GB/T 265-1988 Kinematic viscosity of petroleum products and calculation of dynamic viscosity

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Card type: Test method

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

• Standard number: GB 265-88
• Chinese title: Petroleum products — Determination of kinematic viscosity and calculation of dynamic viscosity
• English title: Petroleum products—Determination of kinematic viscosity and calculation of dynamic viscosity (the original title is spelled as "Petroleum oroducts-Deter mination of kinematic viscosity and calculation of dynamic viscosity", requires confirmation against the source standard (source-text extraction))
• Replacement relationship: replaces GB 265—83
• First issued: 1964 year 4 month 4 day (see additional notes)
• Approval/implementation: approved by China Petrochemical Corporation 1988-05-23, implemented 1989-04-01
• UDC 865.52/.58;: 582.13 (transcribed as in the original, requires confirmation against the source standard (source-text extraction))

2. Scope of application and non-applicability

• Applicable to the determination of the kinematic viscosity of liquid petroleum products (referring to Newtonian liquids), in units of m²/s, in practice usually mm²/s is used.
• Dynamic viscosity can be obtained by multiplying the measured kinematic viscosity by the density of the liquid.
• Note: The liquid measured by this method is considered to have a constant ratio of shear stress to shear rate, that is, viscosity is independent of shear stress and shear rate; such a liquid is called a Newtonian liquid.
• Not applicable: no explicit non-applicability clause is provided in the available source.

3. Method principle

At a certain constant temperature, measure the time for a certain volume of liquid to flow under gravity through a calibrated glass capillary viscometer; the product of the capillary constant of the viscometer and the flow time is the kinematic viscosity of the liquid measured at that temperature. At temperature t, the kinematic viscosity is denoted by the symbol ν_t. The product of the kinematic viscosity at that temperature and the density of the liquid at the same temperature is the dynamic viscosity of the liquid at that temperature. At temperature t, the dynamic viscosity is denoted by the symbol η_t.

4. Reagents and materials (purity / preparation)

• 2.2.1 Solvent naphtha: meets the NY-120 requirements in GB 1922 "Solvent naphtha", as well as suitable soluble solvents.
• 2.2.2 Chromic acid cleaning solution.
• 3.1 Petroleum ether: 60~90°C, chemically pure.
• 3.2 95% ethanol: chemically pure.
• Table 1 Constant-temperature bath liquid (selected according to the test temperature):
  • 50~100°C: transparent mineral oil, glycerol (glycerin), or 25% ammonium nitrate aqueous solution (a layer of transparent mineral oil will float on the surface of this solution)
  • 20~50°C: water
  • 0~20°C: a mixture of water and ice, or a mixture of ethanol and dry ice (solid carbon dioxide)
  • 0~-50°C: a mixture of ethanol and dry ice; in the absence of ethanol, unleaded gasoline may be used instead
  • Note: The mineral oil in the constant-temperature bath preferably contains an antioxidant additive to delay oxidation and extend service life.

5. Instruments and equipment

• 2.1.1 Viscometer:
  • 2.1.1.1 The glass capillary viscometer shall meet the requirements of SY 3607 "Technical specifications for glass capillary viscometers". Automatic viscometers with the same precision are also permitted.
  • 2.1.1.2 One set of capillary viscometers, with capillary inner diameters of 0.4, 0.6, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, and 6.0 mm (see the figure below).
  • 2.1.1.3 Each viscometer must be verified and its constant determined in accordance with JJG 155 "Verification regulation for working capillary viscometers".
  • Selection principle: select an appropriate viscometer according to the test temperature, ensuring that the flow time of the sample is not less than 200 s, and the flow time of a viscometer with an inner diameter of 0.4 mm is not less than 350 s.
• 2.1.2 Constant-temperature bath: with transparent walls or observation holes, height not less than 180 mm, volume not less than 2 L, equipped with an automatic stirring device and an electric heating device capable of accurately adjusting the temperature. When testing at 0°C and below 0°C, use a cylindrical transparent vacuum flask with a viewing window, with dimensions the same as the aforementioned transparent constant-temperature bath, and provided with a stirring device.
• 2.1.3 Glass mercury thermometer: meets GB 514 "Technical specifications for liquid thermometers for petroleum product testing", with a scale division of 0.1°C. When determining kinematic viscosity below -30°C, a glass alloy thermometer or other glass liquid thermometer with the same scale division value may be used.
• 2.1.4 Stopwatch: scale division of 0.1 s.
• The stopwatch, capillary viscometer, and thermometer used for viscosity determination must all be verified periodically.
• Capillary viscometer figure notes: 1, 6— tube body; 2, 3, 5— expansion sections; 4— capillary; a, b— marked lines (the original figure note source-text extraction is "1.6 one tube body: 2.3.5 one expansion section; 4 one capillary, 8, b one marked line", requires confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• The test temperature must be maintained constant to ±0.1°C.
• Table 2 Constant-temperature time of the viscometer in the constant-temperature bath:
  • 80, 100°C: 20 min
  • 40, 50°C: 15 min
  • 20°C: 10 min
  • 0~-50°C: 15 min
• The constant-temperature bath liquid is selected according to Table 1 and the test temperature.
• Thermometer installation: the mercury bulb is positioned close to the horizontal plane of the midpoint of the capillary, and the temperature scale is located 10 mm above the constant-temperature bath liquid surface.
• When a total-immersion thermometer is exposed above the liquid surface, calculate the correction value Δt according to formula (1): Δt = k·h(t₁-t₂), where k is a constant (for mercury thermometers take 0.00016, for alcohol thermometers take 0.0011), h is the height of the mercury column or alcohol column exposed above the bath surface (expressed in thermometer degrees), t₁ is the specified temperature for viscosity determination (°C), and t₂ is the air temperature near the exposed part of the thermometer liquid column (°C, measured with another thermometer). During the test, take t₁ minus Δt as the temperature reading on the thermometer.

7. Sampling and sample preparation

• 4.1 When the sample contains water or mechanical impurities, it must be dehydrated before the test, and mechanical impurities must be removed by filtration with filter paper.
• For lubricating oils with high viscosity, a porcelain funnel may be used, and suction filtration may be carried out using a water-jet pump or other vacuum pump, or dehydration and filtration may be carried out at a temperature of 50~100°C.
• 4.2 Before determination, the viscometer must be washed with solvent naphtha or petroleum ether; if contaminated with dirt, wash sequentially with chromic acid cleaning solution, water, distilled water, or 95% ethanol, then place in an oven to dry or blow dry with hot air filtered through cotton.
• 4.3 Sample loading: load the sample into a clean, dry capillary viscometer with an inner diameter meeting the requirements. Before loading, put a rubber tube on side tube 7, block the opening of tube body 6 with a finger, invert the viscometer, and insert tube body 1 into the container holding the sample; use a rubber bulb, water-jet pump, or other vacuum pump to draw the liquid up to marked line b, taking care not to cause bubbles or breaks in the liquid in tube body 1, expansion sections 2 and 3. After the liquid level reaches marked line b, lift the viscometer from the container, quickly restore it to its normal position, wipe off excess sample adhering to the outer wall of the end of tube body 1, and remove the rubber tube from side tube 7 and put it on tube body 1.
• 4.4 Immerse the viscometer containing the sample in a previously prepared constant-temperature bath, and fix it on a stand with a clamp; when fixing the position, the expansion section 2 of the capillary viscometer must be immersed halfway.

8. Analytical procedure

• 5.1 Adjust the viscometer to a vertical position, and check the verticality of the capillary from two mutually perpendicular directions using a plumb line. Adjust the constant-temperature bath to the specified temperature, immerse the viscometer loaded with the sample in the constant-temperature bath, and keep it at constant temperature for the time specified in Table 2. The test temperature must be maintained constant to ±0.1°C.
• 5.2 Using the rubber tube attached to the opening of tube body 1 of the capillary viscometer, draw the sample into expansion section 3 so that the sample liquid level is slightly above marked line a, taking care not to cause bubbles or breaks in the liquid in the capillary and expansion section 3.
• 5.3 Observe the flow of the sample in the tube body; start the stopwatch when the liquid level exactly reaches marked line a; stop the stopwatch when the liquid level exactly reaches marked line b. When the sample liquid level flows in expansion section 3, ensure that the liquid being stirred in the constant-temperature bath maintains a constant temperature, and no bubbles should appear in the expansion section.
• 5.4 The flow time recorded with the stopwatch shall be determined repeatedly at least four times, and the difference between each flow time and their arithmetic mean shall meet the following:
  • When determining viscosity at temperatures 100~15°C, the difference shall not exceed ±0.5% of the arithmetic mean;
  • When determining viscosity below 15~-30°C, the difference shall not exceed ±1.5% of the arithmetic mean;
  • When determining viscosity below -30°C, the difference shall not exceed ±2.5% of the arithmetic mean.
  • Then take the arithmetic mean of the flow times obtained from not less than three determinations as the average flow time of the sample.

9. Qualitative and quantitative determination and calculation formula

• 6.1 At temperature t, the kinematic viscosity ν_t (mm²/s) of the sample is calculated according to formula (2):
  • ν_t = C · τ_t
  • Where: C—— viscometer constant, mm²/s²; τ_t—— average flow time of the sample, s.
• Example (original text): the viscometer constant is 0.4780 mm²/s², the flow times of the sample at 50°C are 318.0, 322.4, 322.6 and 321.0 s, the arithmetic mean of the flow times is 321.0 s; the permissible difference between each flow time and the mean flow time is 321.0×0.5% = 1.6 s; the difference between 318.0 s and the mean flow time has exceeded 1.6 s, discard it; using 322.4, 322.6 and 321.0 s, the mean flow time is 322.0 s; the determined result of the kinematic viscosity of the sample is ν₅₀ = C·τ₅₀ = 0.4780×322.0 = 154.0 mm²/s.
• Calculation of the dynamic viscosity η_t of the sample at temperature t for 6.2:
  • 6.2.1 Determine the density ρ_t (g/cm³) of the sample at temperature t in accordance with GB 1884 "Petroleum and liquid petroleum products — Determination of density (hydrometer method)" and GB 1885 "Petroleum measurement tables".
  • At temperature t, the dynamic viscosity η_t (mPa·s) of the sample for 6.2.2 is calculated according to formula (3): η_t = ν_t · ρ_t (the original formula (3) source-text extraction is missing, completed according to context, requires confirmation against the source standard (source-text extraction))
  • Where: ν_t—— the kinematic viscosity of the sample at temperature t, mm²/s; ρ_t—— the density of the sample at temperature t, g/cm³.
• Appendix A (reference item) Table A1 Conversion table between kinematic viscosity and Engler viscosity (degrees of condition); Note: for higher kinematic viscosity (mm²/s), conversion shall be carried out according to the following formula: E_t = 0.135 ν_t (the original text is "E1=0.135Vt", requires confirmation against the source standard (source-text extraction)), where E_t is the Engler viscosity (degrees of condition) of the petroleum product at temperature t, and ν_t is the kinematic viscosity (mm²/s) of the petroleum product at temperature t.

10. Precision

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

• 7.1 Repeatability: the difference between two results obtained by the same operator on the same sample by repeated determination shall not exceed the following values:
  • Determination viscosity temperature (the temperature interval source-text extraction in the original table is incomplete, requires confirmation against the source standard (source-text extraction)): repeatability is 1.0% of the arithmetic mean
  • Below 15~-30°C: 3.0% of the arithmetic mean
  • Below -30~-60°C: 5.0% of the arithmetic mean
• 7.2 Reproducibility: the difference between two results submitted by different operators in two laboratories shall not exceed the following values:
  • Reproducibility is 2.2% of the arithmetic mean (the temperature interval source-text extraction in the original table is incomplete, requires confirmation against the source standard (source-text extraction))

11. Report

• For the numerical value of the viscosity determination result in 8.1, take four significant figures.
• In 8.2, take the arithmetic mean of two repeated determination results as the kinematic viscosity or dynamic viscosity of the sample.

12. Normative references

• SY 3607 "Technical specifications for glass capillary viscometers"
• JJG 155 "Verification regulation for working capillary viscometers"
• GB 514 "Technical specifications for liquid thermometers for petroleum product testing"
• GB 1922 requirements for NY-120 in "Solvent naphtha"
• GB 1884 "Petroleum and liquid petroleum products — Determination of density (hydrometer method)"
• GB 1885 "Petroleum measurement tables"

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