In short
Which Allen-Bradley parts to keep on the shelf — controllers, drives, I/O, networking, HMI.
Critical-spare recommendations
| Category | Why stock | Recommended qty |
|---|---|---|
| Power supplies (1756-PA72, 1769-PA4) | Whole-chassis SPOF | 1 per chassis type |
| CPU modules | Long lead when discontinued | 1 per running CPU |
| EtherNet/IP (1756-EN2T, 5069-AENTR) | Network outage halts cell | 1 per cell |
| Drives (PowerFlex 525/753) | High failure from heat/dust | 1 per HP class |
| HMIs (PanelView Plus) | Operator-blind shutdown | 1 per model |
Storage
- Power up electrolytic-cap drives yearly to reform caps.
- Anti-static bags + climate-controlled storage.
- Label firmware revision.
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