If your first question in our exploration is “What does MTBF stand for?” the answer is “mean time between failure.” But what is mean time between failure?
To answer the question “What is MTBF?” we outline a brief definition of mean time between failure as follows: it is a quantitative and maintenance metric that measures the average operating time (expressed in hours) between the failure rate of a given asset or system within a manufacturing or industrial environment. It is used to measure the performance, safety and equipment design of complex or simple machines.
In this MTBF definition, it is also important to emphasise that the MTBF formula focuses on unplanned maintenance only. It, therefore, does not take into account scheduled maintenance or planned maintenance, which may include aspects such as inspections, recalibrations or preventive part replacements.
Mean Time Between Failure Calculation
An MTBF calculation requires using a specific mean time between failures (MTBF) formula. While the MTBF equation is quite straightforward, it should be noted that there is no industry average that serves as a benchmark for what a good MTBF score is.
This is because every industrial or manufacturing organisation deals with different types of equipment with differing warranties and lifespans. This means that each piece of equipment’s longevity will depend on numerous factors that cannot be collated into an average that the industry can use.
However, as a rule of thumb, the higher the MTBF value is in terms of hours, the better the performance of the piece of machinery in question due to longer operation time. Below, we outline the mean time between failure formula to help you calculate MTBF accurately.
MTBF = Total time in terms of the number of operational hours ÷ Total number of breakdowns or failures
Here is an MTBF formula with an example:
In terms of the total number of operational hours, say that there are eight productive hours per day for the machine in question. There are five days in a working week when this machine is productive. In addition, there are 52 weeks in a given year. This means that 8 x 5 = 40 and 40 x 52 = 2,080.
As such, there are a total of 2,080 hours in a year when the machine should ideally be working. However, if there are, say, five failures during the year, we would divide 2,080 by 5 to get 416 hours. This is the MTBF. It essentially means that the machine will, on average, operate for 416 hours before its next failure or breakdown. This can help reliability engineers carry out a stronger root cause analysis of productivity and improve total uptime as the maintainability of assets becomes more predictable.