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Logo of the German Institute for Standardization DIN 31051
Area maintenance
title Basics of maintenance
Latest edition 2019-06
Logo of the German Institute for Standardization DIN EN 13306
Area maintenance
title Maintenance - terms of maintenance
Brief description: German, English and French versions
Latest edition 2018-02

According to DIN EN 13306 and DIN 31051, maintenance is the combination of all technical and administrative measures, as well as management measures during the life cycle of an object, which serve to maintain or restore its functional condition so that it can fulfill the required function.

The concept of maintenance has been defined differently in national and international standards and regulations to date. For this reason, the European Committee for Standardization ( CEN ) has recognized the need to standardize the definition of the basic terms for all types of maintenance and maintenance management - regardless of the type of object considered - with the aim of drafting a comprehensively structured standard that contains the main terms, including their definitions, in the form of a maintenance dictionary. In order to avoid double and multiple standards, only EN 13306 should be used for the definition of the term. The maintenance of software only is excluded from this standard. DIN 31051 was last updated in 2019 and should be withdrawn at the next review in order to be replaced by DIN EN 13306 as a national standard.

While older technical standards and regulations under maintenance primarily describe technical measures in order to maintain the functional reliability of an object in the long term, the maintenance requirements have changed in that maintenance is not limited to technical measures alone, but also administrative measures such as Planning, handling of documentation, analysis, feedback and much more. Maintenance is no longer just a specific sequence of measures, depending on the standard used, but rather represents the process of maintenance management tailored to the respective situation.

The European standard EN 13306 defines the basic terms for the technical and administrative areas as well as for maintenance management. DIN 31051 and DIN EN 13306 currently still differ in terms of both structure and use of terms. While DIN EN 13306 structures according to types of maintenance and maintenance activities, DIN 31051 divides maintenance into basic measures, which, however, does not contradict the requirements in DIN EN 13306. Furthermore, the term “wear reserve” is defined in DIN 31051, which is still missing in the terminology of DIN EN 13306. After the content of DIN 31051 has been implemented in DIN EN 13306, DIN 31051 will be withdrawn.

Normative references

The DIN standard DIN 31051 structures maintenance into four basic measures

  1. maintenance
  2. inspection
  3. Repair
  4. improvement

The DIN EN 13306 divides the maintenance in the two categories

  1. Preventive maintenance
  2. Corrective maintenance

Maintenance objectives

Maintenance of a trolley of a 5 ton crane

Maintenance can be carried out to prevent system failures. Further goals can be:

  • Increase and optimal use of the service life of systems and machines
  • Improvement of operational safety
  • Increase in system availability
  • Optimization of operational processes
  • Reduction of disruptions
  • Forward planning of costs

Maintenance is particularly important where the failure of technical systems causes irreversible damage to human life. In such cases, the monitoring of maintenance tasks is usually a sovereign task that is the responsibility of the state, as is the case with occupational safety , for example . Because of the resulting costs, the associated safety regulations are viewed in global competition as a location disadvantage or a location advantage, depending on the interests.

The maintenance of aircraft is particularly precisely regulated.

Maintenance today

Machine tools and production systems have developed enormously in their structure and technology in recent years. It is therefore becoming more and more difficult to record the condition of individual components or assemblies, as there are significantly more weak points to be found in modern systems than was the case with original machines. In addition, designers no longer tend to oversize, but rather develop more space-saving and lighter systems. However, this means that a large number of components also react more sensitively to signs of wear and defects.

Today, maintenance and repair concepts primarily have the task of ensuring the highest possible technical availability of the system. More and more companies are abandoning the outdated view that maintenance is just a necessary evil or just a cost factor. The constantly growing pressure in the competition for quality and productivity is forcing companies to introduce maintenance and repair systems in order to avoid unwanted system failures. In-house know-how is very important here.

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 can be traced back to standardized measures, a considerable amount of experience on the part of the employees or those carrying out the work is essential. This is the only way to ensure that the measures applied are up to date. In practice, it is not uncommon for problems to arise that the manufacturing companies have not yet recognized. Here, the knowledge of the employees is required to solve these problems and to evaluate the current system status, because only someone with experience in daily use of the machines can evaluate them.

Here a company must also ask itself the question of whether it is in-house or outside maintenance ( outsourcing ). In-house maintenance inevitably has 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 the maintenance company, a high level of experience of the employees in handling the machine is lost.

The market for industrial services in Germany

In 2016, the following providers largely determined the German market for industrial services:

rank Companies Sales in Germany in million euros Number of employees in Germany
1 Bilfinger SE , Mannheim 1,004.0 08,961
2 Wisag Industrie Service Holding GmbH, Frankfurt am Main 740.0 13,000
3 Remondis Maintenance & Services GmbH, Cologne 1) 670.0 05,200
4th Leadec Group, Stuttgart 2) 438.0 07,583
5 Kaefer Isolation Technology GmbH & Co. KG, Bremen 335.0 03.210
6th Weber Unternehmensgruppe GmbH & Co. KG, Pulheim 262.0 01,830
7th Hertel Industrie Service GmbH, Lingen *) 260.0 0.0987
8th Kiel Industrial Services AG, Wesseling 185.7 01,621
9 Babcock Industry and Power GmbH , Oberhausen 3) 155.8 01,124
10 InfraServ GmbH & Co. Knapsack KG (today YNCORIS GmbH & Co. KG), Hürth 113.5 0.0783

1) Part of the Remondis Group and shareholders of the Xervon and Buchen group of companies, which have been reporting on a consolidated basis since 2014

2) formerly Voith Industrial Services: sales and employees of Leadec and Veltec

3) Including sales and employee numbers of the Ritter Group and Bachtrup GmbH

*) Data partially estimated

Inclusion in this ranking is subject to precisely defined criteria. At least 50 percent of domestic sales are generated with industrial services (maintenance services in accordance with DIN 31051, plant and machine cleaning, scaffolding, pipeline construction, etc. in both the process and manufacturing industries without plant construction, software sales or energy management / energy supply services). No OEMs ( Original Equipment Manufacturers ) or industrial parks, no power plant services. At least 66 percent of sales result from external orders.

The Lünendonk & Hossenfelder GmbH considers continuously the market for industrial services in Germany since in 2009. As industrial services, it defines the services that are provided in accordance with DIN 31051. This includes diagnosis, maintenance, inspection and repairs. The market research company does not claim to represent the entire market. Rather, it focuses on looking at the leading providers in a given market segment. In addition, some medium-sized and small industrial service providers are included in the analyzes for comparison purposes. Together, these companies represent the basic structure of the market and such high sales shares that it is possible to draw conclusions for the overall situation and development.

Preventive maintenance

With the introduction of a preventive maintenance concept, the following goals are set with regard to plant productivity:

  • few machine downtimes within one production time
  • short repair times on the machines
  • low impact of machine downtimes on the production flow

In order to achieve these goals, however, it is not sufficient to simply define and carry out maintenance tasks or to carry out regular inspections; a smooth supply of spare parts is also of great importance. 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 arrangements with the system supplier about the provision of spare parts. Empirical values ​​such as B. the ordering frequency of certain parts is helpful. Also Teleservice can help to minimize downtime.

Maintenance strategies

In addition to the technical aspect, there is also the consideration of the operating costs that arise for the maintenance and repair area. In the event of a machine failure, a company in series or mass production not only incurs the costs that arise from possible repair work or new acquisition of defective components, but during the failure the company cannot continue production on the failed machine. Adherence to deadlines and maintaining product quality play a very important role.

Different strategies are used in today's maintenance. The most important strategies are:

  • Repair after failure: No preventive maintenance is carried out. The failure is accepted and errors are corrected after they occur. A typical example is the replacement of (non-critical) lamps after a defect.
  • Planned maintenance: There are preventive measures to minimize the risk of failure. A distinction is made between:
    • Predetermined maintenance: Preventive measures (such as inspections and maintenance) are carried out so that measures can be taken before a fault occurs. On the one hand, these activities can be time-based. However, strategies are also used that are based on other criteria (such as running times, quantities). A typical example is the oil change at fixed intervals or after a certain mileage in internal combustion engines of motor vehicles.
    • Condition-based maintenance: The wear-related conditions are recorded. This is done either permanently, for example by sensors (e.g. in the form of condition-based maintenance ) or inspections by humans. The corresponding wear and tear stocks are recorded and compared with the necessary wear and tear stocks for safe plant operation. If this falls below a minimum value, the maintenance measure for the respective component is carried out. An example of this is the replacement of car tires when the prescribed minimum tread depth of 1.6 mm is not reached.
    • Prospective maintenance: The prospective maintenance strategy already starts in the planning phase and thus determines with foresight - i.e. H. prospective - the optimal point in time for planned maintenance measures or even entire bundles of measures.

Maintenance terms

According to DIN 31051: 2003-06, maintenance is defined as:

"Combination of all technical and administrative measures as well as management measures during the life cycle of an observation unit to maintain the functional condition or to return it to it so that it can fulfill the required function."

"The maintenance can be completely subdivided into the basic measures maintenance, inspection, repair, improvement, weak point analysis."

Further terms are (according to DIN 31051: 2003-06):

  • Maintenance : Measures to delay the depletion of the existing stock of wear and tear (continued)
  • Inspection : Measures to determine and assess the actual condition of a unit under consideration, including determining the causes of wear and tear and deriving the necessary consequences for future use (continued)
  • Repair : Measures to return a unit under consideration to the functional condition, with the exception of improvements (continued)
  • Improvement: Combination of all technical and administrative measures as well as management measures to increase the functional reliability of a unit under consideration without changing the function required by it (continued)
  • Functionality : ability of a unit under consideration to fulfill a function based on its condition
  • Failure : Termination of the ability of a unit under consideration to fulfill a required function
  • Weak point analysis: The detection of increased wear and tear on an observation unit, which can lead to an early failure. Whereby the weak point only becomes a weak point when the elimination of the weak point is technically possible and economically justifiable.

Terms from the earlier version of DIN 31051: 1985-01, which are no longer included in the new version from 2003:

  • Damage : Condition of a unit under consideration after falling below a certain (to be determined) limit value of the wear reserve, which causes an impermissible impairment of functionality with regard to use
  • Disturbance : Unintentional interruption (or already impairment) of the functional fulfillment of a unit under consideration
  • Maintenance protection : All activities carried out before the actual work activity that are intended to prevent injuries to maintenance personnel or other persons, as well as the undoing of these measures

The English term maintenance, repair and overhaul , or MRO for short , has established itself internationally as a generic term in the field of maintenance.

Maintenance planning

Maintenance planning is the systematic preparation and definition of all actions that are required to protect the functionality of the production facilities of an industrial company from impairments until the end of their economic useful life or to restore them in the event of wear and tear and malfunctions (preventive maintenance). The maintenance plan is an answer to questions about when and what to do for maintenance work.

Education and training in maintenance

The classic career of a "maintenance technician" is vocational training (e.g. as a locksmith, electrical mechanic) with subsequent master craftsman training. In larger industrial companies in particular, maintenance staff are increasingly faced with management and marketing tasks. Strategic planning processes, team tasks (e.g. education, leadership) and also marketing ("sale" of the maintenance service by the management) are increasingly becoming the main areas of activity of maintenance employees. In Germany, there has been a professional academy course for service engineering since 1999 (BA) , this is carried out there as a dual course of study in cooperation with practical companies.

In Austria, the AMMT - Asset Management and Maintenance Technologies course was launched in autumn 2011 . The extra-occupational training course is aimed at specialists in maintenance and production.


  • Adolf J. Schwab : electrical energy systems. Generation, transport, transmission and distribution of electrical energy. Springer, Berlin a. a. 2006, ISBN 3-540-29664-6
  • Alexander Stuber, Andreas Dankl (ed.): Asset Manager 2010. Industrial maintenance. Technical building management. Market study and manual. TOP, ROOF. Behrend Trade Press Agency, Horn 2010, ISBN 978-3-9523151-3-2
  • Uwe Schönfelder: Determination of the condition of real estate using the ERAB method - basics for maintenance strategies . Werner Verlag, Dortmund 2012; ISBN 978-3-8041-5253-3
  • Matthias Strunz: Maintenance. Basics strategies workshops. Springer Vieweg, Berlin 2012, ISBN 978-3-642-27389-6

Web links

Wiktionary: Maintenance  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. DIN-TERMinologieportal, available at: or
  2. DIN 31051: 2019-06, foreword:
  3. DIN EN 13306: 2018-02, introduction:
  4. DIN 31051: 2019-06, foreword:
  5. Lünendonk List 2017: Leading industrial service companies in Germany
  6. ^ Maintenance, Repair and Overhaul (MRO) . ( Memento from December 20, 2016 in the Internet Archive ) Lexicon on the VerkehrsRundschau website , accessed on December 4, 2016