Development of a Dragline In-bucket Bulk Density Monitor

This paper details the implementation and trialling of a prototype in-bucket bulk density monitor on a production dragline. Bulk density information can provide feedback to mine planning and scheduling to improve blasting and consequently facilitating optimal bucket sizing. The bulk density measurement builds upon outcomes presented in the AMTC2009 paper titled ‘Automatic In-Bucket Volume Estimation for Dragline Operations’ and utilises payload information from a commercial dragline monitor. While the previous paper explains the algorithms and theoretical basis for the system design and scaled model testing this paper will focus on the full scale implementation and the challenges involved. INTRODUCTION A dragline is a large mining excavator used in open cut mining to move overburden above coal. These machines excavate overburden from a blasted bench using a large bucket suspended by hoist and drag ropes. Properties of the blasted overburden have an impact on the total energy spent on excavation, dragline performance and maintenance. Accurate estimates of the bulk density are beneficial to the open cut coal industry as they can provide: 1. a reliable assessment of dig and blast performance, 2. an improved bucket size selection to achieve consistent suspended load targets, and 3. decreased production downtime by reducing probability of bucket overloads and subsequent damage to the dragline. This paper demonstrates a system for measuring the bulk density per payload in a dragline bucket during production. A prototype system was developed by CRCMining and trialled at Drayton Mine NSW. Particular interest in this paper is in the bulk density results and commercial prospects of this newly developed technology. In-bucket bulk density is measured using the payload weight and the bucket fill volume. Bucket payload weight is commonly available through commercial dragline monitors while in-bucket volume measurement is the gap in the prior art that this and preceding papers fill (Bewley et al. 2009 and 2011). 1 Department of Mechanical and Mining Engineering, The University of Queensland, CRCMining, QLD, Australia, 4067 2 School of Engineering Systems, Queensland University of Technology, QLD, Australia, 4000