Why Are We Simply Adding More Inspection And Replacement Tasks?
By Matt McLeod
At recent engagements, I have seen a trend towards adding more inspection and parts replacement tasks to the maintenance plan with little analysis to support these decisions. Across Bluefield, we’ve also observed that more inspection tasks mean PM checklists are becoming larger, which is making them ineffective.
My simplistic definition of asset management is: provide the required business outcomes at the lowest possible cost.
In our typical mining environments, the “required business outcome” generally relates to some measure of moving rocks from one location to another. More generally within industry, it will be some productive unit of measure, such as tonnes moved, litres pumped or units produced, often expressed as a rate per unit time – per hour, per minute, per day.
We should keep in mind that our physical assets have a primary function. I will use a production dozing example to illustrate my point.
Our production dozing system needs to supply a total of 2,200 tonnes of coal per hour to a feeder-breaker. Three Caterpillar D11R dozers are sufficient to deliver this quantity of coal (averaging 733 tonnes per hour each), but a fourth dozer is available to cover maintenance events. The dozers have a 120m push down a 1:4 slope. Blade load is around 67 tonnes. First pass is ripping the coal, second pass is pushing it to the feeder-breaker.
The engine is an important part of achieving this function. The engine function might be summarised as “propel dozer with 67 tonne blade load at 3km/hr down a 1:4 slope under control of the operator to achieve 733 tonnes/hour output”.
That’s it. If it affects the ability of the production system to achieve this goal, we – as asset managers – need to develop a management system that facilitates this function.
Do we care if the paint is peeling off? Only if it somehow – or eventually – affects the function. Maybe we have a goal to present the machines to a “high standard”, but this may not affect the function.
Do we care if the engine does not make rated horsepower? Yes, because low horsepower will affect either the blade load or the ground speed which affects the function of delivering 733 tonnes per hour.
The focus should always be on the function of the asset to provide the desired business outcomes.
Nothing that I have described above is new or revolutionary. It is simply the beginning steps of a Reliability Centred Maintenance (RCM) analysis.
RCM has been applied in aviation, the military and in general industry for decades now. It is not new nor is it a silver bullet. However, it is an important first step to help the asset manager “achieve the required business outcomes at the lowest possible cost,” which is the essence of an asset management plan.
It is agreed that inspection tasks are critically important to defect identification, however the task needs to detect deterioration in equipment condition that will negatively impact its function. If the defect is likely to lead to a functional failure that would result in unscheduled downtime, then it’s a valuable task.
However, if the immediate reaction to an emerging issue is to simply add an inspection, or worse still, a part replacement task without doing due diligence, then the result is a potential impact on the cost of operating that asset with no change to the function.
Replacement tasks should be reserved for wear-out items only. This should be carefully assessed and quantified via Weibull analysis. If the part is displaying infant mortality or random failure characteristics, there is no value in specifying a replacement task. The replacement task is adding cost to the asset for no improvement in its function.
Of course, there are extenuating circumstances and constraints in every business that impact our ability to manage our assets according to “theory”. We might have a labour shortage. We might have an expanding fleet and a lack of workshop bays. We might be better served grouping component replacement tasks due to their accessibility on the machine. With appropriate analysis, we can often demonstrate our modified approach is still providing the required business outcomes at the lowest cost.
Packaging and documenting inspection tasks is also critical. The task needs to be specific enough that any technician in your workforce can consistently assess the asset to the same standard. Even better, we should help that technician understand why we are inspecting any given part of the asset.
RCM techniques don’t have to be complex or start from a blank sheet of paper; Bluefield have experience in using them to develop practical equipment strategies. If you need help improving your asset management outcomes using RCM or any other technique, contact the Bluefield team to discover whether our experience can build your team’s performance.