Template:Standby with Delay (SCT Solution)

SCT with delay

Purposes

The purposes of this example is to illustrate how to apply SCT with delay.

Description

Three devices A, B and C are in parallel. 2 out of 3 are required to perform the task. Initially A and B are working, C is in standby status. If A or B fails, C will replace the failed one with some delay. After the failed device is restored, it will become a standby device. For example, If A fails, with 10 hours delay C will become active and replace A. After A is restored, it will become a standby device for B and C.

BlockSim Solution

The BlockSim modeling of this system is shown in Figure below.

In order to model the delay, three extra blocks AA, BB and CC are added to the diagram. Each of them fails every 10 hours (Normal distribution with mean 10 hours and standdard deviaiotn 0.0000001 hours). They operate even if system is down and repair durations for them are 0 (immediate repair). Block AA(BB/CC) is belong to maintenance group AA(BB/CC). They all have state change triggers. The initial state is OFF and the state upon repair is Always OFF. If Block A (B/C) goes down, then activate Block AA (BB/CC).