GB/T 1884-2000 Standard Test Method for Density of Crude Petroleum and Liquid Petroleum Products by Laboratory Determination (Hydrometer Method)

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Card type: Test method

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

• Standard number: GB/T 1884-2000
• Chinese full title: Standard Test Method for Density of Crude Petroleum and Liquid Petroleum Products by Laboratory Determination (Hydrometer Method)
• English title: Crude petroleum and liquid petroleum products — Laboratory determination of density — Hydrometer method
• Equivalent adoption: eqv ISO 3675:1998
• Replacement relationship: replaces GB/T 1884—1992
• First issued: 1980; revised in 1983; confirmed in 1992 (original foreword)
• Publication/implementation: published on 2000-04-03, implemented on 2000-07-01; issued by the State Bureau of Quality and Technical Supervision

2. Scope of application and non-applicability

• Applicable to the laboratory determination, using a glass petroleum hydrometer (hereinafter referred to as hydrometer), of the 20℃ density of crude petroleum, petroleum products, and mixtures of petroleum products and non-petroleum products that are normally liquid.
• Applicable to liquids with a Reid vapor pressure (RVP) less than 100 kPa.
• Applicable to the determination of the density of readily flowing transparent liquids; a suitable constant-temperature bath may also be used to determine viscous liquids at temperatures above room temperature; it can also be used for opaque liquids by reading the point where the upper meniscus of the liquid is tangent to the hydrometer stem, and correcting with Table 1.
• Since the hydrometer is calibrated for accurate reading at a specified temperature, the scale reading at other temperatures is only the hydrometer reading (called apparent density), not the density at that temperature.
• Note 1: The accuracy of determining the density of volatile or waxy crude petroleum containing free water or suspended water and sediment by this standard may be lower than the precision given in Chapter 13 (in the original note, where “Chapter 13” appears, source-text extraction shows “Chapter ?”, requires confirmation against the source standard (source-text extraction)).
• Note 2: The density value 20℃ may be converted to the corresponding density 15℃ using GB/T 1885 “Petroleum Measurement Tables”.
• Not applicable: no explicit “not applicable” clause is provided in the available source.

3. Method principle

Bring the sample to the specified temperature, pour it into a density measuring cylinder at approximately the same temperature, place a suitable hydrometer into the temperature-adjusted sample, and let it stand. After the temperature has reached equilibrium, read the hydrometer scale reading and the sample temperature. Use the petroleum measurement tables to convert the observed hydrometer reading to standard density. If necessary, place the density measuring cylinder together with the contained sample in a constant-temperature bath to avoid excessive temperature variation during the determination.

4. Reagents and materials (purity / preparation)

• No reagent and material clause is provided in the available source (this standard is a physical determination method and does not list reagents).
• Materials involved: clean filter paper (10.2, used to remove bubbles from the sample surface); damp cloth (10.9, used to wipe the outer wall of the plastic measuring cylinder to remove static electricity).

5. Apparatus and equipment

• 5.1 Density measuring cylinder: made of transparent glass, plastic, or metal, with an inner diameter at least 25 mm larger than the outer diameter of the hydrometer (5.2), and a height such that when the hydrometer floats in the sample, the distance between the bottom of the hydrometer and the bottom of the cylinder is at least 25 mm. A plastic density measuring cylinder shall not discolor and shall resist attack, shall not affect the characteristics of the material being tested; after long exposure to sunlight, it shall not become opaque. Note: For convenience in pouring, the edge of the density measuring cylinder should have a pouring lip.
• 5.2 Hydrometer: made of glass, shall comply with the technical requirements given in SH/T 0316 and Table 1.
• 5.3 Constant-temperature bath: its dimensions shall be such that it can accommodate the density measuring cylinder, completely immerse the sample below the surface of the constant-temperature bath liquid, and maintain the test temperature within ±0.25℃ during the test.
• 5.4 Thermometer: range, scale interval, and maximum scale error are given in Table 2.
• 5.5 Glass or plastic stirring rod: about 450 mm long.

Table 1 Technical requirements for hydrometers

Note: A SY-1 type or SY-Ⅱ type petroleum hydrometer may be used (in the original, source-text extraction is “SY-I type”, requires confirmation against the source standard (source-text extraction)).

Table 2 Technical requirements for thermometers

Note: A resistance thermometer may be used, provided its accuracy is not lower than the uncertainty of the above thermometers.

6. Recommended operating conditions

• Test temperature (7.2.1): heat the sample until it flows sufficiently, but the temperature shall not be so high as to cause loss of light components, or so low as to cause wax in the sample to precipitate.
  • Note 1: Determination by the hydrometer method is most accurate when the density is at or near the standard temperature 20℃ or 20℃.
  • Note 2: The hydrometer reading should be obtained at a temperature suitable for the physicochemical characteristics of the sample being tested, and this temperature is preferably close to the standard temperature 20℃. When the density value is used for bulk petroleum measurement, determining the density at or near the bulk petroleum temperature ±3℃ can reduce the error in petroleum volume correction.
• 7.2.2 For crude petroleum samples, heat to 20℃, or above the pour point by 9℃, or above the cloud point by 3℃, whichever is higher.
• Ambient temperature: during the entire test, the ambient temperature change shall not exceed 2℃; when the ambient temperature change exceeds ±2℃, a constant-temperature bath shall be used (10.3).
• Constant-temperature bath control: maintain the test temperature within ±0.25℃ during the test (5.3).
• Determination of temperature stability: record the temperature to within 0.1℃; if the difference between the temperature after the test and the temperature at the start of the test is greater than 0.5℃, reread the hydrometer and thermometer readings until the temperature change stabilizes within ±0.5℃ (10.13).

7. Sampling and sample preparation

• 6 Sampling: sampling shall be carried out in accordance with GB/T 4756. Note: When an automatic sampling method is used to take volatile liquids, unless a variable-volume sampler is used to take the sample and transfer it to the laboratory, loss of light components will occur and affect the accuracy of the density determination.
• 7.1 Sample mixing: mixing the sample is a necessary step to make the test sample represent the entire sample as much as possible, but during the mixing operation, care shall always be taken to maintain the integrity of the sample. Note: For volatile crude petroleum and petroleum products containing water or sediment, or waxy volatile crude petroleum and petroleum products, it should be recognized that loss of light components may occur during homogenization or heating of the sample. Using the methods given in 7.1.1~7.1.4 to handle samples of different properties can reduce the loss of light components.
  • 7.1.1 Volatile crude petroleum and petroleum products with RVP greater than 50 kPa: To reduce loss of light components, the sample should be mixed in the original container and in a closed system. Note: Mixing volatile samples in an open container will cause loss of light components and will affect the measured density value.
  • 7.1.2 Waxy crude petroleum: If the pour point of the crude petroleum is higher than 10℃ or the cloud point is higher than 15℃, before mixing the sample, heat to above the pour point by 9℃, or above the cloud point by 3℃. To reduce loss of light components, the sample should be mixed in the original container and in a closed system.
  • 7.1.3 Waxy distillate oil: Before mixing, the sample should be heated to above the cloud point 3℃.
  • 7.1.4 Residual fuel oil: Before mixing the sample, heat it to the test temperature (see 7.2.1 and its Note 2).

8. Analytical procedure

• 8 Instrument calibration
  • 8.1 The hydrometer shall be periodically calibrated using a standard hydrometer traceable to national standards or the density of a traceable standard substance, and shall be rechecked at least every five years.
  • 8.2 The thermometer shall be periodically calibrated using a standard thermometer traceable to national standards.
• 9 Instrument preparation
  • 9.1 Check the reference point of the hydrometer to determine whether the hydrometer scale is in the correct position within the stem; if the scale has moved, discard this hydrometer.
  • 9.2 Bring the temperature of the density measuring cylinder and hydrometer close to the temperature of the sample (see 7.2.1 and its Note 2).
• 10 Determination method
  • 10.1 At the test temperature (see 7.2.1), transfer the sample into a clean density measuring cylinder (5.1) at a stable temperature, avoiding splashing of the sample and formation of air bubbles, and reducing volatilization of light components.
  • 10.2 Use a piece of clean filter paper to remove all bubbles formed on the surface of the sample.
  • 10.3 Place the cylinder containing the sample vertically in a place free from air movement. During the entire test, the ambient temperature change shall not exceed 2℃. When the ambient temperature change exceeds ±2℃, a constant-temperature bath shall be used (5.3) to avoid excessive temperature variation (see 10.13).
  • 10.4 Use a suitable thermometer (see Table 2) or stirring rod (5.5) to stir the sample with a vertical rotating motion; if a resistance thermometer is used, use a stirring rod, so that the density and temperature of the sample throughout the cylinder become uniform. Record the temperature to within 0.1℃. Remove the thermometer or stirring rod from the density measuring cylinder.
  • 10.5 Place a suitable hydrometer (5.2) into the liquid, release it when it reaches the equilibrium position, and let the hydrometer float freely; be careful to avoid wetting the stem above the liquid surface. Push the hydrometer below the equilibrium point by 1 mm or 2 mm, and let it return to the equilibrium position, observe the meniscus shape; if the meniscus shape changes, clean the hydrometer stem and repeat this operation until the meniscus shape remains unchanged.
  • 10.6 For opaque viscous liquids, wait for the hydrometer to slowly sink into the liquid.
  • 10.7 For transparent low-viscosity liquids, push the hydrometer into the liquid about two scale divisions, then release it. Since excess liquid on the stem affects the reading, minimize residual liquid on the portion of the hydrometer stem above the liquid surface.
  • 10.8 When releasing, gently rotate the hydrometer so that it comes to rest and floats freely away from the cylinder wall. Allow sufficient time for the hydrometer to come to rest and for all bubbles to rise to the surface (see 10.2); remove all bubbles before reading.
  • 10.9 When using a plastic graduated cylinder, wipe the outer wall of the cylinder with a damp cloth to remove all static electricity. Note: Using a plastic graduated cylinder often generates static charges and may hinder the hydrometer from floating freely.
  • 10.10 When the hydrometer floats freely away from the cylinder wall and is at rest, read the hydrometer scale value according to 10.11 or 10.12, reading to the nearest 1/5 of the scale interval.
  • 10.11 For measuring transparent liquids, first position the eye slightly below the liquid surface, then slowly raise it to the surface; first an irregular ellipse is seen, which then becomes a straight line tangent to the hydrometer scale (see Figure 1). The hydrometer reading is the point where the lower meniscus of the liquid is tangent to the hydrometer scale.
  • 10.12 For measuring opaque liquids, position the eye slightly above the liquid surface for observation (see Figure 2). The hydrometer reading is the point where the upper meniscus of the liquid is tangent to the hydrometer scale.
    • Note 1: If a SY-1 type or SY-II type petroleum hydrometer is used, still read the scale at the point where the upper meniscus of the liquid is tangent to the hydrometer stem (the source text source-text extraction is "SY-1 pear or SY- 1 type", requires confirmation against the source standard (source-text extraction)).
    • Note 2: When using a metal density measuring cylinder to measure a completely opaque sample, ensure the sample liquid level is filled to within 5 mm from the top of the cylinder, so that the hydrometer reading can be read accurately.
  • 10.13 After recording the hydrometer reading, immediately carefully remove the hydrometer and stir the sample vertically with a thermometer. Record the temperature to the nearest 0.1℃; if this temperature differs from the initial test temperature by more than 0.5℃, re-read the hydrometer and thermometer readings until the temperature change stabilizes within ±0.5℃. If a stable temperature cannot be obtained, place the hydrometer cylinder and its contents in a constant-temperature bath and repeat the operation from 10.3.
  • 10.14 After a lead shot wax-sealed hydrometer has been used above 38℃, it shall be dried vertically and cooled.

9. Qualitative and Quantitative and Calculation Formulas

• 11.1 After applying relevant corrections to the observed thermometer reading, record to the nearest 0.1℃.
• 11.2 Since the hydrometer reading is calibrated according to the lower meniscus of the liquid, for opaque liquids, the observed hydrometer reading shall be corrected for the meniscus according to the meniscus correction values given in Table 1. Note: For special-purpose hydrometers, the correction value can be determined by testing; immerse this hydrometer in a transparent liquid with a surface tension similar to that of the test sample and observe the maximum height the liquid climbs on the hydrometer stem. The hydrometer meniscus correction values specified in this method are given in Table 1.
• 11.3 After applying relevant corrections to the observed hydrometer reading, record to 0.1 kg/m³ (0.000 1 g/cm³).
• 11.4 According to the different test oils, use Table 59A, Table 59B or Table 59D in GB/T 1885 to convert the corrected hydrometer reading to standard density at 20℃.
  • a) Crude oil: Table 59A;
  • b) Petroleum products: Table 59B;
  • c) Lubricating oils: Table 59D.
  • Note 1: To convert density from kg/m³ to g/cm³ or g/mL, divide by 10³.
  • Note 2: For mutual conversion between 20℃ density and 15℃ density, Table E1 and Table E2 in GB/T 1885 may be used.
• Calculation formula: not provided in the available source (table lookup conversion is used).

10. Precision

• 13.1 Repeatability: The difference between consecutive test results obtained by the same operator using the same instrument under constant operating conditions on the same test sample, correctly operated according to the test method, in long-term operating practice, will exceed the value shown in Table 3 only one time in twenty.

Table 3 Repeatability

• 13.2 Reproducibility: The difference between two independent results obtained by different operators in different laboratories on the same test sample, correctly operated according to the test method, in long-term operating practice, will exceed the value shown in Table 4 only one time in twenty.

Table 4 Reproducibility

• Note 1: For viscous crude oils and products, when the test temperature exceeds the range specified in 13.1 and 13.2, no precision data have been obtained.
• Note 2: The precision data given in 13.1 and 13.2 were obtained using hydrometers with a maximum permissible scale error of 0.6 kg/m³ (0.000 6 g/cm³); precision data for hydrometers with maximum permissible scale errors of 0.2 kg/m³ (0.000 2 g/cm³) and 0.3 kg/m³ (0.000 3 g/cm³) have not been obtained, but equal or higher precision is expected.

11. Report

• 12 Report results: The final density result shall be reported to 0.1 kg/m³ (0.000 1 g/cm³), 20℃.
• 14 Test report: The test report shall include at least the following:
  • a) Type and identification of the test substance;
  • b) National standard number;
  • c) Test results (see Chapter 12);
  • d) Hydrometer reading and corresponding test temperature;
  • e) Any circumstances different from those specified in this method;
  • f) Test date.

12. Normative References

• GB/T 1885 Petroleum measurement tables
• GB/T 4756 Manual sampling of petroleum liquids
• SH/T 0316 Specification for petroleum hydrometers
• ISO 3675:1998 (equivalent adoption)

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