Template:Tires

Tire Example

Purposes

The purpose of this example is to illustrate the following options in SCT:

1. State Upon Repair: Always ON, Always OFF
2. Activate a block if any item from these associated maintenance group(s) goes down
3. Deactivate a block if any item from these associated maintenance group(s) is restored
4. Deactivate a block if any item from these associated maintenance group(s) goes down
5. Activate a block if any item from these associated maintenance group(s) is restored

Description

A car has four regular tires and a spare tire. Each tire has two failure modes: Wear with Weibull distribution (Beta = 1.5,Eta = 600 hours) and Puncture with Exponential distribution (Mean = 2 months). The repair duration of both Wear and Puncture failures follow Weibull distribution (Beta = 1.5,Eta = 100hours). However, Wear is repaired as good as new, Puncture is repaired as bad as old. When regular tires fail, the spare tire is activated; upon regular tire is restored, the spare tire is deactivated and put back.

BlockSim Solution

To model this system, six diagrams are created: Car, Tire_1, Tire_2, Tire_3, Tire_4 and Spare. Car is the main diagram. In the Car diagram, the five subdiagram blocks Tire_1, Tire_2, Tire_3, Tire_4 and Spare are pointed to other five diagrams with the same names.

In diagram Car, subdiagram blocks Tire_1, Tire_2, Tire_3 and Tire_4 belong to maintenance group "Main Tires".

In diagram Tire_1, there are two blocks in series. Block Wear 1 represents Wear failure mode and Puncture 1 represents Puncture failure mode for tire 1 respectively. Block Wear 1 belongs to maintenance group "Wear_1" and Block Puncture 1 belongs to maintenance group "Puncture_1".

Block Wear 1 has State Change Triggers (SCT), its initial state is ON, and the state upon repair is "Always On". If any item from maintenance group "Puncture_1" goes down, deactivate this block and if any item from maintenance group "Puncture_1" is restored, activate this block. 

Block Puncture 1 also has State Change Triggers (SCT), its initial state is ON, and the state upon repair is "Always On". If any item from maintenance group "Wear_1" goes down, deactivate this block and if any item from maintenance group "Wear_1" is restored, activate this block.

Blocks in other three diagrams (Tire_2, Tire_3 and Tire_4) follow the same logic.

In diagram Spare, there are two blocks in series. Block Wear_S represents Wear failure mode and Puncture_S represents Puncture failure mode for spare tire respectively. Block Wear_S belongs to maintenance group "Wear_S" and Block Puncture_S belongs to maintenance group "Puncture_S".

Block Wear_S has State Change Triggers (SCT), its initial state is OFF, and the state upon repair is "Always OFF". If any item from maintenance group "Puncture_S" goes down, deactivate this block and if any item from maintenance group "Puncture_S" is restored, activate this block. If any item from maintenance group "Main Tires" goes down, activate this block and if any item from the maintenance group "Main Tires" is restored, deactivate this block. 

Block Puncture_S has State Change Triggers (SCT), its initial state is OFF, and the state upon repair is "Always OFF". If any item from maintenance group "Wear_S" goes down, deactivate this block and if any item from maintenance group "Wear_S" is restored, activate this block. If any item from maintenance group "Main Tires" goes down, activate this block and if any item from the maintenance group "Main Tires" is restored, deactivate this block.

Blocks Up/Down plot

The system event log is shown in Figure below and is as follows (only blocks have failures are plot):

1. At 91, Block Puncture 2 fails and brings down subdiagram Tire_2. At the same time, it turns Block Wear 2 OFF. Subdiagram Tire_2 goes down and actives Block Wear_S and Puncture_S, and subdiagram Spare is turn ON too.
   
2. At 253, Block Puncture 2 is done with repair. According to setting, it is always ON upon repair (is restored). The restoration of Block Puncture 2 activates Block Wear 2 and thus subdiagram Tire_2 is ON. The restoration of subdiagram Tire_2 deactives Block Wear_S and Puncture_S, and subdiagram Spare is turn OFF too.
   
3. At 427, Block Puncture 2 fails again and brings down subdiagram Tire_2. At the same time, it turns Block Wear 2 OFF. Subdiagram Tire_2 goes down and actives Block Wear_S and Puncture_S, and subdiagram Spare is turn ON too.
   
4. At 442, Block Wear_S fails and brings down subdiagram Spare. At the same time, it turns Block Puncture_S (file crashed, to be continous later)