BlockSim Example: CM Triggered by Subsystem Down

Purposes
The purpose of this example is to illustrate how to model the case when CM is triggered by failure of subsystem. (Limitation: Cannot model subsystem with more than two devices in parallel or more complex structure; subdiagram can be used to model more complex subsystems)

Description
Three devices A, B and C are in parallel. A and B form a subsystem AB. Only both A and B fail (subsystem AB fails), then start to repair A and B. Device C is parallel with subsystem AB. The repair of C depends on its failure. When C fails, then start to repair C.

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



Reliability of all blocks follow Weibull distribution with Beta =1.5 and Eta=500 hours.

Block A and Block B are belonging to maintenance group MG_AB.

CM of Block A and B are set to "When found failed during an inspection". The CM duration is 120 hour. Upon repair, they are as good as new.

There is an inspection for both block A and B. The inspection is performed based on events in maintenance group MG_AB. If "Block fails" or "Start of corrective maintenance" event occurs for any of the blocks in the maintenance group MG_AB, then the inspection is performed. The inspection duration is set to "Immediate Repair" and upon inspection; the device is restored to same as it was when it failed (as bad as old).

CM of Block C is performed upon failure of Block C and the duration is 20 hours. It is as good as new upon repair.

Block Up/Down plot
The system event log is shown in Figure belwo and is as follows:


 * 1) At 271, Block C fails and get repair at 291.
 * 2) At 331, Block B fails. Since the subsystem AB is not down (Both A and B fails, then subsystem AB fails), Block B is waiting for repair opportunity after its failure. (Failure of Block B cannot trigger inspection of Block B, but this failure would trigger the inspection of Block A. However, Block A doesn't have failure at this time, thus nothing happens).
 * 3) At 381, Block A fails and subsystem AB fails. Subsystem fails trigger the inspection and then inspection triggers CM. (failure of Block A triggers an inspection on Block B, and Block B has failure at this point. Thus CM of Block B is performed. Performing CM on Block B triggers the inspection of Block A and Block A also has failure at this time, thus CM of Block A is performed too.)
 * 4) At 501, both Block A and B are restored.
 * 5) At 791, Block B fails and is waiting for repair opportunity.
 * 6) At 943, Block C fails and get restored at 963.
 * 7) At 1358, Block A fails and subsystem AB fails, triggering CM for Block A and B.
 * 8) At 1478, both Block A and B are restored.