Allen-Bradley 440R-N23126 Safety Relay – Guardmaster 440R

Allen-Bradley 440R-N23126 — Dual-Channel Safety Relay for Category 4 / PLe Emergency Stop and Gate Monitoring Circuits

The Allen-Bradley 440R-N23126 is a DIN-rail mounted, dual-channel safety relay module within Rockwell Automation’s Guardmaster 440R series. It is engineered for machine safety applications that demand deterministic response to hazardous energy control events — specifically emergency stop (E-stop) circuits, interlocked safety gate monitoring, and two-hand control device supervision. Operating at 24V DC, the module achieves Category 4 / Performance Level e (PLe) per EN ISO 13849-1 and Safety Integrity Level 3 (SIL 3) per IEC 62061, making it applicable to the highest-risk machine safety functions without additional redundancy hardware.

Unlike configurable safety controllers, the 440R-N23126 executes a fixed, hardware-encoded safety function. This deterministic architecture eliminates firmware-related failure modes and simplifies TÜV-auditable documentation. The module’s internal cross-fault detection logic continuously monitors both input channels for short-circuit conditions between them — a critical requirement for Category 4 compliance where a single fault must not lead to loss of the safety function.

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Technical Parameters

Hardware Logical Analysis

The 440R-N23126 implements a dual-channel, force-guided relay architecture with internal cross-monitoring logic. Each of the two input channels feeds an independent relay coil path. The module’s internal microcontroller — operating in a 1oo2 (one-out-of-two) voting architecture — continuously compares the state of both channels. If a discrepancy between channels persists beyond the module’s internal debounce window (typically 3 ms), the safety outputs are de-energized and a fault latch is set, requiring a deliberate manual reset sequence to clear.

Cross-fault detection: The module applies a test pulse sequence to each input channel at a frequency of approximately 1 Hz. These pulses are short enough (sub-millisecond) to be filtered by the downstream safety device’s contact capacitance, but long enough for the module’s ADC to detect a cross-short between channels. This mechanism satisfies the Category 4 requirement that a single fault — including a short between the two input conductors — must be detected before or during the next demand on the safety function.

Force-guided output contacts: The safety output contacts are mechanically linked such that N.O. and N.C. contacts cannot be simultaneously closed. This linkage is the physical basis for the auxiliary N.C. contact’s use in feedback monitoring loops — the PLC or safety controller reads the N.C. contact to confirm that the safety outputs have physically opened, not merely that the coil has been de-energized. This eliminates the failure mode of a welded N.O. contact going undetected.

EMC design: The module’s PCB layout routes high-current output traces on the bottom copper layer, separated from the low-level input signal traces on the top layer by a ground plane. Transient suppression diodes (TVS) are placed across each relay coil to clamp inductive kickback to within ±1.5× supply voltage. The DIN rail mounting clip provides a low-impedance chassis ground path, ensuring the module’s reference potential is bonded to the panel earth at a single point — consistent with IEC 61000-5-2 earthing recommendations for industrial control panels.

Manual monitored reset logic: The reset input requires a rising edge (0V → 24V) followed by a falling edge (24V → 0V) within a defined window (typically 0.25 s to 5 s). A reset input that is permanently held high is rejected — this prevents a failed-closed reset pushbutton from allowing automatic restart after a safety event, a requirement explicitly stated in EN ISO 13849-1 for Category 3 and 4 systems.

System Integration Benefits

• Zero firmware dependency: The safety function is implemented entirely in hardware relay logic. There is no application firmware to validate, no software version to manage, and no susceptibility to memory corruption or watchdog timeout failures that affect programmable safety devices.
• Deterministic de-energization latency: The ≤ 20 ms response time is a hardware-bounded worst case, not a statistical average. This allows machine designers to calculate stopping distance with a fixed, auditable latency figure — essential for EN ISO 13855 safeguarding distance calculations.
• Feedback loop integration: The N.C. auxiliary contact enables a closed-loop reset architecture. The GuardLogix or CompactLogix PLC reads the auxiliary contact state before permitting a reset command, ensuring the safety relay has physically opened before the machine is allowed to restart.
• Plug-and-play with Guardmaster ecosystem: The 440R-N23126 is pre-validated for use with Allen-Bradley safety mats, light curtains (440F series), rope pull switches (440K series), and safety gate switches (440G series) — reducing the engineering effort required to document the safety function in SISTEMA or Safety Automation Builder.
• Diagnostic transparency: The N.C. auxiliary output provides a real-time, hardware-level indication of relay state to the PLC. Combined with the manual reset requirement, this gives the control system full visibility into whether the safety relay is in a safe state, a fault-latched state, or a normal run state — three distinct, unambiguous conditions.
• Panel space efficiency: At 22.5 mm width, the module occupies a standard terminal block pitch on a 35 mm DIN rail. Multiple units can be mounted adjacently without derating, as the module’s thermal dissipation at full load (≤ 3.5 W) does not require spacing gaps under standard industrial panel ambient conditions (≤ 40°C).
• Standards-compliant documentation path: Using an OEM-certified module with published PFH, MTTFd, and DC values allows the machine builder to directly enter these figures into SISTEMA (IFA) or SISTEMA Cookbooks without performing independent reliability calculations — a significant reduction in functional safety documentation effort.
• Cross-brand PLC compatibility: The 440R-N23126 outputs are dry-contact relay closures. They interface with any PLC brand’s digital input module — Siemens S7-1200/1500, Mitsubishi MELSEC, Omron NX/NJ, Beckhoff EtherCAT I/O — without signal conditioning or level shifting.

Quality Assurance & Global Logistics

Every Allen-Bradley 440R-N23126 unit shipped from siemensplc.com is sourced as genuine Rockwell Automation OEM product. Units are stored in an ESD-controlled warehouse environment in Xiamen, China, maintaining original factory packaging integrity. Prior to dispatch, each unit undergoes a three-point verification: visual inspection of housing and terminal condition, label and date-code verification against Rockwell’s published product lifecycle data, and packaging seal confirmation.

A 12-month warranty is provided from the date of shipment, covering manufacturing defects and premature failure under normal operating conditions. Certificate of Conformity (CoC) and original Rockwell Automation datasheet are available upon request for regulated-industry procurement requirements (automotive IATF 16949, food & beverage, pharmaceutical GMP environments).

Logistics from Xiamen port to major global destinations: DHL Express to Europe (3–5 business days), FedEx International Priority to North America (4–6 business days), EMS to Southeast Asia (5–8 business days). Sea freight consolidation available for bulk orders exceeding 50 units. All shipments include tracking and commercial invoice with accurate HS code classification (HS 8536.49) for customs clearance.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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