What is mean time to repair (MTTR)?

MTTR stands for mean time to repair and is a key maintenance metric that indicates the average time taken to diagnose and rectify faulty equipment. It essentially measures an organization's efficiency in handling and resolving unplanned equipment breakdowns.

The MTTR encompasses the following steps:

  1. Alerting the technicians about the issue.
  2. Diagnosing the root cause of the problem.
  3. Undertaking necessary repairs.
  4. Giving the equipment time to cool down, if necessary.
  5. Reassembling, aligning, and calibrating the equipment.
  6. Finally, setting up, testing, and restarting the equipment for regular production.

Notably, MTTR does not factor in the waiting period for replacement parts.

How to calculate MTTR

The MTTR formula is calculated by dividing the total unplanned maintenance (opens in new tab) time spent on an asset by the total number of failures that asset experienced over a specific period. Mean time to repair is most commonly represented in hours.

The MTTR calculation (opens in new tab) assumes that:

  • Tasks are performed sequentially
  • Tasks are performed by appropriately trained personnel



Total maintenance time  ÷

Number of repairs

For example, if you have spent 50 hours on unplanned maintenance for an asset that has broken down eight times over the course of a year, the mean time to repair would be 6.25 hours.

What is considered a world-class MTTR is dependent on several factors, like the type of asset, its criticality (opens in new tab), and its age. However, a good rule of thumb is an MTTR of under five hours.

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How is MTTR used?

Mean time to repair is used as a baseline for increasing efficiency, finding ways to limit unplanned downtime, and boosting the bottom line. MTTR helps organizations identify why maintenance may take longer than ideal and make more informed decisions to fix the underlying causes.

Example of MTTR

Consider a beverage manufacturing plant where a crucial piece of machinery breaks down. This machine is responsible for filling bottles, and any delay in its operation directly affects the production line.

Upon breakdown, the clock starts ticking. The maintenance team is alerted, and they begin the process of diagnosing the issue. After an hour, they identify that a specific component has malfunctioned. Fortunately, they have the spare part in stock. It takes another two hours to replace the part, test the machinery, and ensure everything is working as expected. The total time taken from the machine breaking down to it becoming operational again is three hours, making the MTTR for this incident three hours.

If such breakdowns happen frequently and the MTTR remains high, the plant will consistently miss its production targets, leading to potential order delays and disgruntled customers. However, by tracking MTTR, the plant management can identify patterns. For instance, if the same component is frequently causing the issue, it might be worth investing in a higher-quality replacement or even considering redesigning that part of the machine. Over time, by addressing these root causes, the plant can effectively reduce its MTTR, ensuring smoother operations and satisfied customers.

What are some of the benefits of measuring MTTR?

Measuring mean time to repair (MTTR) offers various benefits to organizations, especially in understanding, optimizing, and improving their maintenance and repair processes. Here are some of the primary benefits:

  • Performance benchmarking: MTTR provides a standardized metric that organizations can use to benchmark their maintenance performance over time or compare against industry standards or competitors.
  • Efficiency evaluation: By monitoring MTTR, companies can gauge the efficiency of their maintenance teams and procedures. High MTTR can indicate inefficiencies or areas that need improvement.
  • Resource allocation: Understanding MTTR can help in allocating resources more effectively. If certain equipment consistently has a high MTTR, it might need more technicians or specialized tools.
  • Uptime maximization: Reducing MTTR directly correlates with increasing equipment uptime. By identifying and addressing the factors that prolong repair times, organizations can boost their operational availability.
  • Cost savings: Longer repair times often equate to higher costs, whether from labor, lost production, or other associated expenses. By striving to reduce MTTR, organizations can realize substantial cost savings.

What are some of the challenges when measuring MTTR?

Measuring mean time to repair (MTTR) provides valuable insights for organizations, but there are challenges associated with its calculation and interpretation. Here are some of the common challenges faced:

  • Varying definitions: MTTR can be defined differently across organizations. Some may start the clock when an incident is first reported, while others might begin when the technician first engages with the issue. This variance can make benchmarking and comparisons difficult.
  • Inconsistent data collection: Reliable MTTR measurements require consistent data collection methodologies. If data is collected haphazardly or if some incidents are not logged, the MTTR value can be skewed.
  • Multiple failures: If a piece of equipment experiences multiple, concurrent failures, determining a clear start and end time for each repair can be challenging. This can complicate the calculation of MTTR.

What does MTTR mean for maintenance?

Exploring MTTR offers a lens into the intricacies of your maintenance team's equipment procurement, task scheduling, and execution processes. At its core, MTTR aims to identify and eradicate bottlenecks that lead to production halts and the subsequent financial implications. Below are some important ways that MTTR directly influences maintenance teams.

Deciding between repair or replacement

MTTR serves as a pivotal tool in determining whether to repair or replace aging assets. An increasing repair duration for aging assets could be a sign that replacement is the more cost-effective approach. Furthermore, MTTR can guide procurement and design strategies by offering predictions about the lifecycle costs of emerging systems.

Optimizing preventive maintenance schedules

While MTTR primarily evaluates reactive maintenance, its insights can enhance preventive maintenance (PM) routines. If certain assets consistently have lengthy repair times, it may hint at ineffective associated PM tasks. MTTR becomes the bridge to discerning the root of such inefficiencies, laying the groundwork for solutions. As an illustration, if MTTR is on the rise, non-standardized PMs could be culprits, escalating equipment breakdowns. For instance, a work order might indicate a part needs lubrication but may omit specifying the lubricant type or quantity. Enriching work orders with these specifics can expedite tasks, cutting down on downtimes.

Streamlining MRO inventory management

An unusually protracted MTTR might signal inefficiencies in your parts strategy. Disarrayed spares and stockouts are notorious for prolonging repair times. Studies suggest (opens in new tab) that nearly half of all unexpected downtimes are attributable to inadequate spare part availability. Additionally, technicians often spend between 10% to 25% (432kb PDF, opens in new tab) of their time in the quest for elusive parts.

If particular assets or specific plant areas consistently exhibit extended MTTRs, it’s prudent to scrutinize if parts discrepancies are the culprits. Assess whether essential components are recurrently out of stock, faulty, or incorrectly labeled. Moreover, consider utilizing tools designed to precisely forecast the parts needed for imminent tasks (including unplanned ones) to avert such predicaments in the future.

Modernizing MTTR for maintenance teams

Maintenance teams can leverage modern technology in numerous ways to optimize and speed up the repair process. Here are some strategies and tools that can be used:

  • Computerized maintenance management systems (CMMS): This software assists maintenance teams in tracking work orders, spare parts inventory, and preventive maintenance schedules. Immediate access to this data can speed up decision-making and the repair process.
  • Predictive maintenance (PdM): Leveraging sensors and analytics, predictive maintenance forecasts when equipment will fail, allowing teams to address potential issues before they become severe. This can reduce repair time by preventing unexpected breakdowns.
  • Augmented reality (AR): AR glasses or devices can overlay digital information on the real world, guiding technicians through repair processes, helping them identify components, and providing real-time diagnostic data.
  • Machine learning and AI: Advanced algorithms can analyze vast amounts of data to find patterns that might be missed by human analysis, helping in the early detection of problems.
  • Drones: For large equipment or installations, drones can quickly perform visual inspections, identifying potential issues without the need for human intervention.
  • Wearable tech: Devices like smartwatches can help technicians keep track of tasks, receive notifications, and even measure biometrics to ensure they aren't overly fatigued.

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Your business and MTTR

The mean time to repair serves as a barometer for gauging the efficacy of an establishment's maintenance protocols and methodologies. Beyond that, it sheds light on the worth and functionality of assets, empowering organizations to make informed decisions regarding asset stewardship. By leveraging MTTR as a foundation, companies can streamline operations, clear obstacles, and dispel ambiguities in their maintenance routines. This, in turn, ensures minimal disruptions, allowing businesses to refocus on their core competencies: producing and marketing their products.

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