There are numerous seminars, articles, and workshops that explain strategies which help you maintain your machines. In this article, we are going to help you choose the most appropriate strategy that will increase the effectiveness of your maintenance program, reduce labour hours, increase equipment availability and ultimately reduce costs.
Maintenance professionals around the globe believe that the choice of these strategies should always be based on two key factors – the right time and the right place. This conclusion comes from years of experience in working with maintenance shops and studying a variety of industries. There are five main strategies; they can be described as given below.
Preventive maintenance is a very old maintenance strategy that represents periodic maintenance as a deterrent against unscheduled or unplanned maintenance. In this strategy, maintenance professionals work at predefined intervals of time such as hours or days; or based on usage such as the number of repetitions or miles travelled. This strategy doesn't take the condition of the oil or equipment's performance into account while performing maintenance; they are only reviewed to set guidelines for the frequency of maintenance. This is a relatively easy strategy to set up and execute, but it may prove to be expensive eventually as it ignores other factors that affect a machine’s productivity
Predictive Maintenance is similar to Preventive Maintenance with one key difference. It assesses the condition of the system and predicts failure before it occurs by the use of noninvasive testing. It utilizes thermal imaging, vibration analysis, ultrasound analysis and oil analysis to judge the time and manner of maintenance required. Additionally, it monitors the work order history, the amount spent on minor repairs, number of operator complaints and the frequency of these repairs to calculate the cost savings from reduced man-hours spent on maintenance. This strategy might seem like the perfect one, as it doesn't try to fix anything that is not broken, but it has its disadvantages. The cost and labour requirements for predictive maintenance may prove it to be less profitable than other, less comprehensive strategies.
For example, let’s consider the maintenance requirement of a gear pump which is attached to a minor circuit. In this scenario the cost of replacing the gear pump is minimal and the pump is readily available. The pump has a small oil capacity; there are no safety concerns and no impact on production in case of failure. In this scenario, the "run to failure" approach would be much more suitable than Predictive Maintenance approach.
Although this may not sound like a strategy, run to failure is the correct maintenance decision in some cases. If your equipment is at the end of its lifecycle, you would simply want to utilize it as much as possible before its inevitable breakdown. While going for this approach, ensure that you have a replacement ready on-hand and are prepared for the failure so that other components are not affected. To minimize disruptions to the system when the failure occurs, it is helpful to do nondestructive testing well in advance.
This maintenance strategy can be used with any other strategy as a combination of the two. However, it is also considered a stand-alone maintenance strategy by many. This strategy requires analysis of potential threats to the system as well as the analysis of malfunctions that have already occurred in the past. It requires root cause analysis rather than symptomatic analysis; like verifying if the lubricant was incorrect, whether the rebuilding procedure is faulty or there is insufficient contamination control, etc. Then one can focus on eliminating these issues to ultimately extend the lifetime of the component.
Reducing or eliminating reactive maintenance is the goal of every maintenance program. These unscheduled and unplanned events disrupt your schedule for the day and mostly result in monetary losses. Regardless of which maintenance strategy you choose, these unplanned events happen and often lead to an unpleasant visit from the plant manager, owner, customer or operations superintendent. Reducing reactive maintenance should always be a plant’s goal; this can be achieved only by continuously improving the maintenance strategy followed in the plant.
Do an honest evaluation of your present maintenance program and try to identify areas that need improvement. Analyze all the major maintenance activities and repairs you perform on a routine basis and find out the average cost of a planned/scheduled event. Evaluating this amount by comparing it with an unscheduled maintenance event, will present you with its cost-effectiveness. The cost of executing a maintenance strategy should always be less than that of reactive maintenance.
For evaluating your current maintenance strategy with respect to other possible strategies, check whether you are facing the following issues:
1. Frequent unplanned or unscheduled maintenance event.
2. Completing all of the scheduled work on time is difficult.
3. Exceeding maintenance budget and having cost overruns.
4. Reactive maintenance affects your production.
If you have encountered any of these issues in your plant, you need to reevaluate your maintenance strategy as soon as possible. The best way to do this is to monitor Key Performance Indicators (KPI) to find out the effectiveness of your current maintenance program and then do a GAP analysis with your desired maintenance effectiveness threshold. This information will enable you to make informed decisions on the type of maintenance strategies you should implement. Remember that the needs of your machines and your organization change with time, what works today may not work tomorrow, so it is important to periodically analyze the effectiveness of your maintenance strategy.