NB/SH/T 0874-2013 Crude petroleum and liquid petroleum products — Laboratory determination of density — Weighing digital liquid density meter method

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Card type: Test method

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

• Method number: NB/SH/T 0874—2013
• Chinese full title: Crude petroleum and liquid petroleum products — Laboratory determination of density — Weighing digital liquid density meter method
• English title: Crude petroleum and liquid petroleum products—Laboratory determination of density—Weighing digital liquid density meter method
• Replacement relationship: not provided in the available source (the foreword does not list a replaced standard)
• Publication/implementation: published on 2013-06-08, implemented on 2013-10-01
• Issuing body: National Energy Administration
• Custodian: Subcommittee on Static and Light Hydrocarbon Metering of Petroleum, National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280/SC2)
• Drafting organizations: responsible drafting by Sinopec Research Institute of Petroleum Processing; participating in drafting were Sinopec Beijing Yanshan Branch, PetroChina Daqing Oilfield Exploration and Development Research Institute, Petroleum Industry Crude Oil and Petroleum Product Quality Supervision and Inspection Center, Sinopec Beijing Petroleum Branch, and Qiqihar Test Precision Instrument Co., Ltd.
• Main drafters: Wei Jinxiang, Bo Yanhong, He Qijun, Zhao Jingbo, Li Jicheng, Zeng Fanming, Zhao Wanshan, Sun Yan

2. Scope of application and non-applicability

• Applicable: method for determining the standard density of liquid crude petroleum, petroleum products, and mixtures of petroleum products and non-petroleum products in the laboratory using a weighing digital liquid density meter (weighing-type density meter).
• Applicable: determination of crude petroleum and liquid petroleum products with a Reid vapor pressure (RVP) less than 100 kPa.
• Applicable: determination of liquids with sufficient fluidity. For liquids that are solid or not easily flowable at room temperature, a suitable constant-temperature bath may be used to measure the density of these liquids at a temperature above room temperature.
• Applicable: weighing-type density meters calibrated with a calibration liquid at 20 °C and for which the apparent density is not corrected for thermal expansion of the float during actual measurement.
• Note (original note): Crude petroleum may contain free water, suspended water, and sediment. When this standard is used to measure the density of volatile or waxy crude petroleum containing such substances, the measurement accuracy may be lower than the precision given in Chapter 12; the sample homogenization techniques given in Chapter 7 can maximize the representativeness of the transferred test portion.
• Not applicable: no explicitly listed non-applicable clauses are provided in the available source.

3. Method principle

The main components of the weighing-type density meter include a force sensor, a float, a suspension wire, a temperature sensor, a data processing and display instrument, and a density measuring cylinder. The float, connected to the force sensor by the suspension wire, is statically immersed in the test portion. According to Archimedes' principle, a change in the density of the test portion is converted into a change in the buoyant force exerted by the test portion on the float. The force sensor senses this change in buoyant force through the suspension wire and converts it into an electrical signal. The display instrument receives and processes the electrical signal and displays the density of the test portion on the display instrument.

According to the actual needs of density measurement, the test portion is heated or cooled so that it reaches the test temperature and has sufficient fluidity; the test portion is poured into the density measuring cylinder and stirred thoroughly so that the temperature of the test portion is uniformly distributed; the float is immersed and kept static in the test portion, and after the reading stabilizes, the apparent density and test temperature displayed by the weighing-type density meter are quickly read and recorded. The standard density is converted using petroleum measurement tables (or a weighing-type density meter with petroleum measurement tables embedded). When a stable temperature is required, especially when the difference between the test temperature and the ambient temperature is large, the density measuring cylinder should be placed in a constant-temperature bath or a density measuring cylinder capable of maintaining constant temperature should be used to contain the test portion.

4. Reagents and materials (purity / preparation)

• No reagents and materials chapter is provided in the available source (this standard does not list chemical reagents or preparation requirements).
• Requirements for related materials/components are given in Chapter 5 Apparatus (the float material and manufacturing process comply with the provisions of SH/T 0316—1998).

5. Apparatus and equipment

• 5.1 Weighing-type density meter: composed of a force sensor, a float, a suspension wire, a temperature sensor, a data processing and display instrument, and a density measuring cylinder. It can display density and temperature values on the display. The measuring range can meet actual needs, wherein the resolution of density measurement is not lower than 0.05 kg/m³, and the accuracy is not lower than (the original text here is missing source-text extraction, requires confirmation against the source standard (source-text extraction)); the resolution of temperature measurement is not lower than 0.01 °C, and the accuracy is not lower than ±0.1 °C.
• 5.1.1 Force sensor: capable of sensing and measuring (the original wording is incomplete, requires confirmation against the source standard (source-text extraction)) the change in tension transmitted to the suspension wire and converting this change in tension into an electrical signal. According to different conversion principles, it may be a resistance-type, capacitance-type, piezomagnetic-type, or other type of force sensor, and the overall force-measuring accuracy should meet the density measurement accuracy requirements of the weighing-type density meter.
• 5.1.2 Float: has a lifting lug at the top, and the lower part is preferably made into a conical cylinder. The selected material and manufacturing process comply with the provisions of SH/T 0316—1998, with an outer diameter of 20 mm～30 mm and a length of 80 mm～100 mm. When a lead-shot wax-sealed float is used above 38 °C, the lead-shot part should face downward, and it should be dried vertically and cooled.
• 5.1.3 Density measuring cylinder: may be made of glass, plastic, or metal. Its inner diameter is at least 25 mm larger than the outer diameter of the float (5.1.2), and its height should be such that when the float of the density meter is immersed in the test portion, the distance between the bottom of the float and the bottom of the cylinder is at least 25 mm, and the actual sample volume is not less than 300 mL. For pouring and adding (the original wording is incomplete, requires confirmation against the source standard (source-text extraction)), the front edge of the measuring cylinder should have a pouring lip.
• 5.1.4 Data processing and display instrument: has data processing and display functions, can receive and process signals from the force sensor and temperature sensor, and display the apparent density and test temperature of the test portion. According to user needs, the display instrument also has density conversion and test report preparation and printing functions.
• 5.1.5 Temperature sensor: a resistance-type or semiconductor-type temperature sensing element, with a suitable protective sleeve, sealing its connection with the wire to prevent intrusion of the test portion, and capable of meeting the temperature measurement range, resolution, and accuracy of the weighing-type density meter.
• 5.2 Constant-temperature bath: its size can accommodate the measuring cylinder, and the test portion can be completely immersed below the liquid surface of the constant-temperature bath. During the test, the temperature can be controlled within ±25 °C (original text as such, requires confirmation against the source standard (source-text extraction)). If the density measuring cylinder cannot be placed in the constant-temperature bath, a specially made density measuring cylinder may be used, with circulating water provided by the constant-temperature bath to ensure constant temperature of the test portion.
• 5.3 Glass stirring rod: diameter 5 mm～7 mm, length about 300 mm.

6. Recommended operating conditions

• Selection of test temperature (7.2.1): it should ensure that the sample to be tested reaches sufficient fluidity. For samples that require heating to have sufficient fluidity, they should be heated to the lowest temperature at which they can flow sufficiently, but the temperature must not be so high as to cause loss of light components, nor so low as to cause precipitation of wax in the sample.
• Note 1: At or near the standard temperature, the density or standard density measured by this method is the most accurate.
• Note 2: When the measured density is used for metering bulk oil products, under the premise of sufficient fluidity, selecting to measure density at or near the oil product temperature within ±3 °C can reduce the error in volume correction of the oil product.
• 7.2.2 For crude petroleum samples, a relatively higher temperature should be selected for density measurement at 20 °C, above the pour point by 9 °C or more, or above the cloud point by 3 °C or more.
• Note: For opaque viscous crude petroleum, insert a glass tube or glass rod into the sample; after removal, the inserted part should have good transparency, indicating that the sample already has sufficient fluidity.
• Environmental conditions (8.4): The weighing-type density meter (especially the density measuring cylinder) should be placed in a location without air flow. During the test, the change in ambient temperature should not exceed 2 °C; otherwise, the density measuring cylinder should be placed in a constant-temperature bath to avoid excessive temperature changes of the test portion.
• Installation of temperature sensor (8.5): As shown in Figure 1, fix the temperature sensor of the weighing-type density meter inside the measuring cylinder. Its temperature-sensing point should be located, in the horizontal direction, at the middle position of the distance from the inner wall of the measuring cylinder to the outer wall of the float, and in the vertical direction, at the middle position of the sample height, but the distance to the outer wall of the float should be at least 5 mm.

7. Sampling and sample preparation

• 6 Sampling: take samples in accordance with GB/T 4756 or GB/T 27867.
• Note: When taking volatile liquid samples, attention should be paid to the loss of light components caused by liquid volatility, and its impact on the accuracy of density measurement should be minimized.
• 7.1 Sample homogenization: sample homogenization is a necessary step to ensure that the transferred sample represents the overall sample as much as possible. During homogenization operations, care should always be taken to maintain the integrity of the sample.
• Note: For volatile crude petroleum or petroleum products containing water or sediment, as well as waxy volatile crude petroleum and petroleum products, loss of light components may occur during sample homogenization or heating.
• Treating samples of different properties by the methods given in Article 7.1.1 to Article 7.1.4 can reduce the loss of light components.
• 7.1.1 RVP Volatile crude petroleum and petroleum products with a value greater than 50 kPa: homogenize the sample in the original sample container and closed system.
• Note: Homogenizing volatile samples in an open container will cause loss of light components, thereby affecting the measured density value.
• 7.1.2 Waxy crude petroleum: If the pour point of the crude petroleum is higher than 10 °C or the cloud point is higher than 15 °C, before homogenization, the sample should be preheated to above the pour point by 9 °C or more, or above the cloud point by 3 °C or more, and the sample should be homogenized in the original sample container and closed system.
• 7.1.3 Waxy distillate oil: Before homogenization, the sample should be preheated to above the cloud point by 3 °C or more, and the sample should be homogenized in the original sample container and closed system.
• 7.1.4 Residual fuel oil: Before homogenization, the sample should be preheated to the test temperature (see Article 7.2.1 and its Note 2).
• 7.2 Test temperature: see Section 6 Recommended operating conditions.

8. Analytical procedure

• 8 Instrument preparation
  • 8.1 The density measurement part of the weighing-type density meter should be periodically verified/calibrated using a standard density meter or standard substance density traceable to national standards, and should be within the valid period of verification.
  • 8.2 The temperature measurement part of the weighing-type density meter should be periodically verified/calibrated using a standard thermometer traceable to national standards, and should be within the valid period of verification/calibration.
  • 8.3 Clean and dry the density measuring cylinder and float, and adjust them to near the test temperature.
  • 8.4 The weighing-type density meter (especially the density measuring cylinder) should be placed in a location without air flow. During the test, the change in ambient temperature should not exceed 2 °C; otherwise, the density measuring cylinder should be placed in a constant-temperature bath to avoid excessive temperature changes of the sample.
  • 8.5 As shown in Figure 1, fix the temperature sensor of the weighing-type density meter inside the measuring cylinder. Its temperature-sensing point should be located, in the horizontal direction, at the middle position of the distance from the inner wall of the measuring cylinder to the outer wall of the float, and in the vertical direction, at the middle position of the sample height, but the distance to the outer wall of the float should be at least 5 mm.
  • 8.6 Perform self-check and other preparations before density measurement in accordance with the operating requirements of the weighing-type density meter.
• 9 Measurement
  • 9.1 Transfer the sample at the test temperature into a density measuring cylinder that is basically at the same temperature as the sample, has stable temperature, and has a clean surface. During this process, avoid sample splashing and bubble formation, and minimize the volatilization of light components.
  • Note: If the temperature difference between the sample and the density measuring cylinder is relatively large, stabilizing the temperature may take a long time, inevitably causing excessive loss of light components from the sample and affecting the density measurement result.
  • 9.2 Observe the sample in the density measuring cylinder and wait until all bubbles have risen to the surface of the sample. When the oil product has high viscosity or poor fluidity, the bubbles in the sample rise slowly, and the waiting time may be long; when necessary, appropriately increase the sample temperature.
  • 9.3 Insert the stirring rod into the sample and make a vertical rotating motion to slowly stir the sample (see Figure 1) so that the temperature distribution of the sample in the measuring cylinder becomes uniform. Observe the displayed temperature value. When the temperature fluctuation within 30 s does not exceed 0.1 °C, read and record the sample temperature, and remove the stirring rod.
  • 9.4 Slowly lower the float of the weighing-type density meter into the sample and repeatedly raise and lower it in the sample 2 times to 3 times, finally allowing it to become completely still and immersed in the sample. Observe the density and temperature indications of the weighing-type density meter. After they are basically stable, repeatedly raise and lower the float in the sample again 2 times to 3 times, and again allow it to become still and immersed in the sample. For viscous liquids, it may be necessary to wait for the float to slowly sink into the liquid. During this period, the float of the density meter must not touch the density measuring cylinder or the temperature probe, and the suspension wire of the float must always remain taut. If it becomes slack, this indicates that the fluidity of the sample may be insufficient, and the test temperature should be appropriately increased until this phenomenon no longer occurs.
  • Note 1: When the temperature difference between the float and the sample is relatively large, temperature equilibration between the two may take a long time, inevitably causing loss of light components. Repeatedly raising and lowering the float in the sample helps achieve temperature equilibration as quickly as possible.
  • Note 2: For viscous opaque oil products, when the float is lifted, the float should have good transparency, thereby indicating that the sample has sufficient fluidity.
  • 9.5 Observe the sample and float in the measuring cylinder. When all bubbles in the sample have risen to the surface, the float is still, and the suspension wire is taut, continue to observe the density and temperature indications of the weighing-type density meter. When the density fluctuation within 30 s does not exceed 0.05 kg/m³ and the temperature fluctuation does not exceed 0.05 °C, read and record the density and temperature indications.
  • Note: For volatile oil products, all preparations should be made well and the density measurement should be completed in the shortest possible time to reduce the impact of light component loss on the measurement result.
  • 9.6 Compare the sample temperatures measured in 9.3 and 9.5. If the difference between the two sample temperatures is greater than 0.5 °C, reread the density and temperature indications in accordance with 9.3 to 9.5 until the temperature change stabilizes within 0.5 °C. If a stable temperature cannot be obtained, place the density measuring cylinder in a constant-temperature bath or use another constant-temperature method, and repeat the operation from Clause 9.3.
• Figure 1 Description: 1— density measuring cylinder; 2— stirring rod; 3— float; 4— suspension wire; 5— force sensor; 6— support guide frame; 7— temperature sensor; 8— data processing and display instrument.

9. Qualitative and Quantitative and Calculation Formulas

• 10.1 Overview: The apparent density and test temperature measured by the weighing-type density meter can be corrected and converted to standard density and density at other temperatures according to the following steps. The weighing-type density meter usually has a data processing function and can automatically complete the correction of apparent density and test temperature as well as the conversion to standard density and other densities.
• 10.2 Test temperature: After applying relevant corrections to the temperature indication read and recorded in 9.3, record it to the nearest 0.01 °C as the test temperature for density measurement by this method.
• 10.3 Apparent density: After applying relevant corrections to the density indication read and recorded in 9.5, record it to the nearest 0.05 kg/m³ as the apparent density for density measurement by this method.
• 10.4 Standard density: According to the test temperature in 10.2 and the apparent density in 10.3, consult the standard density table of the petroleum measurement tables corresponding to the test sample in GB/T 1885—1998 (crude oil—Table 59A, products—Table 59B, and lubricating oil—Table 59D) to convert the standard density of the test sample.
• 10.5.1 Due to the thermal expansion of the float, the apparent density usually cannot represent the sample density at the test temperature. Only when the test temperature is equal to the standard temperature (the sample temperature at which the density meter was calibrated) is the sample density equal to the apparent density. When the test temperature is not equal to the standard temperature, the density of the sample at the test temperature can be calculated according to formula (1):
  • ρt = ρ't [1 + αf (20 − t)] (1)
  • Where: ρt—— density of the sample at temperature t (test temperature); ρ't—— apparent density of the sample at test temperature t; αf—— volume expansion coefficient of the float (usually 25×10⁻⁶ °C⁻¹); t—— test temperature.
• 10.5.2 For the density of the sample at other temperatures, it can be calculated from the standard density and that temperature according to formula (2):
  • ρt = ρ20 × VCF20 (2)
  • Where: ρt—— density of the sample at temperature t; ρ20—— standard density of the sample; VCF20—— volume correction factor of the sample at temperature t (obtained from temperature t and standard density in the corresponding volume correction factor table of the petroleum measurement tables in GB/T 1885—1998).
• 11 Report the result: Take the arithmetic mean of the two density measurement results as the final density result, and report it to 0.1 kg/m³ (or 0.0001 g/cm³), 20 °C (the "204" at the end of the original text is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).

10. Precision

The reliability of the density measurement results of this method shall be judged according to the following provisions (confidence level 95%).

12.1 Repeatability: In the same laboratory, by the same operator using the same instrument, and according to the same method, under normal and correct operation on the same sample, the difference between two consecutive determination results shall not exceed the value in Table 1.

Table 1 Repeatability of Petroleum Product Density

(Note: The original layout of Table 1 source-text extraction is disordered. The above correspondence is organized according to the legible content of the original text. The specific values and row correspondence require confirmation against the source standard (source-text extraction).)

12.2 Reproducibility: In different laboratories, by different operators using different instruments, and according to the same method, under normal and correct operation on the same sample, the difference between the total test results obtained shall not exceed the value in Table 2.

Table 2 Reproducibility of Petroleum Product Density

Note: The standard does not provide density data for test temperatures exceeding the ranges specified in Table 1 and Table 2. When the test temperature exceeds the corresponding temperature range, the precision data in Table 1 and Table 2 are for reference only.

Note: The precision data in Table 1 and Table 2 were obtained using a weighing-type density meter with a maximum permissible error of 0.2 kg/m³. When the maximum permissible error of the weighing-type density meter is greater than 0.2 kg/m³, its precision results are expected to be equal to or lower than the data in Table 1 and Table 2; when the maximum permissible error of the weighing-type density meter is less than 0.2 kg/m³, its precision results are expected to be equal to or higher than the data in Table 1 and Table 2. (The original text "9.24em" is suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction))

11. Report

The 13 test report shall include at least the following:

• a) Name of the test sample;
• b) Standard number;
• c) Test results (see 11);
• d) Apparent density and test temperature;
• e) Other circumstances different from this method;
• f) Test date and test personnel.

12. Normative References

Normative references (Chapter 2):

• GB/T 1885—1998 Petroleum measurement tables
• GB/T 2013—2010 Determination of density of liquid petroleum and chemical products
• GB/T 4756 Manual sampling of petroleum liquids
• GB/T 27867 Automatic sampling of petroleum liquids by pipeline
• SH/T 0316—1998 Specification for petroleum hydrometers

Bibliography:

• [1] GB/T 1884—1998 Standard test method for density of crude petroleum and liquid petroleum products (glass hydrometer method)
• [2] Sinopec Research Institute of Petroleum Processing. Standardization research on measuring oil density using a weighing-type digital liquid density meter, Beijing, 2010 year 8 month
• [3] JJG 999—2005 Weighing-type digital liquid density meter

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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