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Eight years into a mining career, my mind was blown by a presentation from a very experienced mentor. He introduced me to an extremely simple concept, and this minor change in thinking changed my entire outlook on mining. The presentation was on the theory of constraints.

Prior to understanding the theory of constraints, I always had a difficult time identifying what the “current” bottleneck of the operation was. I operated in a way which would maximise production in every area of the mine site, because “you could never get that time back”. Which is true to an extent - So what is the harm in doing that? The answer comes when you introduce the cost of producing and holding excessive inventory levels into your day to day thinking.

Inventory levels are difficult to manage in a mining environment. They de-risk the planned production output, but they also cost money to build and hold. So, best case would be to run lean on inventory to maximise profitability but not to the extent where production is at risk.

So, what is the theory of constraints? Simple! Here are the five rules you follow:

1. Identify the bottleneck constraint
2. Exploit the Bottleneck – maximise the utilisation of the constraint
3. Subordinate – Slow down everything else to save money. There is no point building inventory in front of the bottleneck if the bottleneck is already at capacity.
4. Elevate – increase the performance of the bottleneck.
5. Repeat – by making the above changes, the bottleneck might have changed.

But how does it apply to mining?

For me, I began to visualise the mine site I was working at not as a geologically complex, geometrically spread out beast - But more as a machine production line – which for me, looks like a series of gravity feeding grain silos. To illustrate, the diagram below shows a fairly typical coal mining process flow chart.

Once the process has been mapped as a flow chart, the next step is to understand the available inventory at each process. Inventory is the material which is available for the process (i.e. excavation). This is a good starting point in identifying where the operational bottleneck is. Lower than target inventory is a sign there may be a bottleneck in an upstream process.

Once the bottleneck is identified, you can either increase process utilisation to exploit the bottleneck, subordinate the system to work around the bottleneck constraint or elevate the performance of the bottleneck to improve the system performance.