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What is the MTTR and the MTBF?
Learn about the key performance indicators for a first-class maintenance and how you can calculate them with maintenance management software.
Mean Time to Repair (MTTR)
The Mean Time To Repair (MTTR) is the average time taken to repair an asset and one of the most common metrics used by maintenance managers. As the name suggests, the MTTR represents the average time is necessary to perform troubleshooting and repair a piece of equipment where a failure occurred, returning it to its initial operating conditions. The maintenance time of an asset starts when the incident occurs and ends when the equipment resumes its normal operation.
This metric is a critical indicator of how an organization can respond to a problem and solve it efficiently.
How to calculate the MTTR?
The MTTR is the result of the total corrective maintenance time divided by the number of maintenance actions over a given period of time. It is calculated using the following formula:
From this formula we can quickly understand that the MTTR is determined by two variables: the total corrective maintenance time (which means - the total time spent repairing the equipment) and the number of repair actions. To reduce the MTTR, you have to be aware and try to reduce both these factors.
How to calculate the MTTR using maintenance software (CMMS)?
The maintenance software will record the date and time when a piece of equipment is reported as inactive for repair purposes in its database. The maintenance solution calculates the time taken to repair the asset until it returns to its normal operating condition. Then, you can access MTTR reports and track its evolution over time. You can achieve a more accurate MTTR calculation by splitting the downtime into its component parts - the time spent waiting for the technician, for the delivery of the required part, the duration of the repair, etc.
Mean Time Between Failures (MTBF)
TBF is the acronym of Mean Time Between Failures, which represents the average time passed between equipment failures. This is an important metric that indicates a period of time during which the unavailability of the asset must be managed.
In other words, the MTBF is the average time that the equipment works correctly between failures. The MTBF is a very important performance indicator for the most critical assets.
This metric does not provide for any scheduled maintenance operations such as inspections, recalibrations or preventive part replacements.
While the MTTR only influences asset availability, the MTBF affects both availability and reliability.
How to calculate the MTBF?
The different factors influencing MTBF are mainly human. For example - was the machine installed correctly? Was the equipment properly designed and built? Have the previous maintenance operations performed by technicians contributed to this failure?
The formula for calculating the MTBF is:
How to calculate the MTBF using the Valuekeep maintenance software?
The maintenance management solution has built-in MTBF reports and therefore, it is easy to directly analyze the data regarding this metric for any asset. When a piece of equipment is unavailable due to repair, you need to select the reason/incident that describes this situation. The possible reasons for classifying an asset as unavailable can be specified in the maintenance software settings. Once the equipment is repaired and able to resume operation, you can set this asset as available.
This information on the availability/unavailability states of assets is used to calculate the MTBF and, for that reason, must always be up to date.
Why are the MTTR and MTBF useful and important metrics?
Based on the MTBF, maintenance managers can understand which pieces of equipment are most prone to faults - which indicates that these assets may need more maintenance or even replacement.
As for the MTTR, the goal should be to reduce it. Reducing the MTTR depends on, on the one hand, performing preventive maintenance to achieve a lower number of faults and, on the other, reducing the time spent in repairs. The goal here is to act quickly and to prepare the technical team because the sooner they respond to an incident, the faster the fault will be fixed.
While the MTBF measures reliability, the MTTR is a strong indicator of the effectiveness of repairs. Together, these two metrics provide an estimate of how long a particular asset or location was unavailable. Analyzing the MTBF and the MTTR together also provides an opportunity to calculate estimates regarding production decreases or even interruptions during failures. The MTBF and the MTTR also allow for retrieving indicators on maintenance costs over a given period of time.