What is MTBF? (Mean Time Between Failures) What is Mean Time Between Failure?

 The Mean Time Between Failure (MTBF) is a measurement of how long equipment lasts between breakdowns or stops working. MTBF (mean time between failures) is a metric that helps organisations understand how long their equipment will last (and if they have a problem with reliability).

How is MTBF used?

The Mean Time Between Failure (MTBF) is a maintenance metric that estimates how long equipment can work without being disrupted. This logically corresponds to the equipment's availability. One of the most important indications of overall equipment performance is availability, also known as uptime, which is always a priority area for increasing productivity. The MTBF and another statistic, the MTTR, can be used to calculate an equipment's total uptime (mean time to repair).

It's vital to remember that MTBF only applies to repairable objects. It can be used to plan for scenarios that need the repair of critical equipment in manufacturing operations. Knowing this information allows you to make informed decisions for the plant.

MTBF vs MTTF

The Mean Time to Failure is another measure that links time to failure (MTTF). MTTF, like MTBF, is a time measurement. It calculates the amount of time until a piece of equipment completely fails. The sole distinction between MTTF and MTBF is that MTTF is only applicable to non-repairable objects. The presumption is that once the MTTF is reached, the item's maximum hours of service have been reached.

How Do You Calculate MTBF?

The MTBF is calculated by taking the total time a piece of equipment is running (i.e. uptime) and dividing it by the number of breakdowns that occurred over the same period.

MTBF = Total uptime / # of breakdowns

Mean Time Between Failure (MTBF) Example

Take for example a mechanical mixer designed to operate for 10 hours per day. Suppose the mixer breaks down after normally operating for 5 days. The MTBF for this case is 50 hours as calculated below.

MTBF = (10 hours per day * 5 days) / 1 breakdown = 50 hours

The MTBF calculation will require more steps when accounting for longer periods of time with increased occurrences of breakdowns.

Let's imagine a mechanical mixer that runs for 10 hours each day breaks down twice in a 10-day period. The first failure happened 25 hours after the start time and required 3 hours to repair. The second breakdown occurred 50 hours after the mixer was turned on, and it took 4 hours to get it back up and running.

The succession of events is illustrated by the timeline below:

We can more readily account for the machine's entire operational time using the timeline. The overall uptime period for the provided example is the sum of 25, 22, and 46 hours.

The MTBF formula is used to calculate the total uptime and number of breakdowns (or failures) given the total uptime and number of breakdowns (or failures):

MTBF = (25 hours + 22 hours + 46 hours) / 2 breakdowns = 93 hours / 2 breakdowns = 46.5 hours

How to improve MTBF

Equipment uptime is increased by increasing the MTBF. The maintenance crew may schedule maintenance tasks more efficiently by keeping track of the MTBF for each piece of equipment, especially those that require continuous operation.

To improve MTBF, the first step is to ensure that the data being collected is accurate. Tools like varied maintenance software are being developed to ensure that data is recorded correctly and accurately.

The next stage in data collection is to use it to undertake proactive preventative maintenance. Maintenance checks and operations such as checking for adequate lubrication, aligning calibrating systems, and cleaning pay off by lowering the number of major stoppages due to breakdowns.

How to Relate MTBF to System Availability

As previously mentioned, availability metrics are expressed in terms of MTBF and MTTR. Think of it as calculating the availability based on the actual time that the machine is operating—excluding the time it takes for the machine to recover from breakdowns.

This is quantified by the following equation:

Availability = MTBF / (MTBF + MTTR)

Availability is one of the three factors contributing to the overall equipment effectiveness of a plant. The above equation signifies the relationship of improving the MTBF and other metrics related to improving the plant’s performance.