GB/T 18604-2023 (English Version)

Standard No.: GB/T 18604-2023
Language: Chinese, English version preview
Release Date: 2023
Published By: General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Latest: GB/T 18604-2023

Introduction

Core changes in the standard revision

Revision dimensions	Contents of the 2014 version	Changes in the 2023 version
Scope of application	Limited to specific places such as gathering and transportation devices	Added application scenarios such as new measurement standard devices
Performance indicators	Does not distinguish between caliber differences	Specifies the different error limits for flow meters ≥300mm and <300mm
Installation requirements	Ra value is not specified	New requirement for inner surface roughness of straight pipe section ≤3.2μm

Analysis of key technologies

Principle of propagation time difference method

The flow velocity is calculated by measuring the time difference ΔT between the upstream and downstream sound pulses of the ultrasonic transducer and combining the formula V=L²ΔT/(2X·tU·tD).

L: length of the sound channel (Appendix A Figure 1)
X: axial projection distance of the sound channel
tU/tD: upstream/downstream propagation time

Implementation points

Installation specifications

Straight pipe section configuration: When there is no flow conditioner, the upstream ≥50D, the downstream ≥5D
Pressure tapping requirements: The reduced-diameter flowmeter must be marked with "Pm", and the pressure difference must be ≤100Pa (7.2.6)
Temperature measurement: Special design is required when the insertion depth is ＞1/3D (8.2.5)

Maintenance strategy

Project	Cycle	Inspection content
Regular inspection	≥1 time/year	Channel status, zero flow reading, transducer deposits
Offset check	After each calibration	Deviation from the last calibration result (8.3.3)

Uncertainty assessment model

Expanded uncertainty of volume flow under standard reference conditions:

Ur(qn)=k×√[ur²(qf)+ur²(Pf)+ur²(Tf)+ur²(Zf)+ur²(Zn)+ur²(an)]（k=2）

An is the additional installation uncertainty, and it is recommended to take 1/3 of the flow meter MPE (10.2.1)

GB/T 18604-2023 history

2023 GB/T 18604-2023 Measuring natural gas flow with a gas ultrasonic flowmeter
2014 GB/T 18604-2014 Measurement of natural gas flow by gas ultrasonic flow meters
2001 GB/T 18604-2001 Measurement of natural gas flow by ultrasonic flow meter