Redundant pump failure (AND gate)
The smallest quantified fault tree — two redundant pumps in an AND gate, so the system fails only if both fail. One minimal cut set, no single point of failure, with a computed top-event probability.
For the reliability engineer sizing redundancy
What this shows
The canonical reliability argument for redundancy. The top event occurs only when both pumps fail, so the gate is an AND (drawn as the flat-bottomed dome). The engine computes the one minimal cut set {PA, PB} (order 2, boxed in red) and — because no single component alone causes the top event — reports no single point of failure.
P(top) is computed, not drawn. With independent basic events, P(top) ≈ P(PA)·P(PB) = 1.0e-4 (rare-event). Adding a second pump turned two 1-in-100 components into a 1-in-10,000 system — exactly the quantified payoff redundancy is meant to deliver.