MTTx Terminology

When it comes to asset reliability measurement all the different MTTx acronyms start to appear but sometimes is not clear to everybody the exact meanings of these terms.
In this post I want to give a very simple explanation of these reliability KPIs.

• MTTD – Mean Time To Detect – How long it takes to discover a problem.
• MTTK – Mean Time to Know – How long it takes to understand the problem.
• MTTR – Mean Time To Repair – How long it takes to fix the problem.
• MTTF – Mean Time To Failure – Amount of time the system is available and operating. Also known as “uptime”.
• MTBF – Mean Time Between Failures – Amount of time that elapses between one failure and the next.

MTBF is the sum of MTTF and MTTR, the total time required for a device to fail and that failure to be repaired.
MTBF = MTTR + MTTF

Here is a nice representation for these KPIs.