What are preventive maintenance and predictive maintenance?

It is one of the worst-case scenarios for any company: Right in the middle of the production of an important order, the machine indicates a malfunction and there is a total breakdown. Production comes to a standstill, employees cannot continue working, and the order may not be completed on time. A technician has to be called. Weeks can pass before the problem is found and, if necessary, the correct spare part is ordered, delivered and installed.

Avoiding such a disaster is only one of the reasons for planned maintenance. Because the costs are difficult to predict, they can quickly threaten the company’s success, especially due to follow-up costs. There are still companies in which around half of all operating costs consist of maintenance costs. And that’s without even taking into account the loss of production or damage to the company’s image due to delayed deliveries. It is therefore logical that a well-coordinated maintenance process is essential for the profitability of the plant. After all, in the ideal case, all plants should always run as planned.

Basically, there are three different types of maintenance: corrective, preventive and predictive. Although we would like to focus on the latter two in this article, we will briefly look at all three for the sake of completeness:

If a problem or defect is detected in a piece of equipment, corrective maintenance is designed to get the equipment running properly again as quickly as possible. However, if repairs have to be carried out, this can not only be expensive at the time, but also massively disrupt production processes. It therefore makes sense to implement an alternative maintenance strategy.

It is not always possible to foresee and prevent all failures. However, the principle of so-called preventive maintenance helps to significantly reduce the probability of failures. In the best case, a failure of the plant can be prevented by replacing or repairing an impaired component in advance. Such “planned maintenance” can usefully be carried out at a time when it will cause the least disruption to the production process.

This is done using data from previous maintenance, which can be used to better estimate the service life of individual components. Computer-aided software makes it easy to keep track of all equipment and maintenance schedules and to coordinate measures. For example, colleagues can use the software to communicate with each other about the individual steps, components and procedures. In addition, a component that will be needed in the near future can already be purchased so that it is immediately available when needed. If a failure does occur, it can be easily recorded via the software and the information is always clearly and quickly available for the future.

Within preventive maintenance, differences are again made in the type and frequency of maintenance. If maintenance is simply carried out at regular intervals, we speak of routine or “time-based” maintenance. In this way, faults in the system can be found at an early stage. In the same way, this approach means that components are replaced that are still intact or whose failure would not endanger the system.

Among the different variants, the so-called “condition-based” maintenance is therefore the most economical. As the name suggests, this involves regular checks to determine whether the condition and performance of the plant acutely requires action. Only if a component is really in danger of failing is it replaced or repaired – so there is less waste from replacing parts that are still working. However, this constant monitoring by maintenance teams also costs many man-hours and is relatively complicated. This should be taken into account when choosing maintenance planning.

In contrast to preventive maintenance, predictive maintenance eliminates the need for personnel to carry out constant checks. Instead, this innovative variant works with large data sets that are automatically recorded, stored and analyzed. As part of Industry 4.0, it is thus possible to predict with great precision when a component needs to be replaced on the basis of numerous different sensor data from the plants, such as temperature, speed, humidity, etc. The data is stored and analyzed automatically. All necessary measures are then taken in advance: The right personnel are scheduled, parts are ordered and suitable time periods are reserved.

Predictive maintenance thus makes it possible to prevent high costs due to production downtime, avoid accidents and reduce unnecessary storage times for spare parts. In addition, this precise maintenance should increase the service life of the equipment and optimize the impact on the environment.

How exactly can this work? Predictive maintenance involves using special systems to constantly check the condition of the plant by connecting it to the Internet. This should enable maintenance to be carried out not only at the best time, but also in a cost- and performance-efficient manner. However, the upfront effort is expected to be high: the company must ensure that the necessary data is collected, digitized and transmitted. In addition, the necessary infrastructure for storing and analyzing the large volumes of data must be in place. In addition to storing the data, which can be in a wide variety of formats, an intelligent algorithm is needed to analyze and evaluate it. If all this is in place, predictive maintenance can bring numerous advantages for the company.

Predictive maintenance has now arrived in many areas – not just industrial ones. For example, it makes it possible to almost completely eliminate downtime in the field of wind turbines. Also in aviation, it is remarkable what can be achieved through predictive maintenance: For example, the condition of the aircraft’s components is analyzed continuously and fully automatically. If a part has reached the wear limit, an order is automatically sent to the arrival airport – while the aircraft is still in the air – where a technician is already waiting with the spare part on arrival. The time the aircraft is on the ground is reduced to a minimum.

Which type of maintenance makes sense for which company depends on many different factors and should always be considered carefully in each individual case. However, those who are open to innovative, software-supported methods can sustainably strengthen their company, employee satisfaction and the environment.