Loaders – at the frontline of mining operations

By Dmitry Przhedetsky*

In all types of mining operations utilising loaders, they work at the very frontline, hence are the most exposed to roof, wall and bench failures.
A range of other operating conditions contribute to a tough life of loaders, such as rough road surfaces; rock debris; ground water and human error. Surveys of operators’ habits and preferences have found that operating practices vary more than that of other types of equipment (e.g. trucks), which all contributes to faster wear and tear of loaders.
Developments in remote controlled loaders have not eliminated this factor. The line-of-sight remotes have limitations and do not always guarantee the safest operator position. Teleremotes allow you to operate the loader from a crib room however still do not protect the loader itself from the human error and occasional abuse.
Automated (also called Autonomous) loaders, while already adopted by some mines, operate slower due to the fact that operations are restricted to the first gear only. They are subject to faster wear and tear as the road bumps, ruts and spillage, which would be normally be mitigated by an operator, directly impact on the tyres and transmission. Nevertheless, the automated loaders are a step forward and further developments are in the pipeline.
Loaders themselves have been going through continuous improvement. One of the major advantages of the modern loader is its ability to achieve a full bucket in a single pass, without racking the pile or multiple passes. Higher breakout force due to z-bar (vs. old parallelogram) boom geometry along with high shape bucket factor will reduce cycle time substantially.
When the loading cycle is optimised, a loader should be able to load a mine truck in three passes. If it doesn’t, either the truck will be underutilised not carrying 100 per cent of its payload, or the loader will need to make the fourth pass. This will prove to be the most unproductive part of the cycle, as the loader won’t be carrying the full bucket over almost the same amount of time it would spend on a full bucket. Hence it is advisable to have a few buckets of different size for the ore bodies with alternating ore (or mullock) density at different levels. This will allow you to increase the utilisation of trucks and loaders and also to avoid overloading them.
As cleaning out the ore is often a race against time due to the risks described above, safety and reliability of the loaders is another critical part of operations. While there will be different requirements for low profile underground coal loaders versus large loaders operating in open cuts and quarries, one thing is common for both: there is no compromise on operator comfort and serviceability of the loaders.
Implementation of self-lubricating pins and split-cap mounted pin connectors has extended the service intervals and simplified the procedures. There have been many improvements to diesel engines and transmissions, as well as advancements in controls and safety features.
Nevertheless, everyone knows that the tyre life of loaders in most cases could amount for only half of that of an underground truck. Bucket lip may need hard facing on a weekly basis. Operators are exposed to higher fatigue due to continuously changing movements within a loading cycle and their harsh impact on the body. Meantime-to-failure of some components will change once a loader is moved from development to production etc.
The manufacturers of loaders have been able to address many of these issues over the recent years however one thing has not changed: loaders still work in the most risky environment at any mine site. Their life expectancy is shorter than perhaps other pieces of equipment on site.
The cost of loaders along with the amount of parts and service required for their ongoing operation as well as the small number of manufacturers, means that the market for loaders one of the most reliable in the mining game.

* Dmitry Przhedetsky (M Eng (Mining), FAusIMM) is a director of Rock Cognition Pty Ltd. Contact him at: dmitry@rockcognition.com.au