This simulator builds a small fault tree for a discharge system: the top event occurs if the outlet is blocked OR if both the duty pump and the standby pump fail. You can switch each basic event on and off to watch the gates light up, and you can enter event probabilities to compute the top-event probability.
• A 3D fault tree with three basic events (outlet blockage, duty pump, standby pump), an AND gate for both pumps and an OR gate with a top-event annunciator. • Sliders for outlet blockage probability, duty pump failure probability and standby pump failure probability, each from 0 to 0.5, and three manual event switches. • Four live readouts: top-event probability, both-pumps failure probability, whether the top event is active and the minimal cut sets. • Two presets: Only duty pump fails (AND gate and top event stay clear) and Both pumps fail (AND and top OR assert).
The logic is Top = A OR (B AND C), where A is the outlet blockage and B and C are the two pump failures. The minimal cut sets are {A} and {B, C}: A alone, or both pumps together, is enough to cause the top event. For independent basic events the top probability is P_top = qA + (1 - qA) qB qC, which corrects for the overlap; simply adding qA + qB qC would count the A-and-B-and-C case twice.
Basic-event probabilities are independent values for a fixed mission, not failure rates, and the model has no repair, timing, priority AND gates or common causes. The manual Boolean switches are independent of the probabilities you enter, so they show the logic path while the probability readouts come from the entered values alone.
A smallest group of basic events that together cause the top event. Here {A} alone and the pair {B, C} are the minimal cut sets.
Adding them counts the overlapping case where A, B and C all occur twice. The exact independent result is qA + (1 - qA) qB qC.
An AND gate asserts only when all its inputs are true, like both pumps failing. An OR gate asserts when any input is true, like blockage or the pump pair failing.
It uses independent fixed-mission probabilities with no repair, timing, priority AND gates or common causes.