MTTR can cause reliability problems if not used right

The use of mean time to repair (MTTR) to improve reliability can cause problems if it’s used alone, in immature organizations, or if it’s used without an understanding of the potential problems it can use.


Metrics, also called key performance indicators (KPI), are a force for good when used at the right time and with the right complementary or supporting elements. When they are used at the wrong time, however, they can have unintentional consequences or drive the wrong behaviors. In particular, the use of mean time to repair (MTTR) to improve reliability can cause problems if it's used alone, in immature organizations, or if it's used without an understanding of the potential problems it can use.

This metric can drive an organization in the opposite direction of the world-class performance that may have been intended. If the organization is immature from a reliability standpoint and chooses MTTR as the focus, then the company is setting itself to become very reactive by very quick to respond to failures. The problems with that include:

  • Reactive response is at least five times more expensive than planned and scheduled work.
  • Operations will demand faster response time to lower MTTR.
  • Rushed repairs are less reliable.
  • Reactive response requires more expensive spare parts stocking.
  • Companies will have skilled maintenance technicians just standing on the manufacturing floor doing nothing and waiting for a failure to occur.
  • Pressure to make the repair as quickly as possible can lead to taking elevated safety risks.

Many sites that choose MTTR as a primary metric early in their reliability journey create a brigade of firefighters at the ready with crash carts and mounds of spare parts. In general, though, companies want to prevent the failures from happening at all or at least reduce the frequency. Metrics such as mean time between failures (MTBF) might be a better option early on in the process and then use MTTR after the reliability has been increased. Using MTTR later allows companies to address issues that can't be prevented and help managers understand training gaps and other issues that might be affecting repair times.

Shon Isenhour, principal at Eduditio, LLC.If MTTR is the only metric being used, then companies will create tools like crash carts and quick response teams (QRT) instead of using tools such as root cause analysis (RCA) to understand and eliminate the reoccurring problem. If your metrics are driving the wrong behaviors, then it might be time to do a reassessment.

What metrics have worked for your company? Let us know in the comments section below.

- Shon Isenhour is a founding partner at Eruditio and is a part of Plant Engineering's editorial advisory board. This article originally appeared on Eruditio's blog. Eruditio is a CFE Media content partner. Edited by Chris Vavra, production editor, CFE Media,

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