GB/T 21938-2021Earth-moving machinery - Hydraulic excavator and backhoe loader lowering control device - Requirements and tests (English PDF)

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: […]