What is the key difference between MTTR and MTBF?

People ask the difference between a leader and a boss. The leader leads, the boss drives: Theodore Roosevelt

Introduction

Many years back I was watching an advertisement for a Car. In that, on a lonely highway, a car was under breakdown and the car owner (thief!) was seeking help from the passerby. One passerby thought of stopping their car and helping the other person. As soon as they were on the verge of stopping their car, they again speeded up their car and went away. The reason why they did not stop was that they observed that it was a ‘Toyota’ make car and how can a ‘Toyota’ breakdown on the road!       

Objective

MTTR and MTBF are two powerful performance indicators that should be used to expand the company’s knowledge about processes and reduce losses in productivity or quality of the products offered.

By understanding the key differences between these two metrics, the organization can understand how to improve the efficiency of the processes in your company.

Definitions

Total productive maintenance: A system of maintaining and improving the integrity of production and quality systems through machines, equipment, processes, and employees that add value to the organization.

Detailed Information

MTBF (Mean Time Between Failures) and MTTR (Mean Time To Repair) are two very important indicators when it comes to the availability of an equipment/asset.  

MTTR: It is the average time between the repair when equipment is under breakdown.

MTTR (repair) = total time spent repairing / # of repairs

For example: let’s say three injection moulding machines were under breakdown, two of which took 15 minutes to repair and the third one took 30 minutes. So:

MTTR = (15 + 15 + 30) / 3 = 20 minutes

MTBF: It is the average time between the failure which can be repaired.

MTBF = total lifespan across devices / # of failures

The total lifespan does not include the time it takes to repair the device after a failure. 

For example: let’s say an injection moulding machine is planned to run for 400 minutes every day for the next 25 days (10000 minutes). There was 4 breakdown in next 25 days (10000 minutes). So:

MTBF = 10000 / 4 = 2500 minutes

Following are some of the key Difference between MTTR and MTBF:

S.No. MTTR MTBF
1 It should be as low as possible It should be as high as possible
2 It measures the efficiency of the repair It measures the Reliability of an equipment
3 How much time taken to repair an equipment The difference between 2 failures of the equipment
4 Reflects the competence of the operator Reflects the effectiveness of the maintenance process
5 Availability of relevant critical spare parts for maintenance and the effectiveness of the preventive maintenance   Availability of desired quality of the spare parts used for maintenance
6 Reflects the turnaround time Indicator of the Expected Performance
7 Helps the organization to identify the equipments which are taking more time to repair Helps the organization to identify the equipments which are repeatedly under breakdown
8 The objective is to save money on the bottom line The objective is to reduce the breakdown
9 Helps to address why critical equipment are taking more than the normal time for repair Helps to understand which equipments are under breakdown more frequently
10 Helpful for taking a decision whether to replace equipment or continue with the repair Essential tool during the design and production stages of many products
11 Helps to predict lifecycle costs of new equipment or systems Helps to predict the requirement of replacement parts

Present Challenges

  • How often MTTR and MTBF are considered key indicators in the organization?
  • How often the data is authentic while calculating MTTR and MTBF?
  • How often top management dig deep into this data to analyze the real issues?

 

References:

IATF 16949: 2016

Industry Experts

 

This is the 117th article of this Quality Management series. Every weekend, you will find useful information that will make your Management System journey Productive. Please share it with your colleagues too.

Your genuine feedback and response are extremely valuable. Please suggest topics for the coming weeks.

 

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Rajiv Juneja
Rajiv Juneja
11 months ago

Nicely explained MTTR and MTBF in simple language with easy example

WilliamMap
8 months ago

Great post. I used to be checking continuously this blog and I’m impressed! Extremely helpful info specially the final part 🙂 I handle such information a lot. I used to be seeking this particular information for a very long time. Thanks and good luck.