What is Preventive Maintenance?
Preventive maintenance arises as opposed to maintenance planning. Instead of waiting for the malfunction to occur, this types 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. 

Advantages
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.

Disadvantages
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.