SL/T 426-2021 in English

VALID

Basic technical conditions for water measurement equipment

Issued on:2021-10-26
Implemented on:2022-01-26
File Format:PDF
Delivery:Via email within 2~4 business days

Price(USD)： $469.00
$455.00

Standard No:	SL/T 426-2021
Document status:	VALID
Title in English:	Basic technical conditions for water measurement equipment
Title in Chinese:	水量计量设备基本技术条件
Language:	English
File Format:	Electronic (PDF)
Delivery:	Via email within 2~4 business days
Issued on:	2021-10-26
Implemented on:	2022-01-26
ICS Classification:	07.060-Geology. Meteorology. Hydrology
Chinese Classification:	N93-Hydrology and water conservancy instrument
Professional Classification:	SL-Water Resources
Related Keywords:	water measurement equipment introduction background water metering equipment water quantity measurement reclassify key equipment equipment type measurement range maximum water bodies

Introduction

Background of standard revision and core changes

SL/T 426-2021, as an important technical standard in the water conservancy industry, replaces the 2008 edition of the specification and focuses on the technical requirements for water metering equipment. The main changes in this revision include:

Cancel the water quality monitoring content and focus on the technical indicators of water quantity measurement
Reclassify the technical requirements according to the measurement method (open channel/pipeline)
Add new equipment specifications such as Acoustic Doppler Flow Profiler
Refine the measurement performance error requirements and test methods

Comparison of technical requirements for key equipment

Equipment type	Measurement range	Maximum allowable error	Applicable scenarios
Rotor flowmeter	0.015-15m/s	±0.65%-1.5%	Rate ratio measurement, low sand content section
Acoustic time difference flowmeter	DN50-2000mm	±1.0%	Clean water pipeline, large diameter measurement
Electronic flowmeter	DN15-2000mm	±0.5%-2.5%	Full pipe pressurized pipeline
Electronic remote water meter	DN15-500mm	±2%-5%	Small water intake project

Implementation points and case analysis

Typical scheme for open channel metering

A certain irrigation district adopts a combination of Parshall flume + radar water level meter:

A straight section of 5 times the channel width is set according to standard requirements
IP67 protection grade water level meter is installed, with a measurement error of ±1cm
Flow rate is calculated using the SL 537 formula and calibrated once a year

Common problems in pipeline metering

Improper installation of electromagnetic flowmeter at a pump station leads to excessive errors:

Wrong practice: The rear straight pipe section is only 2 times the pipe diameter
Standard requirements: The front straight pipe section is 10D and the rear straight pipe section is 5D (D is the pipe diameter)
Corrective measures: After installing a flow conditioner, the error is reduced from 5% to 1.2%

Equipment selection decision tree

Open channel measurement:Stable water flow→SelectWeir flume method; High sand content→ADCP; Surface velocity→Electromagnetic current meter

Pipeline measurement:Full pipe→Electromagnetic/ultrasonic flowmeter; Partial pipe→Refer to the open channel solution

Suggestions for the implementation of the standard

Establish a periodic verification system: key equipment should be verified once a year, and the period for water bodies with high sand content should be shortened to half a year
Give priority to digital interface equipment (RS485/MODBUS) to improve data transmission reliability
Special environments must meet IP68 protection and lightning protection requirements (GB/T 17626.5)