MTTR stands for Mean Time to Repair, a metric used to measure the effectiveness of maintenance and repair operations. It is calculated by taking the total downtime for a specific equipment or system and dividing it by the number of repairs performed. The result is the average time it takes to repair the equipment or system.
The MTTR metric is used to evaluate the efficiency of maintenance and repair operations, indicating how quickly equipment or systems can be returned to service after a failure. A lower MTTR value is generally considered better, as it indicates that equipment or systems are being repaired more quickly and downtime is minimized.
It is important to note that MTTR is a reactive metric; it only measures the time taken to repair failed equipment but not the time taken to prevent it from failing. Therefore, it should be used in conjunction with other metrics, such as MTBF (Mean Time Between Failures), which measures the time taken between two failures and indicates the reliability of equipment or systems, and preventative maintenance metrics, such as PM completion rate, to get a full picture of the maintenance and repair operations of an organization.
Mean Time To Repair (MTTR) is one of the critical metrics to improve OEE and reduce the length of breakdowns. The ultimate goal is to have zero breakdowns. But a breakdown has happened, so how can we return the equipment to production ASAP?
Two things are required:
- robust skillset (mechanical, electrical and controls, pneumatic and hydraulic);
- spare parts availability (interchangeability of existing stock)
Skillset or lack of knowledge
Skill improvement needs to be done based on Breakdown Analyses, which can include the following lean tools:
- Root Cause Analysis;
- Why-Why Analysis;
If one of the causes was “took a long time to repair” and spare parts were available, a particular skill needs to be improved, for example:
Equipment was down for extended periods because mechanics were troubleshooting the “top sealing assembly.” They had to alter temperature, sealing pressure, and dwell time to eliminate product leakage. From the example above, we can identify that the maintenance crew did not clearly understand setpoints, principles of operation, and other essential facts about the equipment.
Next steps – implement training and share with the entire team. We can utilize the following tools:
- Recurrence Matrix
- One Point Lessons
- Add training refreshers into the Training and Education plan
We would stock every part locally in a perfect world with unlimited R&M budgets for spare parts. But every manufacturing facility has a budget, so a balance needs to be found between parts availability and equipment criticality.
A machine ledger is a great tool for identifying the importance of equipment, which will lead to maintaining the necessary stock.
Another way to reduce the necessity of having all parts – is the interchangeability of existing stock. Instead of using just the OEM part (which usually carries a unique number), add the manufacturer’s part number to CMMS, so next time, for example, you will need a PLC input card for rotary filler manufactured by S&N; However, the same part can be already in stock but assigned to the case packer made by Bosch.
Also, suppose you have a vital skill set in your team. In that case, parts can be reviewed and made interchangeable between different manufacturers; for example, OMRON normally opens photo-eye instead of Allen-Bradley one.
To summarize, Analysis of lost time is very important, but it’s crucial to follow up on all actions related to “lack of skills or knowledge” and parts inventory management.