SH/T 0725-2002 Calculation Method for Carbon-Type Composition of Petroleum-Based Insulating Oils

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Card type: Test method

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

• Standard number: SH/T 0725-2002
• Chinese title: Calculation Method for Carbon-Type Composition of Petroleum-Based Insulating Oils
• English title: Standard test method for carbon-type composition of insulating oils of petroleum origin
• Replacement relationship: not provided in the available source (the foreword only states modified adoption of ASTM D2140-97, and does not mention replacement of an old standard number)
• Adoption relationship: modified adoption of ASTM D2140-97 "Standard Test Method for Carbon-Type Composition of Petroleum-Based Insulating Oils"
• Issued/implemented: issued on 2003-03-18, implemented on 2003-05-01
• Issuing body: State Economic and Trade Commission
• Secretariat: Sinopec Research Institute of Petroleum Processing
• Drafting organization: Refining Research Institute of Luoyang Petrochemical Engineering Corporation, China Petrochemical Corporation
• Main drafters: Wang Guiying, Hong Liyan, Wang Ou

2. Scope of application and non-applicability

• 1.1 specifies a method for calculating the carbon-type composition of mineral insulating oils by the basic physical constant correlation method.
• 1.2 is applicable to carbon-type composition analysis of samples with an average molecular weight of 200 to 600 and an aromatic hydrocarbon carbon atom number of 0 to 50. The carbon-type composition is expressed as: percentage composition of aromatic hydrocarbon carbon, percentage composition of naphthenic hydrocarbon carbon, and percentage composition of paraffinic hydrocarbon carbon. If the viscosity-gravity constant (VGC) and specific refraction (ri) of the sample are known, these compositions can be obtained from correlation chart 1. This method only requires determination of viscosity, density, relative density, and refractive index.
• 1.3 is applicable to carbon-type composition analysis for determining electrical insulating oils used in transformers and conducting cables. It is mainly used for new oils with or without inhibitors.
• 1.4 This standard is not intended to address all safety issues associated with its use. Users are responsible for establishing appropriate safety and protective measures before use and for determining applicable management systems.
• Non-applicability: no explicit non-applicability clauses are provided in the available source.

3. Method principle

• Chapter 4 Method summary: determine the viscosity, density, relative density, and refractive index of the sample, and use the given equations to calculate the viscosity-gravity constant (VGC) and specific refraction (ri) of the sample. On correlation chart 1, directly read the carbon atom percentage compositions of aromatic hydrocarbons, naphthenic hydrocarbons, and paraffinic hydrocarbons according to the values of VGC and ri, expressed as CA, CN, and CP respectively.
• Note: Figure 1 is a satisfactory correlation chart for this method. If it is ensured that the data obtained are consistent with Figure 1, a correlation chart better than Figure 1 may be designed and used.

4. Reagents and materials (purity / preparation)

• Not provided in the available source (this standard is a calculation method and does not list a reagents and materials section).

5. Instruments and equipment

• Chapter 6 Apparatus: this standard does not require special apparatus, but to obtain the VGC and ri parameters in Figure 1, the basic physical properties of the sample need to be determined. The apparatus required for these determinations is specified in detail in Chapter 7.
• Specific instruments: not provided in the available source (Chapter 7 only cites method standards and does not list a specific instrument list).

6. Recommended operating conditions

• Viscosity determination temperature: 37.8 ℃ (see 7.2)
• Density determination temperature: 20 ℃ (see 7.3)
• Reference temperature for relative density: 15.6 ℃ (see 7.3)
• Refractive index determination temperature: 20 ℃ (see 7.4)
• Other recommended operating conditions: not provided in the available source

7. Sampling and sample preparation

• 7.1 Sampling shall be carried out in accordance with method GB/T 4756 or GB 7597. The sample amount shall be sufficient to ensure all required determinations can be performed.
• Sample preparation: not provided in the available source.

8. Analysis procedure

• 7.2 Determine the viscosity of the sample at 37.8 ℃ in accordance with method GB/T 265.
• 7.3 Determine and calculate the density of the sample at 20 ℃ and the relative density at 15.6 ℃ in Table A1 in accordance with method SH/T 0604 or GB/T 2540 and GB/T 1885 and Appendix A.
• 7.4 Determine the refractive index of the sample at 20 ℃ in accordance with method SH/T 0724.

9. Qualitative and quantitative determination and calculation formulas

• 8.1 Based on the viscosity and relative density of the sample measured in clause 7.2 and clause 7.3, calculate the viscosity-gravity constant VGC of the sample according to formula (1):
  • VGC = (G + 0.0887 − 0.7761 log log(10V − 4)) / (1.082 − 0.721 log log(10V − 4))
  • Where: G— relative density of the sample at 15.6 ℃; V— viscosity of the sample at 37.8 ℃, mm²/s.
  • Note: In the original text of source-text extraction formula (1), some symbols are noisy (such as "[unreadable character]'" and "[unreadable sign]0.7761oglog"). The above formula has been organized according to context, requires confirmation against the source standard (source-text extraction).
• 8.2 Based on the density and refractive index of the sample measured in clause 7.3 and clause 7.4, calculate the specific refraction ri of the sample according to formula (2):
  • ri = n²₀ − (d/2)
  • Where: n²₀—refractive index of the sample at 20 ℃; d— density of the sample at 20 ℃, g/cm³.
  • Note: In the original text, source-text extraction is "r;=n[unreadable characters](d/2)", the symbols are noisy, requires confirmation against the source standard (source-text extraction).
• 8.3 Using the VGC and ri values obtained in clause 8.1 and clause 8.2, read the corresponding values of CA, CN, and CP from Figure 1.
• 8.4 For samples with sulfur content greater than or equal to 0.8%, to improve accuracy, corrections may be made using formula (3), formula (4), and formula (5):
  • Corrected CN = CN − S/0.288 ………………(3)
  • Corrected CP = CP + S/0.216 ………………(4)
  • Corrected CA = 100 − (corrected CN + corrected CP) ………………(5)
  • Where: S— mass fraction of sulfur content in the sample, %.
  • Note: The sulfur content of finished oils to which this standard applies is generally less than 0.8%, so correction is not necessary. However, for new oils, test oils, or when the sulfur content is unknown, it is recommended to determine the sulfur content by an appropriate method, such as GB/T 388 and other methods.
• Qualitative and quantitative determination: no other qualitative and quantitative descriptions are provided in the available source.

10. Precision

• 10.1 Precision: the precision of this standard was not determined by a single laboratory test. The precision of the three test data involved in this standard has been given in their respective determination methods, so the precision can be calculated from the precision of these data (excluding sulfur correction). At the same time, to avoid errors when using Figure 1, the procedure in Appendix B may be used for calculation. The reliability of the results is judged by the following provisions (95% confidence level).
• 10.1.1 Repeatability (r)): the difference between two test results obtained by the same operator using the same apparatus under the same operating conditions on the same sample shall not exceed the value specified in Table 1.
  • Table 1 Repeatability provisions Unit: %
    • CA=0: CA 0.2, CN 0.3, CP 0.3
    • CA=25: CA 0.1, CN 0.2, CP 0.2
    • CA=50: CA 0.1, CN 0.5, CP 0.5
• 10.1.2 Reproducibility (R)): the difference between two test results obtained by different operators in different laboratories on the same sample shall not exceed the value specified in Table 2.
  • Table 2 Reproducibility provisions Unit: %
    • CA=0: CA 0.2, CN 0.7, CP 0.5
    • CA=25: CA 0.2, CN 0.4, CP 0.4
    • CA=50: CA 0.2, CN 1.0, CP 1.1
• Note: The precision of carbon-type composition calculation varies with the position on the CA-CN-CP plane chart. If the content of CA is high, the test deviations of CN and CP are large. If density and refractive index are determined by routine methods rather than the methods specified in this standard, the precision values given above are not applicable.
• 10.2 Bias: because no suitable reference material is available for determining the bias of this standard, no statement of bias has been made.

11. Report

• 9.1 Percentage composition of aromatic hydrocarbon carbon atoms CA %;
• 9.2 Percentage composition of naphthenic hydrocarbon carbon atoms CN %;
• 9.3 Percentage composition of paraffinic hydrocarbon carbon atoms CP %.
• Note: The sum of the results of clause 9.1, clause 9.2, and clause 9.3 shall be 100%.

12. Referenced documents

• GB/T 265 Petroleum products—Determination of kinematic viscosity and calculation of dynamic viscosity
• GB/T 388 Determination of sulfur content in petroleum products (oxygen bomb method)
• GB/T 1885 Petroleum measurement tables
• GB/T 2540 Determination of density of petroleum products (pycnometer method)
• GB/T 4756 Petroleum liquids—Manual sampling
• GB 7597 Sampling method for power oils (transformer oil, turbine oil)
• SH/T 0604 Determination of density of crude petroleum and petroleum products (U-type vibrating tube method)
• SH/T 0607 Determination of hydrocarbon types in rubber extender oils, process oils and petroleum-derived oils (clay-silica gel adsorption chromatography)
• SH/T 0724 Determination of refractive index and refractive dispersion of liquid hydrocarbons
• SH/T 0729 Calculation method for carbon distribution and structural group composition of petroleum fractions (n—d—M method)
• Annex A (normative annex) Density conversion table
• Annex B (informative annex) Computer program for calculating carbon-type composition

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