# A Machine Learning Framework for Condition-Based Maintenance of Marine Diesel Engines: A Case Study
### The Shift to Proactiveness in Maintenance
In summary, it is somewhere between RM and predictive maintenance, which is the latest trend based on emergent digital technologies (Internet of Things, cloud computing, data analytics). One particular form of prevention is what some researchers and practitioners call planned maintenance or scheduled maintenance [17; 18; 19; 20; 21], which some authors consider the most common onboard a ship [19]. It requires planning, documentation, and scheduling. The concept of planned maintenance is much used in industry, and is classically conceived to reduce the unexpected downtime by making all resources available as much as possible, according to a pre-defined strategy. Namely, regularly scheduled maintenance identifies and solves the issues that could become major problems. This is based on statistical observations such that, based on similar applications, maintenance is planned before the failure is likely to happen. Since the scheduled maintenance can be planned in advance, the need to react to breakdowns is quite uncommon. Moreover, the maintenance operations are faster and safer, because technicians know the procedures, the best practices, the parts to fix, etc. In this way, industry may optimize the running conditions and extend the lifespan of the equipment. However, the main challenge of planned maintenance is the costs associated with labor, potential downtime, parts, and the budgetary constraints. Moreover, it can lead to audits and operations that are not really required, increasing idle time and wasting money. Finally, note that the terms planned and preventive maintenance are often used interchangeably, but refer to two different things. PvM is the foundation for a planned maintenance strategy. Planned maintenance allows proactive management of facilities by encompassing both RM and PvM such that reliance on RM is reduced. It is often required for critical systems (e.g., regular inspection of a fire safety system) and many times is a condition to attaining permissions to operate. Until recently, maintenance operations, especially in shipping, were mainly performed by RM and PvM [22; 23; 24; 25]. Although many industrial manufacturers decide to use RM because maintenance is perceived as a negative necessary cost and investments in PvM are not seen as profitable, RM is today considered outdated. Namely, it was already found that an emergency repair costs three times and takes ten times longer than a scheduled maintenance task [26], and many industries are developing digital tools, automated systems, and prevention strategies to be competitive [27; 28; 29]. At the same time, PvM is widely used in the specific field of maritime applications, as recognized by experts in the field who discourage use of broken equipment on ships, also for safety reasons, as well as repairing broken machinery [27]. In detail, maintenance on ships or on shore is performed in three ways: (1) Emergency maintenance, only to repair equipment breakdowns, usually not at sea; (2) scheduled maintenance, especially on board ships, with periodic inspections and replacements, but highly expensive; (3) preventive maintenance, with various tasks and analysis of equipment conditions. Moreover, experts are in favor of early detection of failures and defects, which demands predictive maintenance. They also highlight that this new tool can be cost-effective with respect to preventive maintenance and can help in deciding (predicting) the next maintenance required for machines in service.