The key area of technical supply management work at a company is the
maintenance service. Maintenance service for business has an important
meaning, mainly for preparing and maintaining the technical condition of the machine parks as well as for efficient supply management.
Keeping the technical infrastructure at adequate productivity and efficiency
levels, requires the use of appropriate methods and management tools as well
as an adequate organization of the maintenance services.
Choosing the right maintenance strategy will generate multi- level gains for the
company: safe and effective development, modernized production processes,
elimination of waste and losses. The basic element of effectiveness assessment
in the case of production processes and maintenance, are various indicators
allowing to estimate the factual effectiveness, reliability and availability of the
machine park. It is rather difficult to imagine the lean management philosophy
without key performance indicators.
Find out what KPIs actually are, how to measure them, and why they are
actually worth your time.
What are: effectiveness and key performance indicators?
In order to be able to discuss key performance indicators, you first need to
define what effectiveness actually is. Effectiveness is one of many defining
indicators in the collection of objects and systems. It is usually defined as
property of the object used or of the system of objects, which defines the level
of goals reached in a certain time period.
Exploitation effectiveness is a ratio of the effects achieved in a time period, throughout the course of the objectʼs exploitation, to the reserve that caused such effect.
The effectiveness of an operating element or a collection of operating elements
is impacted by the pre operating indicators (required actions and initial
disbursals, related to the systemʼs features and environment), as well as the
operating indicators identified in the operating process (external factors) and
operating features (dependability, durability, repairability, etc.)
To assess the system effectiveness, there is a number of assessment criteria
available. Nevertheless, the most common and most favorable one is the
assessment system based on key performance indicators. These indicators can
be used on many levels of maintenance and production processes, to measure
quality of a production area, effectiveness of a production line, or of a single
machine, or a device. According to the norm: PN-EN 15341S2007, key
performance indicators are defined based on the economic, organizational and
technical criteria. Moreover, the above mentioned norm enables choosing the
right KPI. Key performance indicators are the basis for the companyʼs success.
Choosing the right KPI, its implementation and analysis will in turn impact
maintenance and the final success of administered improvements within
Key performance indicators: MTBF, MTTR, MTTF, OEE, their features and measurement methods
During the process of obtaining specific for the maintenance indicators, the
norm: PN-EN 15341S2007 suggests two approaches. The first one is choosing
the indicators from the list of available markers and analyzing them on the basis
of requirements and the production process specification. The second
approach focuses on the assessment of different machine maintenance
processes, through the functional analysis. The indicators recommended by the
norm are as follows: the MTBF indicator, the MTTR indicator, the MTTF indicator and the OEE indicator.
The MTBF indicator: Mean Time Between Failures and failure frequency
The MTBF indicator is one of the basic indicators defining failure frequency. It is
understood as mean work time between failures in a certain time period.
The MTBF indicator is usually expressed in minutes.
To calculate the MTBF indicator, multiply the work time and the amount of failures that had occurred in that time period. The MTBF indicator can also be estimated based on the total sum of the MTTR and the MTTF.
With the help of the MTBF indicator, we can monitor machine failure frequency as well as plan preventive actions for the key machine parts.
The MTTR indicator: Mean Time To Repair
The MTTR is an indicator describing mean time of factual repair, from the
moment of failure report to failure resolution. The MTTR is a ratio of repairs
performed to the amount of failures. In practice, we can calculate it based on
the total failure time of selected machines or the entire system, to the amount
of machine or system failures.
Example: a machine experienced two failures in a certain time period. The first
failure lasted 1 hour and the second one: 3 hours.
Calculating the MTTR indicator: (1+ 3)/2 = 2 h.
The MTTF indicator: Mean Time To Failure
The MTTF indicator defines mean work time of a device, from the beginning of
its use or from the last repair to failure. It is usually expressed in hours. The MTTF indicator is defined by multiplying the difference of machine available time and the total number of failures occurred.
The machine available time is the estimated time the machine would function,
divided by the time of planned preventive actions and maintenance.
For example: in a certain time period, a machine was functioning properly for 100
hours during which two failures had occurred. The first one lasted 1 hour and
the second one: 2 hours. Additionally, the machine underwent planned checkup
which took 2 hours.
The MTTF indicator equals 31,67 h. Why? (100 – 1 – 2 – 2)/(2 + 1)= 31,67 h.
The OEE Indicator: Overall Equipment Effectiveness
The OEE indicator identifies the percentage of manufacturing time that is
actually productive. It is one of the most important key performance indicators;
it is calculated by multiplying three other indicators: availability, performance
- availability: a ratio of the time planned for carrying out a task to the factual
time spent on that task. This indicator may be decreased by failures,
maintenance activities or machine change- overs and/or start-ups.
- performance: defined by multiplying standard time to manufacture end
product to the amount of elements produced, and than dividing it by
available employee time
- quality: quality is defined as a ratio of value or (less frequently) an amount
of quality goods manufactured and the value or (less frequently) an amount
of overall goods manufactured
The OEE indicator informs how many quality goods is a machine (or a group of
machines) capable of producing, after deductig time waste and faulty goods.
Based on international research, the following conclusions have been drawn:
world class manufacturers are able to accomplish the OEE indicator, oscillating
at the level of slightly above 85%, which consists of the following indicators:
performance: 95%, quality: 99,9%, availability: 90%
Why are key performance indicators worth estimating and monitoring?
Those companies who are measuring and estimating their KPI value on a
regular basis, in the context of production processes, may gain multi- level
benefits. That in turn translates into the overall effectiveness and accuracy of
the entire production area. Below are the greatest benefits of key performance
Verifying effectiveness of the maintenance service
MTBF, MTTF and especially the MTTR indicator are excellent key performance indicators for the maintenance service. Thanks to their measurement, it is possible to track the maintenance trends within the entire production territory, production lines and of selected machines. For instance, if the MTTR indicator decreases, it means that mean time of failure removal is shorter. When the MTTR indicator increases, mean time of failure removal is prolonged. The uncomplicated analysis of such marker allows a company to monitor the growth or the drop in effectiveness among maintenance service.
Check- up planning and preventive maintenance
Based upon defined key performance indicators, precision planning is possible for all maintenance activities in the aspect of production line, and in the case of single priority machines at a facility. For example: letʼs assume that a preventive part exchange should be conducted every 85% of the calculated MTBF
If the indicator equals 800 minutes than a preventive exchange of key parts
should take place after 680 minutes from the last failure. It is important that the
85% MTBF rule only applies to those parts which may have a significant impact
on the production process.
Measuring progress within autonomous maintenance
The basis for the TPM system is autonomous maintenance, which contributes
to improving the awareness of machine operators in terms of their technical
An increase in awareness determines rapid failure recognition and improves the
machine care, which in turn significantly increases the MTBF indicator.
In consequence, it limits the number of failures within the machine park.
Verifying the effectiveness trend of failure removal
Establishing the marker for the time period of failure removal, allows the
company to verify the effectiveness of shortened time of failure removal,
analyse the process and separate those activities that bring in value from those
In practice, based on the estimated key performance
indicators, more often than not, almost half of the total of activities within the
failure removal is waste. It could be looking for a mechanic or an operator,
complementing the tool set or obstructions on the level of communication. The
majority of waste occurring within the failure removal is typically of
Effectiveness measuring and KPI monitoring allow a company to obtain
production pillars, crucial for significant effectiveness improvement of the
maintenance service, and maximising the efficiency of the entire production
area. All the above mentioned measurement methods and KPIs can be found in
the CMMS program for management, by QRmaint.
How to track indicators?
The most popular way to track indicators in an application are the so- called
KPI dashboards- a collation of the most important key performance indicators.
Have a look at the QRmaint indicator collation: the QRmaint KPI dashboard