ACARP ACARP ACARP ACARP
Open Cut

Stress Relieving and Pre-Fabricated Nodes for BE Dragline Booms

Open Cut » Maintenance & Equipment

Published: August 05Project Number: C13045

Get ReportAuthor: Daya Dayawansa, Brian Kerezsi, John Price, Ana Paradowska | MTI, Monash University

A previous ACARP project (C11052) identified weld quality and residual stresses as two major factors contributing to poor fatigue life of BE boom clusters compared to Marion clusters. The traditional fabrication methods that have been used for decades without much improvement are responsible for both these factors. Surprisingly, according to the current practice, the main chord butt welds that have comparatively more favourable conditions from residual stress and weld quality view points are stress relieved, while the clusters that generate more than 90% of fatigue problems are not stress relieved. Stress relieving is expected to improve fatigue life of clusters significantly, and as part of this project sound procedures for cluster stress relieving have been developed and successfully trialled on a BE boom.

Stress relieving in-situ can have other effects such as structural deformations, material property changes, etc. These effects were comprehensively examined though the laboratory and field trials undertaken as part of the project. The results indicate that stress relieving of BE boom clusters can be undertaken safely to improve the fatigue performance of the clusters. 

The investigations found that stress relieving also had other benefits such as tempering the weld material and also reducing the hardness of welds. These improvements will also contribute to improving the resistance to initial growth of cracks under load by improving the toughness of the steel near the welds. 

The following specific conclusions were made from the cluster stress relieving investigation:

  • Stress relieving can significantly reduce the unfavourable axial tensile residual stresses in a cluster. Following the recommended procedure in the report, the residual stress levels can be reduced at least by 40%.
  • Stress relieving the clusters as recommended can increase the fatigue life of clusters at least by 50% and possibly up to 100%. 
  • The cost of stress relieving a pair of clusters (i.e. A and B chords) varied between $3-5k. During the field trials at Blackwater mine, stress relieving of six pairs of clusters were undertaken with no addition to the overall shutdown duration.
  • Stress relieving also has a beneficial effect on the hardness of welds, reducing them to acceptable levels. This will also contribute to longer fatigue life of clusters.
  • The procedure adopted for stress relieving of clusters generally conforms to AWS D1.1:2000 Structural Welding Code – Steel [6].
  • The adopted stress relieving procedure has no significant influence on the microstructure of the steel used in the boom. The material tests showed that the influence of stress relieving on the other material properties such as the yield strength of the parent material is small, and therefore should not significantly affect the strength of the boom.
  • Based on the findings of the investigation, stress relieving of clusters is recommended for all new clusters in BE booms.

When clusters are replaced after several repairs, the conventional approach is to cut off ~2m length of main chord covering the cluster and replace it with a new main chord segment, and then weld all the lacing pups in-situ to complete the cluster. This approach results in poor weld quality and high levels of residual stresses, and also contributes to longer shutdown durations. Using the latest techniques in surveying and accurate fabrication methods, it is possible to prefabricate the clusters under shop conditions, stress relieve them under controlled conditions, and complete only the attachment welds under field conditions at less critical locations.

The project investigated the feasibility of pre-fabricating the clusters with higher weld quality standards, stress relieving them under well controlled conditions and then attaching them to the booms during shutdowns.  This procedure can reduce the downtime of the machines and also significantly improve the fabrication quality of the clusters. The investigation concluded that the pre-fabrication of clusters is technically feasible to implement on a dragline boom.  However, a field trial could not be undertaken as an opportunity to implement it on an actual dragline boom could not be found. Some of the measuring techniques were trialed on a cluster manufactured in the laboratory.  

Underground

Health and safety, productivity and environment initiatives.

Recently Completed Projects

C28026Measuring The Height Of Fracturing Above Extracted Longwall Panels To Improve Reliability Of Groundwater Impact Predictions

Longwall mining is a mining method widely used in the Australian und...

C25059Development Of An Intrinsically Safe, Integrated Wireless Communications Network With A Distributed Array Of Geotechnical Sensors

For over 20 years, SCT Operations (SCT) have provided a range of ind...

C26051An On-Machine Bolting And Geotechnical Monitoring System

The primary objective of this project was to investigate how laser s...

Underground

Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C27046Estimation Of True Deformation Vector From Slope Radar Monitoring

Slope deformation radar monitors are now widely used in open cut coa...

C29003Wear Debris Removal From Dragline Commutators

The original aim of this project was to establish a method of removi...

C28037Local Scale Dispersion Modelling To Support ACARP Emission Factors

There remains significant concern in the industry regarding the accu...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27032Coal Grain Analysis Applications Handbook

This Handbook sets out recommended practices for using coal grain an...

C26012Improved Flotation Recovery Via Controlling Froth Behaviour

There is no real-time measurement for coal flotation performance, ma...

C27012Towards Better Fine Coal Classification

It is well recognised that the efficient classification of fine coal...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

C27008Selective Absorption Of Methane By Ionic Liquids

The connection of a ventilation air methane (VAM) abatement plant di...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community

NERDDC

National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook

NERDDC