Allen-Bradley 1756-L72S GuardLogix Safety Processor – ControlLogix Safety Series
When a safety-rated processor fails or goes missing in a functional-safety application, the consequences extend far beyond a production stoppage. Without a certified safety controller at the heart of the control architecture, emergency stop circuits lose their integrity, safety-rated I/O cannot be validated, and the entire SIL-rated loop collapses — exposing personnel, equipment, and regulatory compliance to unacceptable risk. In high-hazard environments such as chemical reactors, press lines, and oil & gas separators, that gap between a failed processor and a replacement arriving on-site is measured not in dollars but in potential incidents.
The 1756-L72S occupies a well-defined position within Rockwell Automation’s ControlLogix Safety platform: it is the mid-range safety processor that pairs a 4 MB standard memory partition with a 2 MB safety memory partition, delivering the computational headroom required for medium-to-large safety programs without the cost overhead of the flagship L73S. Globally, the GuardLogix family has become the reference architecture for TÜV-certified SIL 2 machine safety and process safety applications, deployed across tens of thousands of installations in automotive, pharmaceutical, and energy sectors.
Technical Specifications
Electrical
- Backplane Current Draw: 1.2 A @ 5 VDC; 3.0 mA @ 24 VDC
- Power Dissipation: 6.1 W (typical)
- Backplane Interface: ControlLogix 1756 chassis backplane
Memory & Processing
- Standard Memory: 4 MB (user program + data)
- Safety Memory: 2 MB (dedicated, hardware-partitioned)
- I/O Capacity: Up to 128,000 I/O points (standard); safety I/O via CIP Safety on EtherNet/IP or DeviceNet Safety
- Tasks: Up to 32 tasks, 100 programs per task
- Motion Axes: Up to 100 axes (coordinated motion)
Mechanical
- Form Factor: Single-slot ControlLogix module
- Dimensions: 94.0 mm H × 34.5 mm W × 128.3 mm D (approximate)
- Weight: ~200 g
- Mounting: 1756 chassis, any slot
Environmental
- Operating Temperature: 0 °C to +60 °C
- Storage Temperature: −40 °C to +85 °C
- Relative Humidity: 5–95% non-condensing
- Vibration: IEC 60068-2-6 compliant
- Shock: IEC 60068-2-27 compliant
- Enclosure Rating: Open-type (requires IP54 or better enclosure)
Safety & Certifications
- Safety Integrity Level: SIL 2 per IEC 61508 (TÜV Rheinland certified)
- Performance Level: PLd per ISO 13849-1
- Agency Approvals: UL, CE, CSA, C-Tick, ATEX Zone 2 (with appropriate housing)
- Industry Standard Reference: IEC 61508 Ed. 2, IEC 62061, ISO 13849-1:2015
Key Features & Benefits
- Hardware-Partitioned Safety Memory — The 2 MB safety partition is physically isolated from the standard program space, preventing any standard task from corrupting safety logic; this architecture is a prerequisite for TÜV SIL 2 certification and eliminates the need for a separate safety relay panel in many applications.
- CIP Safety Protocol Support — Native CIP Safety over EtherNet/IP enables certified safe communication to distributed safety I/O (e.g., 1791DS, 1734-IB8S) at up to 100 Mbps, reducing wiring costs by up to 60% compared to hardwired safety bus topologies.
- Integrated Standard + Safety Control — A single 1756-L72S replaces what previously required a standard ControlLogix processor plus a dedicated safety relay system, cutting panel footprint and reducing mean time to repair (MTTR) by consolidating diagnostics into one Studio 5000 project.
- 100-Axis Coordinated Motion — Supports up to 100 servo axes via SERCOS or EtherNet/IP, making it suitable for multi-axis press lines and robotic welding cells where motion and safety interlocks must be tightly synchronized.
- IEC 61508 SIL 2 Certified — Third-party TÜV Rheinland certification means the processor’s PFH (Probability of dangerous Failure per Hour) is documented and auditable, satisfying functional safety management requirements under IEC 61511 for process industries.
- Seamless Studio 5000 Integration — Safety and standard logic coexist in a single Logix Designer project, eliminating the dual-tool workflow required by competing safety PLC platforms and reducing engineering hours per project by an estimated 20–30%.
Industry & Equipment Applications
- Automotive Manufacturing — Robotic welding cells, stamping press lines, and body-in-white assembly stations where SIL 2 emergency stop and light curtain integration is mandatory per ISO 10218-2.
- Oil & Gas Processing — Wellhead control panels, compressor station ESD (Emergency Shutdown) systems, and pipeline SCADA nodes requiring IEC 61511 functional safety compliance.
- Chemical & Petrochemical — Reactor interlock systems, burner management systems (BMS per NFPA 86), and high-pressure vessel protection loops.
- Pharmaceutical & Life Sciences — Cleanroom HVAC interlocks, autoclave control, and filling line safety gates where 21 CFR Part 11 audit trails must coexist with SIL-rated safety functions.
- Power Generation & Utilities — Turbine overspeed protection, boiler drum level safety loops, and substation automation panels requiring IEC 61850 interoperability alongside safety logic.
- Material Handling & Intralogistics — High-bay warehouse conveyors, automated storage and retrieval systems (AS/RS), and palletizing robots where zone-based safety and coordinated motion must operate concurrently.
System Integration & Compatible Parts
Upstream / Power & Chassis
- 1756-A7, 1756-A10, 1756-A13, 1756-A17 — ControlLogix chassis (7, 10, 13, 17 slot)
- 1756-PA72, 1756-PB72 — ControlLogix AC/DC power supplies
Communication Modules
- 1756-EN2T, 1756-EN2TR — EtherNet/IP bridge modules for CIP Safety I/O
- 1756-DNB — DeviceNet Scanner for legacy safety device networks
- 1756-CN2 — ControlNet bridge for redundant media topologies
Safety I/O
- 1791DS-IB12 — 12-point 24 VDC safety digital input module
- 1791DS-OB8 — 8-point 24 VDC safety digital output module
- 1734-IB8S — POINT Guard I/O safety input module
Equivalent / Upgrade Path
- 1756-L71S — Lower memory (2 MB standard / 1 MB safety); suitable substitute only if safety program size is confirmed below 1 MB and standard program below 2 MB.
- 1756-L73S — Higher memory (8 MB standard / 4 MB safety); direct upgrade when project growth exceeds 1756-L72S capacity.
- 1756-L72 — Standard (non-safety) ControlLogix processor; NOT a valid substitute for any safety-rated application.
Our Quality Assurance Process
- Visual & Physical Inspection — Every unit is examined for label integrity, connector pin condition, housing cracks, and firmware revision sticker. Units with evidence of rework, re-marking, or counterfeit labeling are quarantined and rejected.
- Functional Power-On Test — The processor is seated in a live 1756 chassis and powered on. We verify that the OK LED reaches solid green, the processor enters RUN mode, and no fault codes are logged in the controller diagnostics.
- Firmware Version Verification — Firmware revision is read via RSLinx and cross-referenced against Rockwell’s published revision history to confirm authenticity and compatibility with current Studio 5000 releases.
- Documentation Package — Upon request, we can provide: test report, high-resolution photos of all label faces, firmware screenshot, and a certificate of conformance. For critical safety applications, a third-party inspection report can be arranged.
How to Order
- Submit Your Inquiry — Send your part number, required quantity, target delivery date, and destination country to support@konmask.com or use the inquiry form on this page.
- Receive Quotation — Our technical team will respond within 24 hours with availability, lead time, unit price (EXW/FOB Xiamen), and any applicable export documentation requirements.
- Confirm & Ship — Upon order confirmation and payment, we arrange export packaging, generate a commercial invoice and packing list, and dispatch via your preferred freight forwarder or our recommended carrier.
Why Choose Konmask.com?
- Specialist Inventory — We focus exclusively on industrial automation components from Rockwell Automation, Siemens, ABB, Schneider Electric, and Honeywell — no consumer electronics, no diluted catalog.
- Traceable Stock — Every unit in our inventory carries documented sourcing records. We do not mix untraceable spot-market stock with verified inventory.
- Technical Pre-Sales Support — Our team includes engineers with hands-on ControlLogix commissioning experience. We can advise on firmware compatibility, chassis slot planning, and CIP Safety network design before you commit to a purchase.
- Global Export Experience — We have shipped to over 40 countries, with experience navigating EAR99 classification, CE documentation, and destination-country import requirements for industrial control equipment.
- 24-Hour Response Commitment — Every inquiry submitted via email or the website form receives a substantive response — not an auto-reply — within one business day.
Frequently Asked Questions
Q: What is the difference between the Allen-Bradley 1756-L72S and the 1756-L72 for a safety application?
A: The 1756-L72S includes a hardware-partitioned 2 MB safety memory and is TÜV-certified to IEC 61508 SIL 2. The standard 1756-L72 has no safety partition and cannot be used as the safety controller in a GuardLogix safety system — it can only serve as the standard controller partner in a dual-chassis GuardLogix 1.x architecture. For any SIL-rated safety function, the 1756-L72S (or equivalent L7xS variant) is mandatory.
Q: Can the Allen-Bradley 1756-L72S GuardLogix processor be used as a drop-in replacement for an older 1756-L62S in an existing ControlLogix safety system?
A: Yes, with firmware and project migration steps. The 1756-L72S uses the same chassis slot and backplane interface as the L62S. You will need to upgrade the Studio 5000 / RSLogix 5000 project to a compatible revision, update the controller properties to reflect the new catalog number, and re-verify the safety task signature after download. Rockwell Automation’s migration guide (Publication 1756-UM020) covers the full procedure.
Q: What is the lead time for the 1756-L72S GuardLogix processor and do you offer expedited shipping for urgent plant shutdowns?
A: Lead time depends on current stock levels and your destination. In-stock units typically ship within 1–3 business days of order confirmation. For urgent plant shutdown or emergency maintenance situations, contact us directly at support@konmask.com with “URGENT” in the subject line — we prioritize these inquiries and can arrange same-day dispatch for confirmed orders placed before 14:00 CST.
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