Full definition
A reliability metric representing the average operating time between consecutive failures of a repairable system, calculated as: MTBF = Total Operating Time / Number of Failures. Higher MTBF indicates greater reliability. Example: if a pump operates 8,000 hours and experiences 2 failures, MTBF = 4,000 hours. MTBF is the primary reliability KPI for maintenance departments and is used for: spare parts inventory planning, maintenance interval optimization, reliability improvement tracking, and equipment comparison/selection. Typical industrial MTBF targets: critical equipment >8,000 hours (should approach 20,000+ hours with good maintenance), general equipment >4,000 hours. MTBF is used alongside MTTR to calculate Availability: A = MTBF / (MTBF + MTTR). For new equipment selection, MTBF data (from manufacturer or industry databases per ISO 14224) helps predict maintenance costs and spare parts requirements. Limitation: MTBF assumes a constant failure rate (random failures) — it does not capture early-life (infant mortality) or wear-out failure patterns. For components with distinct wear-out characteristics (belts, bearings, seals), age-based replacement using Weibull analysis is more appropriate than MTBF-based planning. Per IEEE 1413, MIL-HDBK-217 (electronics), and ISO 14224 (petroleum/petrochemical).