Underground » Maintenance
This ACARP project was mainly aimed at developing a computer-based tool to help operators of continuous miners and longwall shearers more accurately evaluate the reliability of picks in uncertain coal mining environments for optimal operation and maintenance. Rock properties and pick conditions often change within a range of values. It is hard to know the exact strength of an individual pick or a particular piece of rock during a mining process. To address uncertainty issues, a probabilistic method is needed to evaluate the failure risk of picks.
The following major tasks have been completed in this project:
· Collected data of picks, rock, drums and machines from four mine sites;
· Conducted pick bending, tensile and wear tests in laboratory;
· Investigated pick failure modes, causes and their distributions on drums;
· Developed mathematical models of the uncertainties of major factors including rock strength, pick body allowable bending force and pick tip strength;
· Developed a novel probabilistic pick failure risk assessment method; and
· Developed an Excel-based pick reliability assessment tool.
The collected data showed that the major pick failure/damage modes were pick tip damage (worn, snap-off, crack and/or chipping), pick body wear and pick body bending. While pick body bending was of major concern to one company, it was not an issue in other mine companies. The data obtained from field and laboratory tests confirmed that the rock property and pick condition, the two major factors affecting the pick failures, can have considerable uncertainties due to the nature of underground coal mining.
The developed Excel-based tool is easy to use and can generate the following outputs:
· Failure probability of a pick tip when cutting roof or floor;
· Failure probability of a pick body when cutting roof or floor;
· Failure probability of whole pick;
· Relationship between the overall failure probability of a pick, its attack angle and depth of cut.
This work enables operators to evaluate the reliability of picks in uncertain coal mining environments for optimal operation of the cutterhead, and determine the optimal operational parameters with which the pick failure risk control and the productivity can be balanced. The technique and tool developed is applicable to continuous miners and longwall shearers and roadheaders.