Example The following figure shows a reaction system in which the temperature increases with the feed rate of flow-controlled stream D. Heat is removed by water circulation through an exchanger. Normal reactor temperature is 200 F, but a catastrophic runaway will start if the reactor temperature reaches 300 F.

Example In view of this situation, 1.The reactor temperature is monitored; 2.Rising temperature is alarmed at 225 F 9see horn); 3.An interlock shuts off stream D at 250 F, stopping the reaction (see solenoid and valve A); 4.The operator can initiate the interlock by pushing the panic button.

Assumptions Secondary failures are neglected. The alarm signal always reaches the operator whenever the horn sounds