GB/T 18604-2023 PDF English
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| GB/T 18604-2023 | English | 680 |
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Measurement of natural gas flow by gas ultrasonic flow meters
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| GB/T 18604-2014 | English | 285 |
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Measurement of natural gas flow by gas ultrasonic flow meters
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| GB/T 18604-2001 | English | RFQ |
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Measurement of natural gas flow by ultrasonic flow meter
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GB/T 18604-2023: Measurement of natural gas flow by gas ultrasonic flow meters---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT18604-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 75.180.30
CCS E 98
GB/T 18604-2023
Replacing GB/T 18604-2014
Measurement of natural gas flow by gas ultrasonic flow
meters
Issued on. MAY 23, 2023
Implemented on. DECEMBER 01, 2023
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 4
1 Scope... 7
2 Normative references... 7
3 Terms and definitions... 8
4 Measurement principle... 12
5 Working conditions... 13
6 Measurement performance requirements... 14
7 Flow meters... 16
8 Installation and maintenance requirements... 24
9 Field verification test requirements... 29
10 Flow calculation method and estimation of measurement uncertainty... 30
Annex A (informative) Basic principles of measurement by gas ultrasonic flow meters
... 36
Annex B (informative) Real-flow calibration of flow meters... 45
Annex C (normative) Factory-exit test requirements... 52
Annex D (informative) Documents available... 54
Annex E (informative) Generation and prevention measures of acoustic noise... 57
Annex F (informative) Performance verification test of flow meters and flow
conditioners... 63
Annex G (informative) Inspection and assurance of field measurement performance of
flow meters... 65
Bibliography... 69
1 Scope
This document specifies the measurement performance, flow meter body, installation
and maintenance, field verification test requirements, as well as flow calculation
method and measurement uncertainty estimation of insertion-type gas ultrasonic flow
meters using transit-time difference method (hereinafter referred to as “flow meters”).
This document applies to measurement of natural gas flow in gathering and
transmission equipment, gas transmission pipelines, storage facilities, gas distribution
systems, user metering systems, measuring standard devices and other application
places.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 2624.2 Measurement of fluid flow by means of pressure differential devices
inserted in circular cross-section conduits running full - Part 2.Orifice plates
GB/T 3836.1 Explosive atmospheres - Part 1.Equipment - General requirements
GB/T 3836.2 Explosive atmospheres - Part 2.Equipment protection by flameproof
enclosures “d”
GB/T 3836.4 Explosive atmospheres - Part 4.Equipment protection by intrinsic
safety “i”
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
transit-time difference method
A gas flow measurement method by using the transit-time difference of two ultrasonic
signals propagating downstream and upstream to determine the average gas flow along
the acoustic path within the same stroke in the flowing gas.
3.2
ultrasonic transducer
A component that converts acoustic energy into electrical signals and converts electrical
signals into acoustic energy.
3.3
signal processing unit; SPU
An electronic device composed of electronic components and a microprocessor system,
which has the functions of receiving ultrasonic transducer signals, processing
measurement signals, displaying, outputting and recording measurement results.
3.4
meter body
A pipe section through which the measured gas passes, which is equipped with
components such as ultrasonic transducers and pressure measuring joints, and is
specially manufactured to meet the requirements of relevant standards in all aspects.
3.5
acoustic path
Actual path that an ultrasonic signal travels between a pair of transmitting and receiving
ultrasonic transducers.
4 Measurement principle
4.1 Basic principle
A gas ultrasonic flow meter using transit-time difference method is a velocity flow
meter that measures the transit-time of high-frequency sound pulses to obtain the gas
flow. The transit-time is measured by the sound pulses transmitted and received
between paired transducers outside or inside the pipeline. The sound pulse propagates
in the oblique direction (see Figure 1).
4.2 Factors affecting measurement accuracy
4.2.1 The internal factors affecting measurement accuracy are mainly.
4.2.2 The internal factors affecting measurement accuracy are mainly.
5 Working conditions
5.1 Natural gas quality
The natural gas composition measured by the flow meter shall be within the range
specified in GB/T 17747 (all parts), and the relative density of natural gas is 0.55 ~ 0.80.
5.2 Pressure
The minimum working pressure of ultrasonic transducers shall ensure that the sound
pulse can propagate normally in natural gas.
5.3 Temperature
The manufacturer shall provide flow meters that meet the temperature range
requirements according to the actual working conditions of the user, including specified
working and ambient temperature range of flow meter body, field-installed electronic
devices, and its related external equipment, cable connections and ultrasonic
transducers.
5.4 Flow range and flow direction
The flow measurement range of flow meters is determined by the actual flow velocity
of the gas. The typical flow velocity range of the measured natural gas should be (0.3 ~
30) m/s.
5.5 Velocity distribution
Under ideal conditions, the natural gas flow entering the flow meter shall be a
symmetrical and fully developed turbulent velocity distribution.
6 Measurement performance requirements
6.1 General requirements
This Clause specifies a set of minimum measurement performance requirements that
flow meters shall meet. Before adjusting the real flow calibration coefficient, the flow
meter shall meet these performance requirements to ensure that the flow meter’s own
problems and defects are not covered up by the calibration coefficient adjustment.
6.2 Measurement performance requirements for multi-acoustic-path gas
ultrasonic flow meters
6.2.1 General
Before adjusting the calibration coefficient, the general measurement performance of
all multi-acoustic-path gas ultrasonic flow meters shall meet the following requirements.
6.2.2 Accuracy of large-diameter flow meters
Before adjusting the calibration coefficient, multi-acoustic-path gas ultrasonic flow
meters with a diameter equal to or greater than 300 mm shall meet the measurement
accuracy requirements shown in Figure 2 and the following.
6.2.3 Accuracy of small-diameter flow meters
Before adjusting the calibration coefficient, multi-acoustic-path gas ultrasonic flow
meters with a diameter less than 300 mm shall meet the measurement accuracy
requirements shown in Figure 2 and the following.
6.3 Measurement performance requirements for single-acoustic-path gas
ultrasonic flow meters
6.4 Effect of working conditions on measurement performance
Under the working conditions specified in Clause 5, the flow meter shall meet the
measurement performance requirements specified in 6.1 and 6.2 without any manual
adjustment.
7 Flow meters
7.1 Composition and basic regulations
7.1.1 Composition
A flow meter mainly consists of the following two parts.
7.2 Meter body
7.2.1 Maximum working pressure
The maximum design working pressure of a flow meter shall be the minimum value of
the maximum working pressure of the flow meter body, flange, ultrasonic transducer
components and their mounting parts.
7.2.8 Appearance quality requirements
The appearance quality shall meet the following requirements.
7.2.9 Other requirements
The flow meter shall not roll when placed on a smooth surface with a slope of 10 % to
prevent damage to the protruding ultrasonic transducer and signal processing unit when
it is temporarily placed on the ground during installation or maintenance.
7.3 Ultrasonic transducer
7.3.1 Technical requirements
The manufacturer shall provide the general technical indicators of ultrasonic
transducers, such as. key dimensions, maximum allowable working pressure, working
pressure range, working temperature range, gas composition limit, transducer working
frequency, etc.
7.5 Flow computer
7.5.1 Hardware
The computer code used for flow meter control and operation shall be stored in non-
volatile memory, and all flow calculation constants and manually entered parameters
shall also be stored in non-volatile memory.
7.5.2 Configuration and maintenance software
Flow meters shall have software for local and remote configuration of signal processing
units and monitoring of flow meter operation, as well as alarm and fault indication. The
software shall at least display and record the following data.
7.5.3 Inspection and verification functions
For inspection and verification purposes, all flow calculation constants and parameters
shall be checked and confirmed on the flow computer when the flow meter is operating.
The inspection or verification personnel can view and print the flow measurement
configuration parameters of the signal processing unit.
7.5.4 Alarms
The flow meter shall provide the following alarm status outputs in the form of fail-safe
relay contacts or passive contacts isolated from ground.
8 Installation and maintenance requirements
8.1 Installation influencing factors
8.1.1 Temperature
The ambient temperature for the installation of flow meters shall comply with the
provisions of 5.3.At the same time, according to the specific environment and working
conditions of the installation point, it shall take necessary insulation, antifreeze and
other protective measures (such as rain protection, sun protection, etc.) for the metering
package.
8.3 Maintenance
8.3.1 Daily maintenance
The manufacturer shall be responsible for training the on-site staff on basic operation
and maintenance skills. Daily maintenance mainly involves targeted inspection and
maintenance based on the information fed back by the ultrasonic flow meter’s self-
diagnosis system to ensure the on-site measurement performance of the flow meter. For
relevant technical requirements, see Annex G.
8.3.2 Regular inspection
The inspection frequency shall be determined according to the manufacturer’s
recommended cycle or at least once a year. The inspection content includes whether the
signal processing unit and timing system are working properly, whether the acoustic
path has any faults, whether the zero-flow measurement is accurate, whether there is
any sediment on the surface of the ultrasonic transducer, and whether the signal gain
has a significant change.
8.3.3 Offset inspection
Inspect the offset between the current verification or calibration result and the last
verification or calibration result.
9 Field verification test requirements
9.1 General
The manufacturer shall provide the user with written documents of the field verification
test of flow meters. When it is necessary to conduct a field verification test on the gas
ultrasonic flow meter, it shall be carried out in accordance with 9.2.
9.2 Test content and steps
9.2.1 Appearance inspection
During the appearance inspection, inspect whether the flow meter cavity and ultrasonic
transducer have dirt deposition, wear or other damage that may affect the performance
of the flow meter.
9.3 Test report
The test report shall at least include the following contents. flow meter name, model
specifications, manufacturer, date of start of operation, on-site conditions (gas quality,
flow, pressure, temperature and installation method, etc.), test organization and
personnel, test content and method, test results, abnormal situation cause analysis and
recommended measures.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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