Laboratory Testing & General Mineral Processing Engineering

Laboratory Testing & General Mineral Processing Engineering 2017-04-04T06:57:51+00:00
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Reducing Plant Downtime (3 replies)

John Koenig
2 years ago
John Koenig 2 years ago

When discussing the reducing plant downtime and considering increasing metallurgical plant uptime, it is essential to have a clearly understandable definition of the terms 'uptime', availability', 'utilisation' and others. In the example outlined above, the 95% 'utilisation' appears to be achieved after planned and breakdown maintenance downtime has already been subtracted. The true 'utilisation' figure from a cost viewpoint should include the 0% utilisation period during planned maintenance. The overall utilisation figure is the bottom line. For blast and electric arc furnaces, issues of cooling down and the time to get back on line mean that the planned maintenance downtime may be considerable, to minimise the very expensive risk of failure during a run. This is very different to a minerals processing plant, where the overall maintenance hours must be kept to a minimum, as well as minimising the risk of breakdown. Each shutdown must be carefully planned to ensure all required work is carried out, but no unnecessary work. This means condition monitoring, including oil analysis, vibration, temperature, with an excellent record-keeping procedure to enable shutdown planning for hours, manpower resources and spares. The issues for each operation need to be analysed to determine the causes of excessive downtime, for example: insufficient maintenance planning, insufficient condition monitoring, lack of spares or manpower resources, required skills unavailable, equipment reaching the end of useful lifespan. Equally, the reasons for low utilisation of a fully functioning plant require analysis, including lack of feed, lack of product storage, operator training, insufficient operations monitoring, failure of power and water services. Again, the term 'operational downtime' must be clearly defined. If the required resources and understanding of issues are not available within the project or parent company, outside consulting resources may be utilised, but the recommendations of consultants must also be carefully analysed!

Alan Carter
2 years ago
Alan Carter 2 years ago

For an American taconite plant processing very hard, abrasive iron ore, 95% "feed on" time to clock/calendar time is pretty much the standard, some plants do better. Pellet plants seem to run about 92 to 95%, and coarse and fine crushers about 80%. This is based on a 24 hour a day / 365 days a year time baseline.

The local operators have made a science, especially in the Concentrators, of controlling and designing for wear, hole patches made on the fly to last until downtime in launders and pipelines, extensive use of urethane liners and magnetic liners where appropriate, extensive research on crusher, mill, and pump liners, redundant equipment in key areas, rubber lined pipes, the list goes on. A local industry has developed for rubber lining pipes and boxes and casting some very creative urethane wear parts.

They are also creative, coming up with more permanent design changes to avoid chronic problems that keep showing up.

They also have to make full use of any downtime available, not stopping for only one problem but limping along or patching where possible until either downtime is scheduled for a main reason like a mill liner job, or at the least a full repair effort can be mounted to clear the work order list.

A lot is also preventive and predictive maintenance and inspections. Catching things that will wear out before the next down day. Developing a leaker list the day before a shutdown. That sort of thing. Full downtime is scheduled around major events like mill lining changes and coordinated between the Crusher, Concentrator, and Pellet Plant so that all can take advantage of the reduced demand for ore and availability of concentrate.

About 90% of the downtime is fixing wear related problems including things like mill liners, about 8% is mechanical breakdown of machinery, and 2% is lack of ore, mainly during storms in the winter.

John Koenig
2 years ago
John Koenig 2 years ago

Your comment shows exactly the situation is and what is required to keep on top of downtime in minerals processing plants. Attention to detail, innovation, data collection and analysis, excellent maintenance planning, above all interested and motivated people who actively seek continuous improvement in all aspects of the business. It should go without saying that positive management support and involvement is essential. Thanks for sharing your experience and insight.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

It was recently pointed out on another forum that plants with high reliability have both higher than average profits and fewer accidents, yet constantly the media and others harp on that those who plan and design efficient plants should be replaced by those who members of society who may seem to be "Under-represented" in the workplace.

We cannot have inexperience and higher production, or ship jobs overseas and expect to retain quality. "Cheap" has only short-term benefits.

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