Pump station reliability over a 1-year mission (R(t))
A reliability block diagram evaluated at a mission time — two redundant pumps with exponential (MTBF) and Weibull failure distributions. The engine computes R(t) for each block from its distribution and rolls it up to the system reliability at t = 8760 hours.
For the reliability engineer sizing a mission
What this shows
Static reliabilities are the entry point; real RAMS work is reliability over a mission. Here mission: 8760 (one year in hours) turns each block's failure distribution into an R(t): the controller and Pump A use an exponential model from their MTBF, while Pump B uses a Weibull (β = 1.5, so a gently increasing hazard — wear-out).
The engine evaluates R(t) per block and composes it. Pump A's e^(−8760/10000) ≈ 0.42 and Pump B's e^(−(8760/12000)^1.5) ≈ 0.54 combine in parallel to ≈ 0.73, then multiply by the controller in series — the headline reads R(t=8760) = …. Change the mission time and every figure, and the importance ranking, recomputes. Constant R= blocks still work and mix freely with distributions.