MTBF / MTTR Reliability Analysis
Mean Time Between Failures / Mean Time To Repair
Failure Records
Operating Hours (h)
Repair Time (h)
Formula
MTBF = Total Operating Hours / Number of Failures
MTTR = Total Repair Hours / Number of Failures
Availability = MTBF / (MTBF + MTTR)
R(t) = e^(-t/MTBF) (exponential distribution)
An equipment engineer logged 6 failures of an injection molding machine over six months, with run times before each failure of 120, 85, 200, 60, 150, and 95 hours, plus each repair duration. The MTBF calculator computes mean time between failures, MTTR, and predicts reliability at a queried time — the basis for setting preventive maintenance intervals.
Run time before 6 failures: 120+85+200+60+150+95 = 710 h. MTBF = 710/6 = 118.3 h. Repair time: 2.5+1.0+3.0+4.5+2.0+3.5 = 16.5 h, MTTR = 16.5/6 = 2.75 h. Availability A = 118.3/(118.3+2.75) = 97.7%. Query t=100 h: R(100) = e^(-100/118.3) = 43.2%. Recommend shortening the PM interval to every 80 hours.
FAQFrequently Asked Questions
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