Many people disagree as to the different types of maintenance and how to group them. The important thing is not being right about the definitions though but to know what entails what. First of all, there are two kinds of maintenance, preventive and corrective maintenance. The main purpose of the preventive types is to prevent any kind of failure. The ides is not only to preventive but to reduce consequences in case the failure does occur or even to asses risks and reduce them. With corrective ones, you wait until the failure is done and then the maintenance kicks in. This is just to restore the functionality of the equipment.
Preventive maintenance is done is regular intervals and the idea is to make sure the equipment is working as it should. We have established that the main purpose is to prevent but to also minimize any probability of failure happening. This can be based on time where they are done every week or month. This is not the only way they are done, they can also depend on usage for example number of cycles. There are different types of maintenance that fall into this preventive category.
The most obvious one is time-based maintenance. This one is done is fixed intervals and is regular. Just like every other type of preventive maintenance, the aim is to prevent any failure. This one assumes that all failures are age-related and taking preventive measures is important. One thing to note is that the condition of the equipment doesn’t matter.
The next one in line is failure-finding maintenance. This one is important because it looks out for hidden failures. You would not be able to see such failures easily unless you do this kind of maintenance. This will keep you on your toes but you also need to use it with another type of maintenance strategy.
Risk is not only likelihood of failure happening but the consequences that would follow that. When you have limited resources, you have to be very smart as how you allocate them. This is risk-based maintenance and the focus is on assets with the most risks.
Now, not all failures are age-related. You will find that most of these failures will show some sign. Condition-based maintenance is the answer if there is evidence that an asset is on the early stages of failure. This might stop the failure or reduce the consequences of failure.
There are more of the preventive types but there are also corrective ones. This ones, being corrective, waits until the failure is allowed to happen. Most times, when failure is allowed to happen, the consequences are not very significant. When the asset fails, it is them restored. This one includes deferred corrective maintenance and emergency maintenance.