What is mean time to repair (MTTR)?

MTTR includes the time from when the failure occurs to when the system or equipment is fully functional again. Which includes the time it takes to detect the failure, diagnose the issue and fix the problem. MTTR is an important metric to monitor because it evaluates the availability and reliability of systems and equipment, the severity of incidents, and the efficacy of repair efforts. A high MTTR can result in significant unplanned downtime. By tracking MTTR, organizations can identify areas where they need to improve their processes, identify trends in failures and make decisions about how to optimize their maintenance strategies.

MTTR is often used in tandem with mean time between failure (MTBF): The average amount of time that a system or component will operate before it fails. It is a related metric that can help identify potential areas for improvement in system reliability. MTBF is sometimes represented as MTTF (mean time to failure).

MTTR is also used alongside failure rate, a measurement of the number of failures over a period of time. A failure rate does not correlate with uptime or availability for operation — it only reflects the rate of failure.

Mean time to repair (MTTR) is calculated by taking the total repair time resulting from a particular failure and dividing it by the total number of repairs that are performed during a specific period. The MTTR formula is:

MTTR = Total time spent on repairs / Number of repairs

To get an accurate measurement of MTTR, it's important to track the amount of time it takes to detect the failure. And the time spent diagnosing the issue and the time it takes to repair the problem. This can help organizations identify areas where they need to improve their processes and reduce the time it takes to repair equipment or systems, ultimately increasing their availability and reliability.

Let's say a company's manufacturing line experienced mechanical failures that resulted in three hours of repair time before the issue was resolved. During the same month, there was a total of two repairs made to the equipment due to various issues.

To calculate the MTTR for the manufacturing line during that month, we would use the formula:

Since MTTR means “total time spent on repairs” divided by “number of repairs.”

MTTR = 3 hours / 2 repairs

MTTR = 1.5 hours

So, the MTTR for that month for the manufacturing line would be 3 hours. By tracking MTTR across normal operations, the company can identify trends, improve their repair processes and reduce downtime, ultimately improving their bottom line.

Maintenance managers use an array of formulae to understand the status of their operations. They increasingly use Computerized Maintenance Management Systems (CMMS) to more readily and frequently derive such information.

Fault tree analysis (FTA) is a method for analyzing the causes of system failures by constructing a graphical representation of the fault paths that can lead to a failure event. It is often used to identify critical failure modes and develop strategies for reducing MTTR.

Root cause analysis (RCA) is a structured method for identifying the underlying causes of a problem or failure. It involves investigating the symptoms, identifying the immediate causes and tracing them back to the root cause.

Failure modes and effects analysis (FMEA) is a structured approach for identifying and evaluating potential failure modes. It involves analyzing the potential consequences of each failure mode and developing strategies to prevent or mitigate them.

Mean time to repair (MTTR) is a critical key performance indicator (KPI) that can offer several benefits to organizations, including:

• Minimizing downtime: MTTR can help organizations minimize downtime by identifying areas for improvement in the repair process. By tracking MTTR over time, organizations can identify patterns and trends in repair times and take steps to improve system availability.

• Improving system reliability: MTTR can help organizations identify components or systems that are prone to failure and take steps to improve their reliability and maintainability. By reducing the number of incidents in a given period, organizations can spend less time repairing and increase system uptime.

• Reducing repair costs: By tracking MTTR and identifying areas for improvement, organizations can reduce repair costs by improving the efficiency of the repair process. This can include streamlining repair procedures, training technicians on new technologies and reducing the need for costly emergency repairs.

• Enhancing customer satisfaction: By reducing downtime and improving system reliability, organizations can enhance customer satisfaction. This can lead to increased customer loyalty, repeat business and positive word-of-mouth referrals.

• Supporting data-driven decision making: MTTR provides organizations with a data-driven metric to track the efficiency of their repair processes. This data can be used to identify areas for improvement, make data-driven decisions about equipment maintenance and replacement and measure the effectiveness of process improvements over time.

Calculating MTTR can be challenging due to several factors, including:

• Defining what constitutes a "repair": Should the clock start when a technician first begins work on the system, or when they have identified the problem and are ready to start repairs? Determining the starting and ending points of the MTTR calculation can impact the accuracy of the metric. Accurate documentation of repair times is also essential for calculating MTTR, but incomplete or inaccurate documentation can make it challenging to establish reliable metrics.

• Limited data availability: In some cases, there may be limited data available to calculate MTTR accurately. For instance, if a system or component rarely fails, there may not be enough data points to calculate an average repair time.

• Varying repair times: The time required to repair a system or component can vary depending on the nature and severity of the problem. For example, a minor issue may be resolved quickly, while a more complex problem may require significant investigation and troubleshooting, which can significantly increase the repair time. In some industries, there may not be standardized processes for repairing equipment or addressing issues. This can make it difficult to establish consistent repair times across different systems or components.

• Unplanned downtime: Unplanned downtime can make it challenging to calculate MTTR accurately. If a system or component fails unexpectedly, there may be delays in identifying the problem and scheduling repairs, which can extend the time to repair and increase the MTTR.

MTTR calculations require accurate data collection, clear definitions and standardized processes to overcome these challenges and produce reliable metrics.

Improving mean time to repair (MTTR) requires a systematic approach to identifying and addressing the root causes of failures and reducing the total time required to repair them. Here are some steps organizations can take to improve MTTR:

• Standardize repair processes: Establishing standardized repair procedures can help ensure that repairs are performed consistently and efficiently. This can include documenting procedures, establishing checklists and providing training to technicians.

• Improve troubleshooting procedures: Effective troubleshooting can help identify the root cause of a problem quickly, reducing the time required to repair it. Providing technicians with digital tools and techniques for troubleshooting can help reduce the time frame required to identify the problem.

• Improve access to spare parts: Ensuring that spare parts are readily available can reduce the time required to repair a system or component. This can include maintaining an inventory of commonly used parts, establishing relationships with suppliers and implementing a system for tracking parts usage and replenishment.

• Use predictive and preventative maintenance techniques: Maintenance programs, including such techniques as vibration analysis and oil analysis, can help identify potential problems before they result in unplanned maintenance tasks. Alert systems can help spot anomalies before they turn into incidents.

• Implement a computerized maintenance management system (CMMS): A CMMS can help organizations track maintenance team schedules, work orders and repair history, making it easier to identify areas for improvement and measure the effectiveness of process improvements over time.

• Conduct root cause analysis (RCA): Conducting RCA can help identify the underlying causes of failures and develop strategies for preventing them. By addressing the root cause of a problem, organizations can reduce the likelihood of future failures, establish benchmarks and improve MTTR.

• Continuously monitor and measure MTTR: Continuously monitoring and measuring MTTR can help organizations establish baselines, identify areas for improvement and track progress over time. This data can be used to develop targets for improvement and measure the effectiveness of process improvements over time.

Mean time to repair (MTTR) is a critical metric that is used by many organizations across a wide range of industries. Some common use cases for MTTR include: