MTTR ( Mean Time to Repair ) indicator, which is the average time from the moment of failure to repair the damaged device. This indicator is used as one of the key performance indicators by Maintenance departments in enterprises. Examples of using the MTTR indicator:

Example: There were 4 failures in the company, the first lasted 2 hours, the second lasted 3 hours, the third 2 hours and the fourth lasted 4 hours. So MTTR will be:


MTTR =(2+4+2+4)/4= 3 h


MTTF ( Mean Time to Failure ) is another of the key performance indicators. This indicator is calculated from the beginning of the device's operation or from its last repair until the next failure. Below is an example for calculating the MTTF indicator:

Example: One of the machines operated for 300 hours, had one 10-hour inspection and had 4 failures lasting: 2, 4, 2, 4 hours. MTTF will be:


MTTF =((300-10)-(2+4+2+4))/(4+1)=278/5=55,6


The last indicator quoted in this article is MTBF ( Mean Time Between Failure ), which is the average time between failures. The actions of enterprises always strive to reduce failures to a minimum, and thus to the highest value of MTBF. This indicator is treated as the sum of the above-mentioned indicators, i.e. the formula for MTBF is: