7 7.7. Results 169 Figure 7.4 shows that for a brand new pipe: (a) Agent-G performs maintenance on the pipe at approximately 32 years old; (b) Agent-E opts to replace the pipe when it is around 35 years old, which may be attributed to the presence of elements with higher severity levels in that specific episode; (c) CBM chooses not to act, which results in the least expensive policy in this comparison. However, it is observed that some pipe sections reach severity level k =5 throughout the episode. Not taking any action is deemed risky since progressing to k =F becomes more likely and incurs higher costs; (d) SchM e!ectively controls severity levels but is more expensive than Agent-G’s policy due to more frequent maintenance actions. k=1 k=2 k=3 k=4 k=5 k=F 0.00 0.25 0.50 0.75 1.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Time horizon Action at =0 at =1 at =2 Total Policy Costs:. -€22.2K [Maintenance: -€22.2K, Replace: €0.0K, Failure: €0.0K] Total Reward: -0.20 (a) Agent-G k=1 k=2 k=3 k=4 k=5 k=F 0.00 0.25 0.50 0.75 1.00 Total Policy Costs:. -€124.6K [Maintenance: €0.0K, Replace: -€24.6K, Failure: -€100.0K] Total Reward: -0.90 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Time horizon Action at =0 at =1 at =2 (b) Agent-E k=1 k=2 k=3 k=4 k=5 k=F 0.00 0.25 0.50 0.75 1.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Time horizon Action at =0 at =1 at =2 Total Policy Costs.: -€236.2K [Maintenance: -€11.6K, Replace: -€24.6K, Failure: -€200.0K] Total Reward: -1.70 (c) Condition-based Maintenance (CBM) k=1 k=2 k=3 k=4 k=5 k=F 0.00 0.25 0.50 0.75 1.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 Time horizon Action at =0 at =1 at =2 Total Policy Costs.: -€132.6K [Maintenance: -€8.0K, Replace: -€24.6K, Failure: -€100.0K] Total Reward: -1.00 (d) Scheduled Maintenance (SchM) Figure 7.5: Policies behaviour over an episode for a pipe aged 25, showing the health vector over the pipe age and actions per policy: (a) Agent-G, (b) Agent-E, (c) Conditionbased Maintenance (CBM), and (d) Scheduled Maintenance (SchM). Figure 7.5 shows that for a pipe aged 25: (a) Agent-G exhibits increased activity, indicating more frequent maintenance actions, especially as the pipe ages to 50,
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