How Failure Metrics Improve your Maintenance and Reliability Program
Maintenance and reliability organizations are defined by the reliability of their assets, and every plant’s goal should be minimizing equipment downtime. Asset failure has a direct effect on the company’s bottom line, as unexpected maintenance can cause production delays and unplanned expenses.
Mean Time to Repair (MTTR) is a maintenance metric that helps teams understand how efficiently they resolve unplanned maintenance issues, as well as identify and resolve bottlenecks in their processes. Reducing MTTR is key to improving a plant’s efficiency. A computerized maintenance management system (CMMS) software can help track MTTR and other common maintenance key performance indicators.
What is Mean Time to Repair (MTTR)?
MTTR calculates the average time it takes to repair a specific asset and bring it back into operation after an unexpected breakdown. Usually expressed in hours, MTTR refers to the average length of time between an asset’s failure and its return to normal operation.
How to Calculate MTTR
Finding the MTTR is a fairly simple process, but it requires some knowledge about an asset’s performance history, including the total amount of time spent on unplanned maintenance tasks as well as the number of incidents the machine has experienced during a given period of time.
An effective MTTR calculation measures the total amount of time it takes to for the team to identify a problem, diagnose the issue, complete the repair, reassemble and calibrate the asset, and finally restart and test the equipment.
To calculate MTTR, divide the total number of hours an asset is offline for unplanned maintenance — from the moment of failure until the asset is completely restored — by the total number of repairs done during a predetermined period of time. This calculation can be expressed with a simple formula:
Total Maintenance Downtime ÷ Number of Repairs = MTTR
A low MTTR means that the asset can be easily repaired and promptly returned to service, resulting in little if any effect on operations. Meanwhile, a higher MTTR score indicates a major impact, usually resulting in costly downtime of one or more systems.
Maintenance and reliability experts agree that an ideal MTTR is around five hours, but this varies by asset type. The end goal is to find and reduce high MTTR scores and improve the efficiency of repairs.
Why is MTTR Important?
MTTR is a valuable metric to help you maximize the efficiency of your maintenance operations. MTTR helps answer questions like:
Should an asset be repaired or replaced?
If the average repair process takes an exorbitant amount of time, it may be easier and more cost-effective to replace the asset instead.
When should preventive maintenance be performed?
MTTR can provide insight into the optimal timing for preventive maintenance to maximize an asset’s lifespan and avoid unexpected failures.
What is slowing down repair times?
MTTR can help you identify and resolve bottlenecks in your maintenance operations. For example, a disorganized parts inventory management process can significantly increase the time it takes to get a machine back up and running.
How to Improve MTTR
Reducing MTTR requires deep analysis of failures, close monitoring of asset condition, and a planned schedule of preventive maintenance tasks.
Condition Monitoring
As Internet of Things (IoT) technology has evolved and become more accessible, many manufacturing plants have begun to adopt condition monitoring programs to both monitor equipment condition in real time and track asset performance over time. Smart sensors continuously monitor conditions like temperature and vibration that are often the first indication of machine failure.
Condition monitoring provides valuable insight into baseline system performance and can alert maintenance staff when conditions exceed a predefined threshold for normal/optimal operation. This allows maintenance personnel to address and repair smaller issues (for example, replacing a worn bearing) before it leads to failure and unplanned downtime. By enabling minor maintenance problems to be resolved before they escalate to total failure, condition monitoring can significantly reduce an asset’s MTTR.
Predictive Maintenance
The insights gained from condition monitoring unlock the ability to perform predictive maintenance on your equipment. Predictive maintenance is different from scheduled preventative maintenance because it uses data from your machines themselves to predict when failures may occur and help prevent them from happening in the first place. These data-driven insights allow you to continuously improve your MTTR scores, ultimately time and costs while maximizing production uptime.
What is the Difference between MTTR, MTBF, and MTTF?
MTTR is just one measure of asset performance. Other performance metrics include Mean Time Between Failures (MTBF), which indicates an asset’s overall reliability by measuring the average amount of time between incidents; and Mean Time to Failure (MTTF) which is used to determine the average lifespan of assets that cannot be repaired.
Together, these maintenance KPIs help you determine the overall effectiveness of your maintenance team when responding to equipment performance issues. Use MTBF, MTTR, and MTTF together for a comprehensive look at each asset.
To learn more, see the 7 Most Important Maintenance Metrics.