The maintenance, repair and overhaul or for short MRO of technical systems, construction elements, devices and operating material is intended to ensure that the functional condition is maintained or restored in the event of failure.
While the terms “inspection” and “maintenance” are summarized under maintenance, repair is divided into repair and overhaul whereby overhaul also includes improvements.
Objectives of maintenance
Maintenance of a trolley of a 5‑ton crane
Maintenance can be performed to prevent system failures. Other aims may be:
- Increase and optimum use of the lifetime of plants and machines
- Improvement of operational safety
- Increase of plant availability
- Optimization of operational processes
- Reduction of disruptions
- Predictive planning of costs
Maintenance is particularly important where the failure of technical systems irreversibly damages human life. In such cases, the monitoring of maintenance tasks is usually a sovereign task the state is responsible for, e.g. in the case of occupational safety. Due to the resulting costs, the associated safety regulations are regarded as a locational disadvantage or advantage in global competition depending on the interests involved.
Machine tools and production plants have enormously developed in recent years in terms of their design and technology. Therefore, it becomes increasingly difficult to capture the condition of individual components or assemblies as modern systems have considerably more weak points than it was the case with the original machines. In addition, designers no longer tend to oversizing but rather develop space-saving and lighter systems. However, a large number of components also react more sensitively to wear and tear as well as defects.
Today, maintenance and repair concepts primarily have the purpose of achieving the highest possible technical availability of the plant. More and more companies abandon the outdated attitude that maintenance is only a necessary evil or only a cost driver. The constantly increasing pressure in the competition for quality and productivity forces companies to introduce maintenance and repair systems in order to avoid undesired system failures. The internal know-how of the company is extremely important.
Knowledge is one of the most important sources for creating and maintaining competitive advantages, especially in maintenance. Although the basic structure of a maintenance system is due to standardized measures, a considerable degree of experience of employees or persons, who carries them out, will be essential. This is the only way that the timeliness of the applied measures remains ensured. In practice, problems often arise which have not yet been recognized by manufacturers. Thus, the employee knowledge is required to solve these problems and to evaluate the current system states as only someone who is experienced in using the machines on a daily basis can actually evaluate them.
A company must also consider the advantages or disadvantages of internal or external maintenance (outsourcing). Internal maintenance inevitably offers the advantage that the company’s own know-how about its own machines increases over time which would no longer be the case with external maintenance. When the maintenance work is handed over to maintenance companies, a high level of experience of the employees in using the machine is lost.
With the introduction of a preventive maintenance concept, the following objectives are set with regard to plant productivity:
- Few machine downtimes within one production time
- Short repair times of the machines
- Low impact of machine downtimes on the production flow
To achieve these goals, however, it is not enough just to define and carry out maintenance tasks; a smooth spare parts supply is also extremely important. However, the company should avoid high stocks of spare parts and only store those components as spare parts that are necessary to maintain the necessary machine availability, or make agreements with the plant supplier on the stocking of spare parts. Experiences such as the ordering frequency of certain parts are helpful. Also teleservice can help to minimize downtimes.
Source: German Wikipedia