What is MTFB and MTTR?

MTBF (Mean Time Between Failures) and MTTR (Mean Time To Repair) are both significant manufacturing metrics for determining the availability of a machine or piece of equipment. However, there are differences between the two and how they can provide indicators for the efficiencies of processes in your business.

What is MTFB?

Mean time between failures (MTFB) is used to predict the time between failures of machinery and equipment during their normal hours of operation. The time between is represented in hours and will show how long something operates without downtime. MTFB is used only when it concerns items which can be repaired so helps plan for the time it needs to be repaired.

Before calculating MTFB, it’s important to know how reliability and availability are affected

• Reliability is how an asset performs required functions under certain conditions for a planned amount of time.
• Availability is how long something is operational and accessible for.

MTFB measures a system’s reliability and the higher the MFTB, the more reliable it is.

The equation for this is Reliability = e(time/MTFB).

Calculating MTFB

MTFB is calculated by taking how long an asset is running for and dividing it by how many breakdowns happened in the same period of time.

What a typical MTBF calculation may look like:

• Finding total uptime: Add up your total amount of widgets and how long they were tested for. For example, 50 widgets tested for 500 hours = (50 x 500 = 25,000).
• Identify total number of failures: Work out how many times there were failures for the entire number of widgets tested. For example, there may have been 30 widget failures.
• Calculate MTFB: We now know testing was carried out for 25,000 hours 30 widget failures so we can calculate MTFB: 25,000 hours / 30 failures = 833 hours

This calculation tells us that if you run a group of widgets, the average time between failures is 833 hours. It shows that MTFB isn’t predicting downtime for one component, but multiple ones.

What is MTTR?

Mean time to repair (MTTR) is the metric used to measure how long, on average, it takes to repair equipment or machinery when it’s failed. It shows how quick a business is to respond to unplanned downtime and repair assets and calculates the time from when downtime happens to when an asset is back in production.

Calculating MTTR

To calculate MTTR you need to divide the total amount of unplanned maintenance time for an asset by how many failures it experienced during the same time period. Mean time to repair is usually illustrated in hours.

The calculation for MTTR assumes:

• Tasks are carried out continuously
• They are performed by trained technicians

To calculate: MTTR = Total maintenance time / number of repairs

For example, spending 60 hours on unplanned maintenance for an asset that’s broken down 5 times during the year shows the mean time to repair is 12 hours.

How do businesses use MTTR?

The metric is used as the baseline for a business to increase their efficiency, recognise ways it can reduce unplanned downtime and positively affect the bottom line. As longer repair times for important equipment can mean products are scrapped and work orders can be missed, MTTR helps identify why maintenance might take longer than they’d like and helps make more insightful decisions to fix root causes.

For manufacturing businesses MTTR analysis offers insight into how your maintenance operations schedules maintenance, completes tasks and makes buying decisions. It will ultimately aid businesses to minimise inefficiencies which cause losses in production and money.

MTFB and MTTR are both critical metrics for manufacturing businesses. With all your data in one place, finding out the MTFB and MTTR is easy with OpsBase, sign up with us for your demo and free trial today.