Equipment, machines, systems, and installations have been evolving and changing over time, becoming increasingly sophisticated, requiring continuous improvement in maintenance processes and more rigorous work on the part of the maintenance manager.
Despite developments in equipment and facilities, maintenance needs remain the same. For this reason, and understanding maintenance as a set of technical actions to regulate the normal operation of these same pieces of equipment, we can divide it into three major groups: (1) Corrective Maintenance, also known as reactive maintenance or breakdown maintenance; (2) Preventive Maintenance, which is regular maintenance performed according to defined schedules, regardless of the condition of the equipment; and (3) Predictive Maintenance, or condition-based maintenance, which is based on the constant monitoring of the operating equipment and predicting the occurrence of failures.
In this article, we’ll explore the advantages and disadvantages of each of these types of maintenance and compare each of them with the alternatives.
What is Corrective Maintenance?
When a piece of equipment malfunctions, it must be repaired (or replaced!). This is the assumption of corrective maintenance, also called reactive maintenance. In other words, it is the technical activity performed after a malfunction has occurred and it is intended to restore the asset to a condition in which it can function normally, either by repairing it or replacing it.
As this approach is characterised by maintenance actions after a failure has occurred, it is ideal for low priority equipment, that is, assets whose absence won’t stop the company’s operations from continuing to function normally.
The same applies to equipment of lower value, as the work required to maintain or constantly monitor it can prove more expensive than repairing or replacing it when it breaks down. A simple example would be a lamp, which can be used until it melts and should then be replaced.
Given that very little planning is needed for this approach, its implementation cost is very low compared to the alternatives.
The problem is relying on corrective maintenance for medium or high priority assets. Since no preventive actions are taken in a Corrective Maintenance strategy, the lifetime of the equipment will end up being shorter than with one of the alternative strategies.
If applied to high-priority or high-value equipment (it shouldn’t!), it may lead to unexpected stoppages and possible huge repair costs.
We should not, however, mistake corrective maintenance with emergency maintenance, which occurs at different stages of a breakdown. While corrective maintenance is carried out at a time when certain physical damage or disturbance in the normal operation of the equipment is notorious (i.e. a functional failure), emergency maintenance occurs after total failure of the equipment, which requires urgent maintenance (and has generally higher costs).
What is Preventive Maintenance?
Preventive maintenance arises as opposed to corrective maintenance. Instead of waiting for the malfunction to occur, this type of maintenance aims to prevent it from happening.
Preventive maintenance occurs in a cyclical and programmed manner, regardless of the condition of the asset and in order to avoid malfunctions and minimise the consequences of equipment failures. The frequency is defined by the maintenance manager based on an estimate of the asset’s lifetime and the manufacturer’s recommendations. Examples of preventive maintenance actions include periodic overhauls, inspections, cleaning and lubrication of parts.
This type of maintenance is vital for high-priority equipment, which is needed for the normal operation of the company. In fact, the higher the risk associated with a particular malfunction, the greater the need for preventive maintenance to increase the asset’s lifetime and reduce unplanned downtime. A classic example is lifts or freight elevators — a failure in the elevator can be risky if someone is trapped; the repair may take a long time and an out-of-service elevator is always extremely cumbersome.
Because they are not based on the actual condition of the equipment, preventive maintenance plans can sometimes be inefficient and result in unnecessary maintenance (including replacement of parts) that cost time and money.
This effect is aggravated when a preventive approach is applied to low priority or low-cost assets whose simple repair on a reactive basis could cost significantly less.
Preventive Maintenance vs. Corrective Maintenance
Even taking into account the potential waste of preventive maintenance, these costs tend to be much lower than when repairing an asset only when there is already a functional failure. Strategies focused on preventive maintenance represent cost savings in relation to corrective maintenance. Some estimates point to savings between 40 and 60% annually when preventive maintenance is the focus.
Preventive Maintenance vs. Reliability-Centered Maintenance
Although there is a certain tendency to confuse reliability-centered maintenance (RCM) with simple preventive maintenance, they are not the same thing. In short, the aim of RCM is to increase the availability of assets. Obviously, this requires a major focus on preventive maintenance, but not exclusively.
There are several types of maintenance that fit into a strategy focused on reliability, including predictive maintenance, on which we will focus in the next few paragraphs. Therefore, although preventive maintenance and RCM overlap, they are not the same and should not be used as synonyms.
What is predictive maintenance?
Of all types of maintenance, this is the most recent and the one that requires the greatest investment in technology. The goal of predictive maintenance is to predict when a malfunction is about to occur. When certain undesirable conditions are detected, then a repair is scheduled before the equipment actually malfunctions, thus eliminating the need for costly corrective maintenance or unnecessary preventive maintenance.
It is based on the physical and operational condition of the equipment, through regular monitoring and testing, using advanced techniques such as vibration analysis, oil analysis, acoustics, infrared tests, or thermal imaging.
This approach is based on the physical or operational condition of assets instead previously defined statistics and calendars. The goal is to detect a potential failure while it’s still hidden, before there’s any visible signal.
Thus, the maintenance performed will always be better-informed, necessary and timely, since the equipment will only be subject to maintenance when a malfunction is predicted, which will reduce the costs and labor time spent on maintenance.
The need to invest in specific monitoring equipment, as well as in training staff to use it correctly and interpret the data collected, makes the implementation of this strategy very expensive, generally not within the reach of small and medium-sized enterprises. For this reason, it is not a cost-effective approach for assets that are not essential to the proper functioning of their operations.
Predictive Maintenance vs. Preventive Maintenance
Despite the high investment, predictive maintenance can represent large long-term savings. Predictive maintenance is more effective at detecting potential breakdowns than preventive maintenance and is more incisive to which actions are actually needed.
Take a look at our comparative article on these two types of maintenance to get a better understanding of the differences between them.
Predictive Maintenance vs. Condition-Based Maintenance
Many sources define predictive maintenance as condition-based maintenance. Although it is an understandable misconception — after all, predictive maintenance also evaluates the condition of each piece of equipment — we think it is important to make this distinction.
Condition-based maintenance focuses on well-defined analyses and parameters. For example, if after a visual inspection we detect something abnormal, we intervene. If the output of the equipment has decreased, then there has been a clear change in the device status and we should do maintenance. But predictive maintenance goes a little further by trying to detect faults at an even earlier stage.
What types of maintenance should it include in your strategy?
This is the million-dollar question. Unfortunately, there isn’t a recipe that all companies can follow to have the best results, regardless of the type of assets they have to manage. But now that you know the advantages and disadvantages of each, you can start preparing the right cocktail for yourself. In our opinion, the best strategy is to have a plan that incorporates the different types of maintenance, as appropriate for each type of equipment, according to its value and priority, and taking into account the investment possibilities of your company.
Computerised Maintenance Management Systems (CMMS) like Infraspeak exist to help you define, execute and monitor your maintenance strategy. If you are in doubt about investing in this type of system, read our article about 5 signs that you should invest in a CMMS, how a CMMS can help you save money, or how to choose the best CMMS for your team.