The mining industry is a dynamic, exciting and an amazingly diverse sector with more than 120 occupations ranging from skilled trades to high tech professionals.
If mining is an industry you are considering a career in, have you considered what it would be like to be a Mechanical Engineer in mining?
Ray Wilson A Mechanical Engineer in mining in South Africa tells us all about his job.
By : Ray Wilson
“Mines come in many types and sizes. The Engineer’s role is complex and consists of many parts. Here is a description of one of them.
The mine, in this example, is a small underground diamond mine; mining a Kimberlite ore body called a “Pipe”. Near Kimberley, S Africa. The ore body is approximately circular and about 300m in diameter. It extends about 2000m deep; perhaps deeper.
It is mined via a rectangular shaft, of about 6m by 3m, 700m deep at this stage. The shaft has a process plant and sorting room in close proximity. The plant runs 24/7. The mine works only day-shift. There is a tailings dam about 2km from the plant. Processed ore, tailings, is pumped onto the dam where the tailings are separated from the water and the clean water returned to the process water ponds at the plant.
There is one winder, a Koepe friction winder that carries a cage. A long thin counterweight is used to assist the winder. The mass of the counterweight being slightly more than equal to the mass of the cage. In adjacent compartments two 7 ton skips work in counterbalance bringing ore to the surface. They are driven by a conventional double-drum winder (3MW).
Wesselton mine shaft headgear
The engineer’s day starts at 06h30 in the morning. He parks his car and walks to his office. On arrival he does a quick walk around the shaft bank and the plant to see what has developed overnight. He notes the previous days production and breakdown records.
He meets with the three foremen at 08h00 to discuss issues and work. There is a mechanical foreman for the winders, shafts and underground, there is a mechanical foreman for the surface plant and there is an electrical foreman for the entire mine. Each has several skilled artisans and aides reporting to them. The engineer is legally appointed to be responsible for the safe working of all machinery on the mine. (This includes the electrical plant as well.)
Therefore there are various scheduled activities that the engineer has to carry out. For example, weekly winder and rope inspections, weekly cage and skip inspection, monthly shaft inspections, underground working place inspections, shaft bottom inspections, shaft pump inspections.
View down the shaft taken during a shaft inspection
Ore is moved from the workings to the ore-passes by means of LHD’s (low haul dumpers). There are conveyors on the belt-loading level that must be monitored.
Belt loading level
There is a large jaw crusher situated on a level above the belt-loaders. This is the primary crusher; reducing the ore size to a size that can be conveyor by the skips. (about 150mm) Dust place, fitted with air-filters.
Main tramming level
On Wesselton, there is a lot of ground water that makes its way into the mine. This has to be cleaned by means of settling ponds at the lowest level of the mine. The clean water being pumped to surface in two stages, using multi-stage clear water pumps. The mud is pumped to surface using Gardner-Denver PA8 mud pumps. The man- winder and skip-winders are checked weekly to ensure that all safety devices are working. This is done by actual test. The cage, counterweight or skip is deliberately, slowly run though each trip to ensure that the trip is working.
In addition to this there is a SAP scheduled maintenance system in place. The foremen allocate the maintenance tasks to the artisans as required. Of course, there are many small breakdowns of equipment that are handled as they occur. These are handled by means of determining their priority. The most important first. The rope is inspected at the crossovers to monitor the wear at the crossovers. The Koepe winder ropes are checked to ensure each of the 6 ropes is taking the same load and to monitor wear.
Checking rope tension on the Koepe winder friction drum
Ore is fed into a stockpile bin at the shaft head. From there it is fed into a cone crusher, this is the secondary crusher. The smaller ore from this is fed into a Hazemag crusher which reduces the size further (now about minus 8 mm). The Hazemag works in conjunction with a screening tower. This ore is fed into a DMS system (Dense media system) which concentrates the ore. The concentrate is conveyed to the sorting house. Here X-ray machines remove the diamonds. Hand sorting then takes place. This is all done in the highest of security. There are cameras and guards all over the plant. Personnel are all polygraphed regularly to detect theft.
Wesselton DMS processing plant
The Tailings dams
Waste Processed ore from a diamond mine is called tailings. These are collected and pumped to the tailings dam as a slurry. On the top of these dams the slurry is distributed using spigot lines. The ponds allow the stream of slurry to slow down and the solid particles settle to the bottom. The clean water is collected via penstocks and pumped back to the plant for re-use.
Tailings dam spigot line discharging
The engineer’s role is to ensure the machinery is well-maintained, properly operated and kept in a safe condition. Written and photographic records are kept of all observations. It is a life full of challenges. One of the pros I have encountered are the men I have had under me. They were invariably very experienced, reliable and capable. Very good blokes. I lead by letting them use their own ideas, unless I see serious deficiencies in these ideas.
I let my men control their own maintenance budgets. I set their dollar monthly targets and we strive to achieve them. Cons are the lengthy breakdowns one can encounter. Often the engineer has to work for 30 hours or more without a break and without complaint (and without overtime pay) when a major piece of equipment fails. You have to lead by example.
During hard times, much pressure is placed on the engineer to keep producing with small budgets and reduced staff. This can be very stressful. This career is full of opportunities to use my creativity; designing machines and modifications I need for my machines. Then I get to build and commission them to. This is very satisfying.
This essay is a very brief overview of a rather complex role that the engineer plays on an underground mine. A more thorough expose will contain a lot more details; especially the scheduling of the legal inspection and maintenance work required. There are periodic inspections of these dams by the engineer. The results of these inspections are recorded in writing, Many photos are taken and as a record as well. The writer has many more photos of his observations on several mines and projects on file”.