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This video builds a reliability block diagram, RBD for short, in ReliaEn and evaluates the reliability of the whole system.

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The system is a conveyor drive: a motor with a constant failure rate, and a gearbox that wears out.

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The drive stops if either one fails.

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Open the System menu and choose RBD Canvas.

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The canvas opens with the END terminal in view.

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Scroll left to bring START in as well.

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Press + Add Block and name the first block Exp1000: the motor.

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Drag the block between START and END.

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Double-click the block.

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In Block properties, Source is Manual parameters and Distribution is Exponential (λ).

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Type the failure rate λ, 0.001 per hour, and press OK.

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Add a second block, Wb2-2000: the gearbox.

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Drag it between Exp1000 and END.

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In its Block properties, choose Weibull 2P (β, η).

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Type the shape β, 2, and the scale η, 2000 hours, and press OK.

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Now draw the lines.

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Press on the small round port at the right edge of START, drag to the motor block and let go.

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Then from the motor's port to the gearbox.

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And from the gearbox's port to END: the 3 lines make the series path from START to END.

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Press Evaluate…

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In Evaluate system, type the mission time, 500 hours, and press OK.

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In RESULTS, the system survives the 500-hour mission with probability 0.5698.

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The system's mean time between failures, MTBF, is 757.87 hours, its B10 life 102.72 hours, and its median 602.42 hours.

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The plot shows the reliability of each block and of the system over operating time.

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The system curve lies below both blocks: a chain is weaker than its links.

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The sensitivity tornado shows how far the system MTBF moves when each block's scale changes by 10 percent.

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The motor moves it most.

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At 500 hours the motor's reliability is 0.6065 and the gearbox's is 0.9394.

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There are 2 minimal cut sets, each a single block: Exp1000 fails and Wb2-2000 fails.

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Each block is a single point of failure.

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An independent simulation of 20,000 runs gives 0.5607 and agrees with the analytic result.

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The importance measures name the motor: Exp1000 carries the highest Birnbaum importance, 0.9394, so improving the motor moves the system most.

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And the service intervals give the system's operating time for each target: it stays above 90% reliability until 102.7 hours.

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The next video turns to the FMEA study and criticality.