Application Scenarios
A automotive stamping plant operated a press line with interlocked light curtains, safety gates, and two-hand control stations, all monitored by a dedicated safety PLC that communicated with the main control system through hardwired signals. The engineering team wanted to eliminate the separate safety controller and the associated wiring complexity while maintaining SIL 3 certification. By deploying the 1756-L72S in the main ControlLogix rack, the plant consolidated standard press sequencing and safety interlocks into one chassis, programming both in Studio 5000 with clearly partitioned standard and safety tasks. The 2 MB safety memory accommodated the full interlock logic for the line’s twelve safety zones, while the 4 MB standard memory handled the press cycle logic, recipe management, and operator interface data. For facilities running mixed standard-and-safety applications, this processor eliminates the integration seam between two separate control architectures.
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1756-L72S |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Category | GuardLogix integrated safety processor |
| Standard User Memory | 4 MB |
| Safety Memory | 2 MB |
| Safety Certification | SIL 3 / PLe / Cat. 4 |
| Communication | 1 × built-in USB programming port |
| Nonvolatile Storage | Secure Digital (SD) card (1 GB included with L7 series) |
| Power Backup | Energy Storage Module (ESM), lithium-battery-free |
| Supported Networks | EtherNet/IP, ControlNet, DeviceNet, DH+, Remote I/O, SynchLink (via communication modules) |
| Programming Software | Studio 5000 (formerly RSLogix 5000) |
| Operating Temperature | 0 °C to 60 °C (32 °F to 140 °F) |
| Certifications | UL, c-UL-us, CE, TÜV, ATEX, FM, C-Tick |
| Dimensions (W × H × D) | 292 mm × 240 mm × 164.52 mm |
Technical Principles and Innovative Values
- Partitioned Standard and Safety Execution: The 1756-L72S runs standard control tasks and safety tasks in separate memory partitions within the same controller, with the safety task certified to SIL 3. This means press sequencing logic and light curtain interlock logic can coexist in one chassis without compromising certification, eliminating the separate safety PLC and its hardwired handshake.
- ESM Eliminates Battery Maintenance: The Energy Storage Module replaces the lithium battery used in earlier ControlLogix generations, removing the periodic battery replacement task and the environmental burden of lithium disposal. For plants with dozens of controllers in inaccessible cabinets, this is a maintenance simplification that compounds over the controller’s service life .
- SD Card for Nonvolatile Program Storage: The 1756-L7 series uses Secure Digital memory instead of CompactFlash, providing faster read/write performance and better data integrity. The included 1 GB SD card stores the program and can be swapped for rapid recovery after a controller failure .
- Safety Partner Architecture: The 1756-L72S operates with a 1756-L7SP safety partner module in a redundant configuration for SIL 3 applications, where the safety partner monitors the primary processor’s safety task execution. This architecture provides the diagnostic coverage required for the highest safety integrity level without relying on external watchdog hardware.
