall thickness 1.2±0.15, 185±1, 7±0.5, 62±0.1, 65±0.1 (some values require confirmation against the source standard (source-text extraction)).
• Thermometer (3.1.3): -80–20℃, scale division 0.1℃; 0–100℃, scale division 1℃, one of each. (The original text “80–20C” is suspected to be “-80–20℃”, requires confirmation against the source standard (source-text extraction))
• Cold bath (3.1.4): a Dewar flask with an observation window, whose volume shall be such that when the U-shaped test tube is placed in the cold bath, it is at least 10 mm from the wall of the cold bath, and the meniscus of the test sample in the U-shaped test tube shall be at least 40 mm below the coolant level in the cold bath. The U-shaped test tube and thermometer are fixed vertically in the cold bath by a support and clamp. A stirrer shall be installed in the cold bath. Other cooling devices capable of accurately adjusting the temperature and meeting the above conditions with an accuracy of ±0.2℃ may also be used.
• Adjustable-speed electric stirrer (3.1.5)
• Pressure generator (3.1.6): place an inverted glass funnel weighted with an iron block into a container filled with water. Adjust the height of the water level so that the pressure generated in the glass funnel is 980±10 Pa (100±1 mmH₂O). Other pressure-generating devices capable of producing a pressure of 980±10 Pa may also be used.
• Glass funnel (3.1.7): diameter 120 mm.
• Pipette (3.1.8): 5 mL.
• Glass four-way connector (3.1.9): with three branch tubes, each branch tube having a glass stopcock, and the other branch tube connected to a U-shaped tube manometer (see Figure 1).
• Stopwatch (3.1.10): scale division 0.1 s.
• Microporous glass crucible (3.1.11): pore size 40~90 μm.

6. Recommended operating conditions

• Pressure: 980±10 Pa (100±1 mmH₂O) (3.1.6, 4.4, 5.2)
• Cold bath temperature control accuracy: ±0.2℃ (3.1.4)
• Cooling rate: about 1℃/min (5.1)
• Initial constant temperature: when cooled to 0℃, hold constant temperature for 15 min (5.1)
• After reaching the test temperature: maintain for at least 10 min (5.1)
• Stopwatch timing interval: start the stopwatch when the meniscus reaches the 0 mark, and stop the stopwatch when the meniscus passes a certain mm graduation after about 50~70 s (5.3)
• Range of rising speeds for three tests: approximately 20–30 mm/min, 6–15 mm/min, 2~5 mm/min (6.1)

7. Sampling and sample preparation

• The sample is filtered through a microporous glass crucible (if the sample contains water, first dehydrate with anhydrous sodium sulfate or anhydrous calcium chloride). Then heat the sample to 50℃, maintain for 15 min, and then cool to room temperature for use (4.1).
• Note: For high-viscosity lubricating oils, heating may be carried out before filtration, and the heating temperature shall not exceed 80℃ (4.1 note).
• The U-shaped test tube is first cleaned with petroleum ether, then rinsed once with anhydrous ethanol, and then naturally dried (4.2).
• Use a pipette to measure the sample and inject it into the U-shaped test tube up to the mark (×). The glass tube wall above the mark (×) shall not be contaminated with sample. For the same sample, fill three U-shaped test tubes in total, and place them vertically in a beaker for use (4.3).

8. Analysis procedure

• Install the test apparatus: fix the glass four-way connector on the support, connect the U-shaped tube manometer and pressure generator with rubber tubing (as shown in Figure 1), and adjust the pressure to 980±10 Pa (100±1 mmH₂O) (4.4).
• After adding anhydrous ethanol and the U-shaped test tube containing the sample to the cold bath, start the stirrer to stir, add dry ice to cool, and when the temperature drops to 0℃, hold constant temperature for 15 min, then continue cooling to the test temperature. The cooling rate is about 1℃/min, and when the test temperature is reached, maintain for at least 10 min (5.1).
• Open stopcocks 1 and 2, connect stopcock 1 to the U-shaped test tube filled with sample, close stopcocks 1 and 2, open stopcock 3 and adjust the water level so that the pressure is maintained at 980±10 Pa (100±1 mmH₂O) (5.2).
• Open stopcock 1; when the meniscus of the sample in the U-shaped test tube reaches the 0 mark, start the stopwatch; when the meniscus passes a certain millimeter (mm) graduation after about 50~70 s, stop the stopwatch and record the rising height and the time required (s). Then convert to the rising speed at mm/min. Perform the same procedure for the samples in the other two U-shaped test tubes at other temperatures (5.3).

9. Qualitative and quantitative determination and calculation formula

• Draw the characteristic curve: For each sample, three tests shall be carried out at not very different temperatures according to the procedure in Chapter 5, obtaining three rising speeds respectively, with ranges approximately 20–30 mm/min, 6–15 mm/min, and 2~5 mm/min. Use the rising speed as the ordinate and the test temperature as the abscissa. Use these three sets of data to draw a characteristic curve of temperature versus rising speed on graph paper, and obtain from the curve the temperature at which the rising speed is 10 mm/min (only interpolation may be used, not extrapolation); this temperature is expressed as the lubricating oil flowability (6.1).
• Example (N46 refrigeration oil):
  • Test temperature -34.7℃, rising speed 3.4 mm/min
  • Test temperature -29.6℃, rising speed 8.5 mm/min
  • Test temperature -19.0℃, rising speed 26.6 mm/min
  • From the ordinate of Figure 3, find the point where the rising speed is 10 mm/min; from this point draw a horizontal line intersecting the curve at point A; from point A draw a vertical line intersecting the abscissa at -28℃; this point is the lubricating oil flowability result, -28℃.
• Calculation formula: not provided in the available source (obtained by graphical interpolation; no calculation formula is given).

10. Precision

Judge the reliability of the test results according to the following provisions (95% confidence level):

• Repeatability: the difference between two results obtained by the same operator in repeated determinations shall not exceed 2℃ (7.1).
• Reproducibility: the difference between two results submitted by different laboratories shall not exceed 3℃ (7.2, the original number source-text extraction is “1.2”, requires confirmation against the source standard (source-text extraction)).

11. Report

Take the arithmetic mean of two results from repeated determinations as the sample result (8).

12. Referenced documents

• DIN 51568-74 “Determination of lubricating oil flowability (U-shaped tube method)” (reference adoption, see additional notes)
• Other referenced documents: not provided in the available source

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