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GB/T 21446-2025: Measurement of natural gas flow by means of standardized orifice meter
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Std ID	Version	USD	Buy	Deliver [PDF] in	Title (Description)
GB/T 21446-2025	English	1959	Add to Cart	11 days [Need to translate]	Measurement of natural gas flow by means of standardized orifice meter
GB/T 21446-2008	English	RFQ	ASK	3 days [Need to translate]	Measurement of natural gas flow by means of standard orifice meter

GB/T 21446-2025: Measurement of natural gas flow by means of standardized orifice meter

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ICS 75.180.30 CCSE98 National Standards of the People's Republic of China Replaces GB/T 21446-2008 Measure natural gas flow using a standard orifice plate flow meter Published on 2025-10-05 Implemented on May 1, 2026 State Administration for Market Regulation The State Administration for Standardization issued a statement.

Table of contents

Preface V 1.Scope 1 2 Normative References 1 3.Terms, Definitions, and Symbols 1 3.1 Terms and Definitions 1 3.2 Symbol 4 4.Principles and Composition 5. 4.1 Principle 5 4.2 Basic Components 5 5.General Requirements for Measurement 5.1 Throttling device 5 5.2 Gas Flow Conditions 6

6 Installation Requirements

6.1 General Requirements 6 6.2 Straight Pipe Section Conditions 6 6.3 Straight pipe section length and layout requirements 7 6.4 Flow regulator 11 6.5 Installation of the orifice plate holder 15 6.6 Assembly and gaskets 16 6.7 Parameter Measurement and Signal Leads 17 7.Technical Requirements for Orifice Plates and Orifice Plate Holders 17 7.1 Orifice Plate 17 7.2 Orifice Plate Holder 20 8.Inspection Requirements 23 8.1 Geometric inspection of the throttling device 23 8.2 Coefficient Verification and Actual Flow Calibration 24 9.Flow Calculation Methods 24 9.1 General Rule 24 9.2 Applicable Conditions 24 9.3 Natural Gas Flow Calculation Method 25 9.4 Parameter Determination 26 9.5 Value Selection Methods and Data Rounding 28 9.6 Orifice Plate Flowmeter Metering System 28 10 Uncertainty 29 10.1 Uncertainty Assessment 29 10.2 Uncertainty Calculation 29 Appendix A (Normative) Determination of Relevant Parameters for Flow Calculation 34 A.1 Pipeline Reynolds Number ReD 34 A.2 Calculation of physical property parameters under standard reference conditions 36 A.3 Calculation of physical property parameters under operating conditions 36 A.4 Calculation of Overcompression Coefficient 36 A.5 Determination of the isentropic index κ of natural gas 37 A.6 Commonly Used Tables for Natural Gas Flow Calculation 38 Appendix B (Normative) Parameter Measurement and Signal Piping 42 B.1 Requirements for the selection of measuring instruments 42 B.2 Installation Requirements for Temperature Measuring Instruments 42 B.3 Pressure and Differential Pressure Measurement Requirements 42 B.4 Requirements for setting up pressure taps 43 B.5 Requirements for pressure-conducting pipe installation 43 B.6 Installation of Differential Pressure Signal Line 44 Appendix C (Informative) Performance Testing of Flow Regulators 47 C.1 Explanation 47 C.2 Evaluation and Testing Requirements for Standard Devices 47 C.3 Performance Testing and Evaluation of Flow Regulators 47 Appendix D (Informative) Handling of throttling devices that deviate from standard specifications during use 50 D.1 Explanation 50 D.2 Treatment of abrasion on the sharp edge of the right-angle inlet of the orifice plate 50 D.3 Treatment of abrasion on the inner wall roughness of the measuring tube 51 Appendix E (Informative) Example 52 of Actual Flow Calibration for Standard Throttling Devices E.1 Overview 52 E.2 Calibration Conditions 52 E.3 Calibration Items and Methods for Differential Pressure Devices Using the Discharge Coefficient Method 52 E.4 Uncertainty Estimation of Actual Flow Calibration 53 E.5 Calibration Result Example 54 Appendix F (Informative) Examples of Natural Gas Flow Calculation and Design Calculation 56 F.1 Example 56 of Natural Gas Flow Calculation F.2 Example 67 of Orifice Plate Opening Diameter Design Calculation F.3 Differential Pressure Range Design Calculation Example 71 F.4 Uncertainty Estimation 73 Appendix G (Informative) Flowchart of Natural Gas Flow Calculation and Design Calculation Procedure 76 G.1 Explanation 76 G.2 Iterative Calculation Format 76 G.3 Computer Calculation Program Flowchart 78 Appendix H (Informative) Natural Gas Flow Calculator 81 H.1 Overview 81 H.2 Principles and Composition 81 H.3 Appearance 81 H.4 Metrological Performance 81 H.5 Functional Requirements 83 H.6 Traffic Algorithm (Mathematical Model) 84 H.7 Traffic Computer Hardware and Software Technical Requirements 84 References 88 Figure 1.Schematic diagram of the composition and installation of an orifice plate flow meter. Figure 2.Layout plan of a full-bore valve with β=0.6 fully open. Figure 3 Installation Example 10 Figure 4 19 Tube Bundle Flow Adjuster 12 Figure 5 Example 14 of installing a 19-tube bundle flow adjuster downstream of a single elbow. Figure 6 Zanker Rectifier Board 15 Figure 7 Schematic diagram of the deviation between the orifice plate and the measuring tube axis 16 Figure 8 Standard orifice plate 18 Figure 9.Orifice plate straightness measurement 19 Figure 10 Flange pressure tapping orifice plate holder 21 Figure 11 Angle-connected pressure-taking plate holder 22 Figure B.1 Schematic diagram of pressure tap location 43 Figure B.2 Differential pressure gauge installed above the throttling device (no corrosive media) 44 Figure B.3 Differential pressure gauge installed below the throttling device (no corrosive media) 45 Figure B.4 Differential pressure gauge installed above the throttling device (including corrosive media) 45 Figure B.5 Differential pressure gauge installed below the throttling device (including corrosive media) 46 Figure C.1 Chevron hydrocyclone 48 Figure G.1 Flowchart of Flow Calculation Program 78 Figure G.2 Flowchart of the orifice plate opening diameter calculation procedure 79 Figure G.3 Flowchart of Differential Pressure Range Calculation Program 80 Table 1.Permissible straight pipe section length between orifice plate and flow obstruction (without flow conditioner, values are expressed as multiples of pipe inner diameter D) 9 Table 2.Permissible straight pipe section length between the orifice plate and the 19-tube bundle flow conditioner (the distance between the flow throttling element and the orifice plate is LZ, and the value is expressed as follows). (Multiples of pipe inner diameter D) 13 Table 3.Limits for orifice diameter, measuring tube inner diameter, diameter ratio, and pipe Reynolds number (Table 24) Table 4.Maximum value of 104Ra/D. 24 Table 5.Minimum value of 104Ra/D. 25 Table 6.Minimum number of significant digits for coefficient parameters (Table 28) Table 7.Tolerances and Tolerance Factors for Platinum Resistance Therapy (PTT) 32 Table A.1 Linear Expansion Coefficient Values of Metallic Materials (20℃~100℃) (Table 38) Table A.2 Dynamic viscosity μ of methane at different pressures and temperatures. (Table 38) Table A.3 Physical property parameters of commonly used components of natural gas (Table 39) Table A.4 Methane cp and cv values at different pressures and temperatures. Table A.5 Equivalent Absolute Roughness K Values of Steel Pipe Inner Wall (Table 40) Table B.1 Pressure-conducting tube length and inner diameter (Table 43) Table D.1 Relationship between bK and rK/d 50 Table D.2 Standard orifice plate γo values (Table 51) Table E.1 Calculation of Uncertainty Components of Measurement Results for Standard Gas Flow Standard Device Verification or Calibration Standard Throttling Device (Table 54) Table E.2 Calibration Results of Differential Pressure Device Discharge Coefficient Method 54 Table F.1 Composition of Natural Gas 56 Table F.2 Calculation of Natural Gas Compressibility Factor and Overcompressibility Factor 58 Table F.3 Calculation of Natural Gas Density and Relative Density 60 Table F.4 Calorific Value Calculation Table 62 Table F.5 Calculation of Natural Gas Isotropic Index (Table 63) Table F.6 Calculation of Natural Gas Dynamic Viscosity 65 Table F.7 Natural Gas Flow Calculation Order and Significant Digit Values Table 65 Table G.1 Format for Flow Iteration Calculation and Energy Calculation 76 Table G.2 Iterative Calculation Format for Orifice Plate Opening Diameter 77 Table G.3 Differential Pressure Range Iterative Calculation Format 77 Table H.1 Maximum Permissible Error of Flow Metering System and Accuracy Class of Flow Computer 81 Table H.2 Accuracy Classes and Maximum Permissible Errors of Flow Calculators 82 Table H.3 Maximum Permissible Error of Flow Calculator Functional Units and Measurement Channels 82

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1.Structure and Drafting Rules of Standardization Documents". Drafting. This document replaces GB/T 21446-2008 "Measurement of Natural Gas Flow Rate Using Standard Orifice Plate Flow Meters" and is consistent with GB/T 21446-2008. Compared to previous versions, aside from structural adjustments and editorial changes, the main technical changes are as follows. a) Added a definition for a natural gas flow totalizer and changed the definition for a standard orifice plate flowmeter (see Chapter 3,.2008 edition). Chapter 3); b) A new chapter, "Principles and Composition," has been added (see Chapter 4, sections 5.1 and 8.1 of the.2008 edition); c) The standard reference conditions have been changed (see 9.1, 4.3 of the.2008 edition); d) Added the provision that "the straight pipe section adjacent to the orifice plate, 10D upstream or after the flow conditioner and 4D downstream, is permitted to be ground." Channel processing shall be performed in a manner described in section 6.1.1, section 5.1.2 of the.2008 edition. e) The perpendicularity deviation of the pressure tapping hole axis has been increased to no more than 3° (see 7.2.2.3, 6.2.1.3 in the.2008 version); f) Added "Outside of 10D, if the upstream diameter of the step is greater than the downstream diameter of the step, the allowable diameter difference or step size can be increased by 2%". When the diameter is increased to 6%, the diameter of the pipes on both sides of the step should be between 0.98D and 1.06D (see 6.2.2.6, 5.2.2.6 in the.2008 edition); g) The distance requirement between two 45° bends on the same plane has been changed (see Table 1 in 6.3.7, 5.3.7 in the.2008 version). Table 2); h) Added requirements for the use of correction factors after coefficient verification and online calibration (see 8.2, 7.2 of the.2008 edition); i) Change "Scope of application for measurement" to "Applicable conditions" (see 9.2, 8.2 in the.2008 edition); j) The definition of uncertainty has been removed (see Chapter 10, 9.1 of the.2008 edition); k) The formula for calculating the uncertainty of mass flow rate measurement has been changed (see 10.2.2, 9.2.2 in the.2008 version); l) GB/T 30491 (see Appendix A, Appendix A of the.2008 edition) has been added as the basis for calculating physical property parameters; m) The table of pressure-conducting tube lengths and inner diameters has been revised (see Table B.1, Table C.1 in the.2008 edition); n) The phrase "determination of pipe inner wall roughness by fluid experiments" has been removed (see D.4 in the.2008 edition); o) Change "Online calibration of natural gas orifice plate flowmeter metering system" to "Example of actual flow calibration of standard throttling device" (see Appendix E (Appendix E of the.2008 edition); p) The calculations for isentropic exponent, dynamic viscosity, uncertainty, etc., have been modified (see Appendix F,.2008 edition). Additional changes have been made to the standard parameters. Estimation of energy measurement uncertainty under specific conditions (see Appendix F.4.3); q) Change "Basic Technical Requirements for Natural Gas Flow Computer System" to "Natural Gas Flow Computer" (see Appendix H,.2008 edition). Appendix H). Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents. This document was proposed and is under the jurisdiction of the National Technical Committee on Standardization of Petroleum and Natural Gas (SAC/TC355). This document was drafted by. Southwest Branch of China Petroleum Engineering & Construction Corporation and Southwest Oil & Gas Company of China National Petroleum Corporation. Daqing Oilfield Branch Company, China Oilfield Pipeline Network Corporation West-East Gas Pipeline Branch Company, Daqing Oilfield Design Institute Co., Ltd., Beijing Bosida New Century Measurement & Control Technology Co., Ltd., Chengdu Hangli Valve Complete Equipment Co., Ltd., and Beijing Gas Group Co., Ltd. The main drafters of this document are. Xu Gang, Du Tonglin, Li Wanjun, Song Chaofan, Luo Mingqiang, Huang Min, Huang He, Xiao Di, Pu Liming, Ren Jia, and Guan Yue. Wu Yan, Wang Hailan, He Min, Zhang Zhili, Zan Linfeng, Xiao Yuegen, Fang Fusheng, Huang Yangting, Chen Zhi, Zhou Haiyan, Zhang Han. This document was first published in.2008, and this is its first revision. Measure natural gas flow using a standard orifice plate flow meter

1 Scope

This document specifies the technical requirements for the processing and installation of standard orifice plates, and provides the mass flow rate of natural gas and the volumetric flow rate under standard reference conditions. Methods for calculating energy flow and the assessment of measurement uncertainty. This document applies to throttling devices for single-phase natural gas, with pressure tapping methods including flange and corner connections, and orifice plate opening diameter equal to or greater than [missing information]. 12.5mm, measuring tube inner diameter equal to or greater than 50mm and equal to or less than 1000mm, diameter ratio equal to or greater than 0.1 and equal to or less than 0.1 For cases where the pipeline Reynolds number is 0.75 or greater than 5000.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included. For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document. GB/T 8170 Rules for rounding off numerical values and the representation and determination of limiting values GB/T 11062 Calculation Methods for Calorific Value, Density, Relative Density and Wobbe Index of Natural Gas GB/T 13610 Compositional Analysis of Natural Gas - Gas Chromatography GB/T 15464 General Technical Requirements for Packaging of Instruments and Meters GB/T 17747 (all parts) Calculation of natural gas compressibility factor GB/T 18603 Technical Requirements for Natural Gas Metering Systems GB/T 30491 (all parts) Calculation of thermodynamic properties of natural gas GB/T 35186 Performance Evaluation of Natural Gas Metering Systems JJG640 Differential Pressure Flow Meter Verification Procedure 3.Terms, Definitions and Symbols 3.1 Terms and Definitions The following terms and definitions apply to this document. 3.1.1 A thin plate with circular perforations, obtained through machining. Its throttling orifice has a cylindrical surface perpendicular to the upstream end face of the orifice plate, and its edges are... The orifice plate is sharp, and its thickness is relatively small compared to its diameter. It should be designed within the scope and requirements specified in this document. Manufacturing, installation and use. Note. Hereinafter referred to as "perforated plate". 3.1.2 orificeplateholder A pressurized piping assembly used to output the static pressure difference generated by the orifice plate and to house and position the orifice plate. [Source. GB/T 8423.4-2022, 4.1.65] ...