Why You should measure Machine Reliability. MTBF-MTTR

What is Machine reliability

?Machine reliability is an extension of the engineering and quality functions of a manufacturer, reliability engineering is a science in itself involving stress testing, optimization analysis, probability analysis.

What is MTBF &MTTR?

MTBF is the mean time between failures, the average time the asset breaks down.

MTTR is the time it takes to repair each failure, the average time it takes to repair a failure,

The benefits of measuring MTBF & MTTR

1) When is the machine likely to fail?

2) How long does it take to fix a failure?

3) How many failures do we have in total?

4) How many breakdowns are we taking up space in the system?

5) What is the average time it takes to fix a failure?

The formula of MTBF & MTTR

MTBF - Total time Period – Downtime / number of failures

Example 480min – 160 min = 320min / 3 failures

MTBF = 106 min

You can also Translate MTBF into a failure rate

Failure rate = 1/MTBF

FR = 1/106 = 0.0094....0.94% chance that the machine will fail on a single day.

MTTR - Total of repair times /total of failures

Example 106 min/3

MTTR 35.3 min

Now we have the data to complete the availability

MTBF/(MTBF+MTTR)

106/(106+35.3) = Availability 75

Let’s look at what you now know

The machines availability is 75%......25%missing.

Let's look at the facts, this is what you now know.

The machine had 3 failures

The failures were all within 480 min

The mean time to repair took 35.3 min

The Mean time between failures was 106 min

The machine has a Failure rate of 94%.

The machine Availability is 75%

Summary

Once you have the formulas you can easily set this up on an excel and add it to your current KPI, extracting the information from the areas will take some thought but it can be done. Understanding how long repairs take gives great insight and the frequency of stops can be related to product quality in particular one-piece flow processes such as bakeries. With these calculations you actually have the starting point of a Preventative maintenance system, you can start adding Standard error mean into the excel sheet. You have also established targets such as improve repair time, reduce the number of stops, reduce the failure rate, all this can form part of an engineering Key performance indicator.

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