The following is adapted from Simplifying Mining Maintenance.
When it comes to equipment maintenance, scheduled downtime is the key, it is the only thing that we have control of. We know when it will occur, what will be done and how it will be done.
Scheduled downtime, executed to adequate quality standards, helps reduce costly and disruptive unscheduled downtime. You want to ensure that your scheduled downtime—by which I mean shutdowns and routine scheduled service outages—is effective and efficient. It should never be cut short in an attempt to improve availability.
Scheduled downtime is often reduced to increase the availability of equipment. Unless you control unscheduled downtime first, reducing scheduled downtime is a mistake.
To determine whether a site should reduce scheduled downtime, I look at the amount of scheduled downtime, unscheduled downtime, and the target availability. I want to see how much scheduled downtime there is and how this compares to our benchmarks for mobile and fixed plant. If the scheduled downtime is right but the unscheduled downtime is excessive, then it is best to target these unscheduled delays first.
Most times, you must first correct the execution effectiveness or execution quality standards before you can reduce scheduled downtime. It is true that you can work on reducing both scheduled and unscheduled at the same time, although you must recognise that they require different actions to make improvements.
There are sites that are doing the basics well and achieving low levels of unscheduled downtime. If your site is doing quality work with around 60% scheduled downtime for mobile equipment and 70% or higher for fixed plant, then you have the chance to optimise the scheduled downtime. The changes must still also allow for the same amount of work to be done at the same quality standards, but with less scheduled equipment downtime.
What causes excessive scheduled downtime?
Excessive scheduled downtime typically results from problems with planning and scheduling. We invented planning and scheduling to make our scheduled downtime events more efficient and to give our workers the information they need to do a better job. Planning and scheduling can have some effect on unscheduled downtime, but only if execution standards are high. The goal should be to get more work done efficiently in less scheduled downtime with processes that facilitate repeatability and precision.
Scheduled downtime events need to be planned in detail and should include an assessment of what could go wrong with each task. We then have the opportunity to identify how to avoid those potential delays or at least have a contingency.
When you analyse the challenges that disrupt scheduled downtime, you repeatedly find the same issues—most of which can be avoided. Here are some problems that lead to excessive scheduled downtime and how to solve them.
Problem #1: No scheduled-downtime strategy
When a maintenance team develops a strategy for a machine, the first thing it must do is look at the required maintenance tasks to be performed over its life cycle. Then the team must fit the tasks into a repeatable sequence of scheduled-downtime events and what the resulting scheduled downtime of the machine will be across its life cycle.
When our company starts a project on a site that is not achieving its availability targets, we almost always find that there is no formal scheduled-downtime strategy.
People generally know when the machines are shut down, but there has been no attempt to control the amount of scheduled downtime in a logical manner that allows sufficient time to complete the required work and optimise the downtime.
When there is no routine downtime strategy, the site will often take scheduled windows in an ad-hoc manner, which will lead to unnecessary downtime.
To successfully implement a strategy like this, both maintenance and operations teams must agree to it. This agreement allows maintenance and operations to optimise the downtime over the longer term. This scheduled downtime strategy also forms the core part of the asset management plan that we document for each machine type.
Once the downtime windows are scheduled in the weekly planning process, sites can’t delay or wait for an opportune window in the production schedule to do the work.
If you wait for a break in production to do scheduled maintenance, the required resources are often busy on other tasks and mechanics can’t maximise their work on the idle machine. Instead, managers must provide access to the plant in a scheduled manner if they want the maintenance crew to stay on top of developing defects.
They must follow a logical, scheduled downtime strategy.
Problem #2: Defects are not raised with sufficient lead time
Everything that could cause a machine to break down before the next scheduled service must be fixed before it’s put back to work. However, not every problem needs to be repaired on the spot. Instead, some defects should be raised in the system and scheduled for the next event when the parts and labour required to execute the job can be planned and scheduled. This is more efficient than doing emergency repairs.
For example, a worker notices wear on a hydraulic hose. He thinks he needs to replace it, but he doesn’t have a spare hose. So he goes to the warehouse and gets one. Then he must find time to replace it within the scheduled downtime event.
However, if the hose wear is so bad that it needs to be replaced immediately, then the wear should have been noticed and a work order raised in the system during the previous service, when the problem was less severe. By waiting until something had to be done, the maintenance team have caused an extended scheduled downtime event.
This type of problem can be corrected if the team has daily discussions to discuss these types of events and to agree on how they will be avoided in future.
Maintenance teams also must be clear about tolerable defects. Not everything has to be fixed on the spot. Remember how the airline industry has detailed limits on such things as drips per minute? Some leaks are tolerable and can be fixed at the next scheduled maintenance, but you have to be aware of the leak in the first place. The mining industry needs to follow the example of the airline industry and ensure all defects are raised and tracked so there is sufficient lead time for the repair to be planned and scheduled.
Problem #3: Worthless pre-service inspections
Pre-service inspections, which look for equipment defects three or four days before the equipment comes in for scheduled service, are a waste of time.
This strategy does not allow people to plan ahead. What’s more, operators perform daily inspections on their machines, so a pre-service inspection is either redundant or an admission that operator inspections are not being done correctly. The preservice inspection adds scheduled downtime that isn’t necessary.
Problem #4: Cycling between planning methods
Centralized planning means all the planners work on one team with a planning function lead or superintendent. Decentralised planning means the planners are part of the same team as the supervisor and both report to the same superintendent. Many companies have centralised their planning functions, but clients still ask questions about whether centralised planning is better than decentralised planning. In years to come, I’m sure there will be a push to decentralise planning again as the cycle continues.
Both structures have problems. Centralised planning has problems with communication between the planning and execution functions. If the superintendents of those two functions don’t work together and communicate well, the manager has to step in. This often creates more work for the manager. When planning is decentralised, you only have one superintendent to go to in order to get better performance from the plant.
In the decentralised model, planners get roped into helping fix breakdowns. They stop planning and become resources for execution. In addition, decentralised planners often do things differently, causing inconsistent planning approaches across the business. When this occurs, managers want to centralise the planning function to get it in control, which introduces communication problems and removes single-point accountability.
The structure doesn’t matter if people commit to making the equipment perform. In fact, restructuring creates a mask; it doesn’t solve the problem and often creates confusion. It’s more effective if you set up the right communication processes. Regardless of the model, planners and supervisors must discuss (in either a meeting or in informal conversations) what went right and what went wrong. There must be formal weekly or daily schedule-review meetings, but informal discussions are equally important.
For more advice on scheduled downtime for mining equipment, you can find Simplifying Mining Maintenance on Amazon, Play Books and www.simplifyingminingmaintenance.com.
Gerard Wood is one of the mining industry’s foremost authorities on proper mining equipment maintenance. In his long career, Gerard has been all over the world, working his way up from an electrician’s apprentice to a maintenance manager with advanced degrees in electrical engineering and business. As managing director for Bluefield AMS, Gerard helps the world’s largest mining companies keep their machines running with a simple, practical approach that saves money and improves equipment reliability.