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GB/T 21391-2008 (GB/T21391-2008)

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GB/T 21391-2008: PDF in English (GBT 21391-2008)
GB/T 21391-2008
GB
NATIONAL STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 75.180.30
E 98
Measurement of natural gas flow by turbine meters
ISSUED ON. FEBRUARY 02, 2008
IMPLEMENTED ON. AUGUST 01, 2008
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of the PRC.
Table of contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms, definitions and symbols ... 6 
4 Measurement principle ... 9 
5 Metering performance ... 10 
6 Flow meter requirements ... 11 
7 Installation requirements, use and maintenance ... 17 
8 Flow calculation method and measurement uncertainty estimation ... 23 
Appendix A (Normative) Real-flow calibration ... 29 
Appendix B (Informative) Other performance characteristics of flow meter ... 41 
Appendix C (Informative) Field test of flow meter ... 46 
Appendix D (Informative) Example of natural gas flow calculation ... 48 
Foreword
This standard is non-equivalent to the European standard EN 12261.2002 “Gas
flow meter - gas turbine flow meter”, makes reference to AGA No.7.2004
“Measurement of fuel gas by turbine meters”, ISO 9951.1993 “Measurement of
gas flow in closed conduits - Turbine meters”, and JJG 198-1994 “Verification
regulation of velocity flow meter”, AND is, combining with the actual
requirements for local use, added with the standard reference conditions for the
calculation of natural gas volume and calorific value, the explosion proof
requirements for using turbine meter to measure the natural gas flow, the
requirements for integrated intelligent flow meter, the calculation for using
turbine meter to measure the natural gas flow, the calculation of compression
factor, the estimation of uncertainty, real-flow calibration, and the application
after calibration, and the other technical provisions.
The main differences between this standard and EN 12261.2002 are as follows.
- ADD Chapter 4 “Measurement principles”, Chapter 6 “Flow meter
requirements”, Chapter 7 “Installation requirements, use and maintenance”,
and Chapter 8 “Flow calculation methods and measurement uncertainty
estimation”;
- ADD Appendix B “Additional performance characteristics of the flow meter”,
Appendix C “Field test of flow meters”, and Appendix D “Example of natural
gas flow calculation”.
- DELETE Chapter 4 “Flow meter classification” and some contents on type
tests from Chapter 5 and 6 of EN 12261;
- MODIFY some of the statements that apply to international standards into
the statements applicable to Chinese standard.
Appendix A to this standard is a normative appendix.Appendix B, Appendix C
and Appendix D are informative.
This standard was proposed by China National Petroleum Corporation.
This standard shall be under the jurisdiction of the Oil & Gas Measurement and
Analysis Method Professional Standardization Technical Committee.
The responsible drafting organizations of this standard. National Crude Oil Flow
Measurement Station Chengdu Natural Gas Flow Substation.
The participating drafting organizations of this standard. China Petroleum
Southwest Oil and Gas Field Branch.
Measurement of natural gas flow by turbine meters
1 Scope
This standard specifies the measurement conditions, requirements,
performance, installation, real-flow calibration and field inspection of gas turbine
flow meter (hereinafter referred to as flow meter) for natural gas flow
measurement.
The natural gas component measured by the flow meter shall be within the
range specified in GB 17820-1999, GB/T 17747.1-1999, GB/T 17747.2-1999
and GB/T 17747.3-1999, AND the true relative density of natural gas is 0.55 ~
0.80.
This standard specifies that the standard reference conditions for the
measurement of natural gas flow and the combustion standard reference
conditions for the calorific value measurement are absolute pressure Pn =
0.101325 MPa and the thermodynamic temperature Tn = 293.15 K. It may also
use the contracted pressure and temperature as the reference conditions.
Unless otherwise stated, the pressure referred to in this standard is gauge
pressure.
2 Normative references
The provisions in following documents become the provisions of this Standard
through reference in this Standard. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this Standard;
however, parties who reach an agreement based on this Standard are
encouraged to study if the latest versions of these documents are applicable.
For undated references, the latest edition of the referenced document applies.
GB 3836.1-2000 Explosive atmospheres - Part 1. Equipment - General
requirements (eqv IEC 60079-0.1998)
GB 3836.2-2000 Electrical apparatus for explosive gas atmospheres - Part
2. Flameproof enclosure d (eqv IEC 60079-1.1990)
GB 3836.4-2000 Electrical apparatus for explosive gas atmospheres - Part
4. Intrinsic safety i (eqv IEC 60079-11.1999)
GB/T 4208 Degree of protection of enclosure (IP code)
GB/T 11062-1998 Natural gas - Calculation of calorific values, density,
relative density and Wobbe index from composition (neq ISO 6976.1995)
GB/T 13610-2003 Analysis of natural gas by gas chromatography
GB/T 15464 General purpose specification for the packaging of
instrumentation products
GB/T 17747.1-1999 Natural gas - Calculation of compression factor - Part 1.
Introduction and guideline (eqv ISO 12213-1.1997)
GB/T 17747.2-1999 Natural gas - Calculation of compression factor - Part 2.
Calculation using molar (eqv ISO 12213-2.1997)
GB/T 17747.3-1999 Natural gas - Calculation of compression factor - Part 3.
Calculation using physical properties (eqv ISO 12213-3.1997)
GB 17820-1999 Natural gas
GB/T 18603-2001 Technical requirements for measuring systems for natural
gas
GB/T 18940-2003 Measurement of gas flow in closed conduits - Turbine
meters (ISO 9951.1993, IDT)
JJG 198 Verification regulation of velocity flow meter
SY/T 6143-2004 Measurement of natural gas flow with standard orifice flow
meter
3 Terms, definitions and symbols
The following terms and definitions apply to this standard.
3.1
Turbine gas meter
It refers to the metering equipment for which the rotation speed and gas
volume flow are in functional relationship when the impeller rotates under the
effect of gas flow. The gas volume flow passing through the flow meter is
obtained based on the number of impeller rotations.
3.2
Rangeability
5.2.2 Error requirements for integrated intelligent flow meter
As for the integrated intelligent flow meter, within its designated flow range, its
error shall not be more than ± 1.5%.
5.3 Repeatability
The repeatability of the flow rate of each flow meter at each flow point under
operating condition shall not exceed 1/3 of the maximum allowable error of the
flow meter. The repeatability of an integrated intelligent flow meter shall not
exceed 1/2 of the maximum allowable error of the flow meter.
5.4 Calibration
It shall, based on the working pressure as specified by the user, calibrate the
flow meter under one or more pressures. If the flow meter is calibrated under
the calibration pressure ptest, the suitable pressure range of this flow meter is
0.5 ptest ~ 2.0 ptest. The choice of flow meter ptest is given in Appendix A.
5.5 Short-term overload
The flow meter shall be capable of operating at a flow rate of 1.2 qmax for 30
minutes without damage, AND its performance is not affected.
5.6 Working temperature range
The temperature range of the gas flow that complies with the performance
requirements of the flow meter shall be at least -10 °C ~ 40 °C.
5.7 Installation conditions
The influence of the installation conditions on the flow meter shall not exceed
1/3 of the maximum allowable error as specified in Table 2. The test of influence
of the installation conditions on the flow meter is described in Appendix E of
GB/T 18940-2003.
5.8 Maximum allowable pressure loss
The manufacturer shall provide pressure loss data for the flow meter or flow
meter components of various types and caliber. For more details, SEE
Appendix B.
6 Flow meter requirements
6.1 General
Normally on the flow meter shall be provided with at least one pressure taps for
measurement, in order to measure the static pressure at the turbine impeller
under measurement conditions. This pressure tap is marked with “pm”; if there
are more than one “pm” pressure taps, when using the air under normal
pressure (± 10 kPa) is used for test, the difference between the pressure
readings at each pressure tap shall not exceed 50 Pa.
6.4.2 Other pressure taps
The other pressure taps on the flow meter are marked with “p”.
6.4.3 Size
The diameter of the circular pressure tap shall be between 3 mm and 12 mm,
AND its length shall be equal to the aperture. In addition, the others shall comply
with the provisions of SY/T 6143-2004.
The size of the grooved pressure tap in the direction of flow shall be at least 2
mm, the maximum size of 10 mm, cross-se...
......
 
(Above excerpt was released on 2017-03-06, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT21391-2008