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GB/T 21938-2021: Earth-moving machinery - Hydraulic excavator and backhoe loader lowering control device - Requirements and tests
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GB/T 21938-2021	English	284	Add to Cart	3 days [Need to translate]	Earth-moving machinery - Hydraulic excavator and backhoe loader lowering control device - Requirements and tests
GB/T 21938-2008	English	314	Add to Cart	3 days [Need to translate]	Earth-moving machinery -- Hydraulic excavator and backhoe loader boom-lowering control device -- Requirements and tests

GB/T 21938-2021: Earth-moving machinery - Hydraulic excavator and backhoe loader lowering control device - Requirements and tests

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Earth-moving machinery─Hydraulic excavator and backhoe loader lowering control device─Requirements and tests ICS 53:100 CCSP97 National Standards of People's Republic of China Replacing GB/T 21938-2008 Earthmoving Machinery Hydraulic Excavators and Backhoe Loaders Descent control device requirements and tests (ISO 8643:2017, IDT) Published on 2021-12-31 2022-07-01 Implementation State Administration for Market Regulation Released by the National Standardization Administration directory Preface III Introduction IV 1 Scope 1 2 Normative references 1 3 Terms and Definitions 1 4 Descent control device requirements 2 5 Test method 3 Reference 9

foreword

This document is in accordance with the provisions of GB/T 1:1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules of Standardization Documents" drafted: This document replaces GB/T 21938-2008 "Earth-moving machinery hydraulic excavator and backhoe loader boom lowering control device requirements Compared with GB/T 21938-2008, in addition to structural adjustment and editorial changes, the main technical changes are as follows: a) Changed the scope of the standard (see Chapter 1, Chapter 1 of the:2008 edition); b) Added normative references (see Chapter 2, Chapter 2 of the:2008 edition); c) Some terms and definitions have been changed, added and deleted (see Chapter 3, Chapter 3 of the:2008 edition); d) Changed the requirements for the descent control device (see Chapter 4, Chapter 4 of the:2008 edition); e) Changed the test method (see Chapter 5, Chapter 5 of the:2008 edition); f) Added references (see References): This document is identical to ISO 8643:2017 "Requirements for lowering controls for earth-moving machinery hydraulic excavators and backhoe loaders and test": Please note that some content of this document may be patented: The issuing agency of this document assumes no responsibility for identifying patents: This document is proposed by China Machinery Industry Federation: This document is under the jurisdiction of the National Earthmoving Machinery Standardization Technical Committee (SAC/TC334): This document was drafted by: Jiangsu Xugong Construction Machinery Research Institute Co:, Ltd:, Fujian Jingong Machinery Co:, Ltd:, Tianjin Construction Machinery Research Institute Institute Co:, Ltd:, Xiamen Yulong Machinery Co:, Ltd:, Liuzhou Liugong Excavator Co:, Ltd:, Xinxing Jihua Group Co:, Ltd: The main drafters of this document: Wang Lili, Xiao Chuanqi, Wu Hongli, Chen Xinmin, Liu Xiaoqiang, Duan Huiwen: This document was first published in:2008 and this is the first revision:

Introduction

When an excavator or backhoe loader is used to lift objects, the failure or rupture of the hydraulic line can cause safety problems for people under the raised load: threat: This hazard can be reduced by the use of a descent control device, which ensures that in the event of a hydraulic line failure or rupture, the load is lowered: The drop speed is controlled: The test method is developed based on the hydraulic system design characteristics and operating conditions of hydraulic excavators and backhoes of backhoes: Earthmoving Machinery Hydraulic Excavators and Backhoe Loaders Descent control device requirements and tests

1 Scope

This document specifies the performance requirements and test methods for lowering control devices installed in the moving parts of hydraulic excavators and backhoe loaders: On the hydraulic cylinder of the boom, the intermediate boom and the stick, it is used to control the lowering speed of the boom when the hydraulic pipeline fails or breaks: This document applies to hydraulic excavators and backhoe loaders for lowering control devices during object lifting operations (installation manufacturer specified standard linkage): On machines that provide alternative linkages, only the standard lengths specified by the manufacturer are tested:

2 Normative references

The contents of the following documents constitute essential provisions of this document through normative references in the text: Among them, dated citations documents, only the version corresponding to that date applies to this document; for undated references, the latest edition (including all amendments) applies to this document: ISO 6165 Earth-moving machinery basic types identification, terms and definitions (Earth-movingmachinery-Basictypes-I- identificationandtermsanddefinitions) Note 1: GB/T 8498-2017 Identification, Terms and Definitions of Basic Types of Earth-moving Machinery (ISO 6165:2012, IDT) ISO 9248 Earth-moving machinery dimensions, properties and parameters of units and measurement accuracy (Earth-movingmachinery-Units fordimensions,performanceandcapacities,andtheirmeasurementaccuracies) Note 2: GB/T 21153-2007 Units and measurement accuracy of dimensions, properties and parameters of earth-moving machinery (ISO 9248:1992, MOD)

3 Terms and Definitions

The terms and definitions defined in ISO 6165 and the following apply to this document: 3:1 Linkage control system linkagecontrolsystem Hydraulic control components (including pilot servo valves) for lifting and lowering the lifting point when objects are hoisted: 3:2 Lifting linkage liftinglinkage The combination of components used to lift and lower the lifting point during the lifting of objects, such as the combination of a boom and a stick: 3:3 loweringcontroldevice A hydraulic control valve group used to control the lowering of the linkage mechanism when the hydraulic pipeline fails or ruptures: 3:4 failure-simulatingdevice Hydraulic valve block used to simulate failure or rupture of hydraulic lines in linkage control systems: 3:5 Signal oil circuit signalline Hydraulic circuit used to detect pressure: ...