GB/T 12576-1997 Calculation of vapor pressure, relative density, and octane number of liquefied petroleum gas

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Card type: Test method

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

• Standard number: GB/T 12576-1997
• Chinese name: Calculation of vapor pressure, relative density, and octane number of liquefied petroleum gas
• English name: Liquified petroleum gases—Calculation of vapour pressure and relative density and octane number
• Replacement relationship: replaces GB/T 12576—90
• Adoption relationship: equivalent adoption of ASTM D2598—91 "Calculation of certain physical properties of liquefied petroleum gas from composition analysis"
• First issued: 1990 year 12 month
• Approval/implementation: approved by the State Bureau of Technical Supervision on 1997-06-16, implemented on 1997-12-01

2. Scope of application and non-applicability

• Scope of application: This standard specifies methods for calculating vapor pressure, relative density, and motor octane number from the composition of liquefied petroleum gas; it applies to liquefied petroleum gas.
• Not applicable: Not applicable to products whose residue determined in accordance with SY 7509 is greater than 0.05 mL/100 mL. The motor octane number applies only to mixture samples with a propylene content not greater than 20%.
• Safety note: Liquefied petroleum gas is volatile and extremely flammable; relevant safety issues should be noted during operation.

3. Method principle

Determine the composition of liquefied petroleum gas in accordance with SH/T 0230. From the liquid volume percentage of each component, the vapor pressure, relative density, and motor octane number of the sample can be calculated. For conversion among sample composition analyses expressed as gas volume (mole), mass, or liquid volume, Appendix A (ASTM D2421) can be used.

4. Reagents and materials (purity / preparation)

not provided in the available source.

5. Instruments and equipment

not provided in the available source (for instruments required for composition determination, see the referenced standard SH/T 0230).

6. Recommended operating conditions

not provided in the available source.

7. Sampling and sample preparation

not provided in the available source.

8. Analytical procedure

• Determine the composition of liquefied petroleum gas in accordance with SH/T 0230.
• Vapor pressure calculation: The vapor pressure of the sample at 37.8 ℃ is calculated according to formula (1), and the result is rounded to an integer.
• Relative density calculation: The relative density of the sample at 15.6 ℃ is calculated according to formula (2), and the result is rounded to three decimal places.
• Density calculation: a) The density of the sample at 15.6 ℃ is calculated according to formula (3), and the result is rounded to three decimal places; b) The density of the sample at 15.0 ℃ is converted according to SH/T 0221 Appendix B Table B1, converting the density of the sample at 15.6 ℃ to the density at 15.0 ℃ for reporting, and the result is rounded to three decimal places.
• Motor octane number calculation: The motor octane number (MON) of the sample is calculated according to formula (4); the result for a single component is taken to 0.1 MON, and the final result is taken to 0.5 MON.

9. Qualitative and quantitative determination and calculation formulas

• Vapor pressure (37.8 ℃), formula (1): the result is rounded to an integer. Where: pᵢ is the vapor pressure of a certain component at 37.8 ℃ (see Table 1), kPa; c is the liquid volume percentage of a certain component in the sample, % (V/V). (source-text extraction shows the formula body as "-2P:9100", suspected to be in the form Σpᵢc/100, requires confirmation against the source standard (source-text extraction))
• Relative density (15.6 ℃), formula (2): the result is rounded to three decimal places. Where: dᵢ is the relative density of a certain component at 15.6 ℃ (see Table 1); c is the liquid volume percentage of a certain component in the sample, % (V/V). (source-text extraction shows the formula body as "≥4:9/00", suspected to be in the form Σdᵢc/100, requires confirmation against the source standard (source-text extraction))
• Density (15.6 ℃), formula (3): the result is rounded to three decimal places. Where: the relative density of the sample at 15.6 ℃; P is the density of water at 15.6 ℃ (0.999 0 g/cm³). (source-text extraction shows the formula body as "31=3•P", requires confirmation against the source standard (source-text extraction))
• Density (15.0 ℃): converted according to SH/T 0221 Appendix B Table B1 from the density at 15.6 ℃, and the result is rounded to three decimal places.
• Motor octane number, formula (4): the result for a single component is taken to 0.1 MON, and the final result is taken to 0.5 MON. Where: Mᵢ is the motor octane number of a certain component (see Table 1), MON; c is the liquid volume percentage of a certain component in the sample, % (V/V). (source-text extraction shows the formula body as "x-M-9/100", suspected to be in the form ΣMᵢc/100, requires confirmation against the source standard (source-text extraction))

Table 1 Data used to calculate physical properties of liquefied petroleum gas (vapor pressure 37.8 ℃, kPa; relative density 15.6/15.6 ℃; motor octane number blending value, MON):

Note 1): The vapor pressure and motor octane number blending values are empirical values and are applicable only to the calculation process described in this standard. Note 2): The vapor pressure, relative density, and motor octane number blending value data are selected from the 1992 edition of the American Petroleum Institute (API) Technical Data Book—Petroleum Refining, Volume 1~6 chapters.

10. Precision

not provided in the available source (only the significant figures/rounding requirements for each calculation result are specified, see Section 9).

11. Report

not provided in the available source (only rounding requirements such as each calculation result being rounded to an integer or three decimal places, and MON being taken to 0.5, are specified).

12. Referenced documents

• SH/T 0221 Determination of density or relative density of liquefied petroleum gas (pressure densimeter method)
• SH/T 0230 Determination of composition of liquefied petroleum gas (chromatographic method)
• SY 7509 Determination of residue of liquefied petroleum gas
• ASTM D2421 C₅ and conversion method among gas volume, liquid volume, and mass in light hydrocarbons
• Appendix A (normative appendix): C₅ and conversion method among gas volume, liquid volume, and mass in light hydrocarbons (ASTM D2421-95 Chapter 4 and Appendix X)

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