MTBF | Mean Time Between failure | MTTR | Mean Time To Repair

MTBF | Mean Time Between failure | MTTR | Mean Time To Repair


→ MTBF and MTTR are a very important plant indicator.
→ The MTBF is the mean time between failure and MTTR is the mean time to repair.
→ These two indicators are very useful to improve Product Quality and implementing Lean Manufacturing culture in the factory.


What is MTBF (Mean Time Between failure)?

→ Mean time between failures (MTBF) indicates the expected time between two failures for a repairable machine or system.
→ MTBF = [(Total working time) - (Total Breakdown time)] / (No of Breakdowns)
or
→ MTBF = (Total up time) / (number of breakdowns)
→ It is very important for TPM implementation which is one of the Lean Manufacturing Tool.


➤ Example of MTBF:

→ Three similar machines starting to function properly at time 0 hours are working until all of them fail.
→ The first machine failed at 120 hours, the second machine failed at 140 hours and the third machine failed at 150 hours.
→ The MTBF = (Total up time) / (number of breakdowns)
                       = [(120+140+150)]/3
                       = 136.667 hours.

→ The MTBF of the machine is the average of the three failure times, which is 136.667 hrs.

→ It can be calculated as the arithmetic mean between the failures of a machine.
→ In other words, It is the average time between the failure of a machine.
→ This value 136.667 means that a failure in the system occurs every 136.667 hours and it generates losses to the company.
→ The opportunity is to increase the time between two failure.
→ In other words, the MTBF is the time from one failure to another for a repairable machine.

➥ How to improve MTBF:

→ We can improve MTBF by regular maintenance of machines.
→ By implementing small Kaizen activity for the machine.
→ Make a machine failure history book and take a strong preventing action on it so this failure will not repeat in the future.


➤ Benefits of MTBF:

→ It is a basic indicator to predict the reliability of a machine.
→ If the MTBF has increased after a preventive maintenance activity then this indicates a clear improvement in the quality of your processes
→ The MTBF increase will show that your maintenance or verification methods are going good.
 It should be used to elaborate on the company’s knowledge about processes.
→ It reduces losses in productivity and also improves the quality of the product.


What is MTTR (Mean Time To Repair)?

→ Mean time to repair (MTTR) is the average time required to analyze and solve the problem.
 In other words, failed equipment returns to normal operating conditions.
 It is a basic technical indicator related to the maintainability of the machine and repairable parts.
→ It represents the average time required to repair a failed component or machine.
→ Maintenance time is defined as the time between the failure of the machine and the machine is returned to production
→ In other words, how long the machine is out of production.
 This includes notification time, analysis time, fixing time, waiting time, reassembly time, alignment timing, calibration time, testing time, etc.
 MTTR tells us how well an organization can respond to machine failure and repair it.
→ The formula of MTTR is explained as the total maintenance time divided by the total number of repairs over a specific period.
 MTTR = Total maintenance time / number of repairs
→ MTTR is the mean time between the machine failure and machine returns to operation
→ It is also called as the mean time to recovery.



➤ Example of MTTR:

→ A machine should operate correctly for 20 hours. During this period, 6 failures occurred. The sum of all failure time is 90 minutes.
→ The MTTR = Total maintenance time/number of repairs
                       = 90 / 6
                       = 15 minutes


➥ Why MTTR (Mean Time To Repair) is important?

→ It has a remarkable effect on the organization’s profit.
→ Long MTTR means loss of productivity.
→ Due to long MTTR sometimes, an organization can miss orders or it can impact on business relationships.
→ To reduce the impact of MTTR, organizations should have their own maintenance teams and hold critical spare parts onsite or run parallel production lines.

➥ How to improve MTTR:

→ We can improve MTTR by Preventive Maintenance Practise.
→ Improving MTTR means reducing the mean time of repairing for critical machines.
→ By Preventive Maintenance, the failure rate of the machine decreases and efficiency increases.
→ We can add regular checks during machine startup, so the problems can be identified early before they become something wrong and hence MTTR will reduce.
→ Make a standardize procedure for regular check and implement.


➤ Benefits of MTTR:

→ It indicates the efficiency and productivity of a machine.
→ MTTR has reduced after preventative maintenance of the machine.
→ By reducing Mean Time To Repair we can improve the efficiency and productivity of the machine.
→ Lower Mean Time To Repair (MTTR) indicates that your company has an immediate action plan to overcome machine failure.
 It should be used to elaborate on the company’s knowledge about how strong the action plan against the machine failure.
→ It reduces losses in profit and also improves productivity and Quality of the Product.


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