Template:Rotation

Standby Rotation

Purpose

This example illustrates the use of state change triggers (SCT) in BlockSim Version 8 by using a simple standby configuration. Note that this example could also be done using the standby container functionality in BlockSim.

More specifically, the following settings are illustrated:

1. State Upon Repair: Default OFF unless SCT overridden
2. Activate a block if any item from these associated maintenance group(s) goes down
   

Statement

Assume three devices A, B and C in a standby redundancy (or only one unit is needed for system operation). The system begins with device A working. When device A fails, B is turned on and repair actions are initiated on A. When B fails, C is turned on and so forth.

BlockSim Solution

The BlockSim model of this system is shown in the figure below.

• The failure distributions of all three blocks follow a Weibull distribution with Beta = 1.5 and Eta = 1,000.
• The repair distributions of the three blocks follow a Weibull distribution with Beta = 1.5 and Eta = 100.
• After repair, the blocks are "as good as new."

There are three maintenance groups, 2_A, 2_B and 2_C, set as follows:

• Block A belongs to maintenance group 2_A.
  • It has a state change trigger.
    • The initial state is ON and the state upon repair is "Default OFF unless SCT overridden."
    • If any item from maintenance group 2_C goes down, then activate this block.

• Block B belongs to maintenance group 2_B.
  • It has a state change trigger.
    • The initial state is OFF and the state upon repair is "Default OFF unless SCT overridden."
    • If any item from maintenance group 2_A goes down, then activate this block.

• Block C belongs to maintenance group 2_C.
  • It has a state change trigger.
    • The initial state is OFF and the state upon repair is "Default OFF unless SCT overridden."
    • If any item from maintenance group 2_B goes down, then activate this block.

• All blocks A, B and C are as good as new after repair.

System Events

The system event log is shown Block Up/Down plot below, for a single run through the simulation algorithm and is as follows:

1. At 73, Block A fails and activates Block B.
2. At 183, Block B fails and activates Block C.
3. At 215, Block B is done with repair. At this time, Block C is operating, according to setting, Block B is standby.
4. At 238, Block A is done with repair. At this time, Block C is operating. Thus Block A is standby.
5. At 349, Block C fails and activates Block A.
6. At 396, Block A fails and activates Block B.
7. At 398, Block C is done with repair. At this time, Block B is operating. Thus Block C is standby.
8. At 432, Block A is done with repair. At this time, Block B is operating. Thus Block A is standby.
9. At 506, Block B fails and activates Block C.
10. At 515, Block B is done with repair and keeps standby because Block C is operating.
11. At 536, Block C fails and active Block A.
12. At 560, Block A fails and active Block B.
13. At 575, Block B fails and put a request to active Block C. However, Block C is under repair at the time. Thus when Block C is done with repair at 606, the OFF setting is overwritten and it is operating immediately.
14. At 661, Block C fails and put a request to active Block A. However, Block A is under repair at the time. Thus when Block A is done with repair at 699, the OFF setting is overwritten and it is operating immediately.
15. Block B and Block C are done with repair at 682 and at 746 respectively. However, at these two time point, Block A is operating. Thus they are both standby upon repair according to settings.