Allen-Bradley Guardmaster MSR125HP (440R‑D23171) Two-Hand Control Safety Relay
This unit is a dedicated two-hand control safety relay under the Guardmaster series of Rockwell Automation. It features dual-channel input, 2 NO safety contacts, Categoria 4 / Performance Level e (PL e) safety rating and removable terminals. Designed specifically for high-risk machinery requiring synchronized two-hand operation, it keeps operators’ hands within safe zones and prevents personal injuries.
- Spiegazione del codice modello
MSR125HP‑440R‑D23171 is a two-hand control safety relay of the Guardmaster series manufactured by Allen‑Bradley / Rockwell Automazione, U.S.A.. The model breakdown and corresponding order number are specified below:
| Segmento di codice | Descrizione |
| MSR | Codice della serie: Minotaur Safety Relay |
| 125 | Codice funzione: Two-hand control unit, compliant with Type III safety requirements of ISO 13851 |
| HP | Feature code: Alte prestazioni, equipped with removable terminals (differentiated from MSR125H with fixed terminals) |
| 440R‑D23171 | Numero dell'ordine: Exclusive Rockwell identification code, for 24V DC power supply and two-hand control function |
Key Ordering Information
Main Order Number: 440R‑D23171 (Standard version with removable terminals)
Modello alternativo: 440R‑D23168 (MSR125H, fixed terminals)
Compatible Model: 440R‑D23172 (with 0.5-second time delay function)
- Specifiche tecniche principali
| Categoria | Dati tecnici | Osservazioni |
| General Specifications | ||
| Tipo | Two-hand control monitoring safety relay | Compliant with Type III requirements of ISO 13851 |
| Tensione operativa | 24A DC (-15%/+20%) / 24V e (-15%/+10%) | Massimo. ripple voltage: 10% |
| Consumo energetico | Massimo. 3W | Low power consumption design |
| Protezione dall'ingresso | IP40 (Alloggiamento) / IP20 (Terminali) | Suitable for control cabinet installation |
| Caratteristiche di ingresso | ||
| Monitoring Channels | Dual channel (1NC + 1NO input) | Dedicated for two-hand control, synchronized triggering required |
| Tipo di ingresso | Dry contact signal | Compatible with two-hand control buttons and foot switches |
| Synchronization Time Window | ≤ 0.5 secondo | Operation beyond this window is deemed unsafe |
| Caratteristiche di uscita | ||
| Safety Contacts | 2 Normalmente aperto (NO) contatti | AC15: 230V/6A; DC13: 24V/6A |
| Auxiliary Output | Nessuno | Optimized for safety control |
| Livello di prestazione | PL e (Highest level) | Compliant with EN ISO 13849‑1 |
| Categoria di sicurezza | Categoria 4 | Compliant with EN IEC 61508 |
| Livello di integrità della sicurezza | SIL 3 | Meets requirements for high-risk applications |
| Caratteristiche fisiche | ||
| Dimensioni | 22.5mm × 99mm × 121mm | Montaggio su guida DIN, salvaspazio |
| Montaggio | 35Guida DIN standard da mm | Standard industrial installation |
| Temperatura operativa | -25°C~60°C | Wide temperature range for industrial environments |
| Terminali | Removable screw terminals | Cable cross-section: 0.25mm² ~ 2.5mm² |
| Certificazioni | UL, CSA, CE, TÜV | Conforme agli standard di sicurezza internazionali |
- Cross-Brand Compatibility List
| Marca | Modello sostitutivo | Descrizione della compatibilità |
| Allen-Bradley | MSR125H (440R‑D23168) | Identical functions, only differs in terminal type (fixed terminals) |
| Schmersal | SRB301‑24V (101190686) | General-purpose safety relay with 3 safety contacts; two-hand control logic needs reconfiguration |
| Siemens | 3SK1122‑1AB30 | Dedicated two-hand control relay, 2 safety contacts, 24A DC |
| Schneider Electric | XPSAC5121 | 24V CA/CC, 3 safety contacts; two-hand control requires additional programming |
| Omron | G9SA‑501 | Two-hand control unit, 2 safety contacts, STOP 0 stop category |
Suggerimento per la selezione: Choose dedicated two-hand control relays; match synchronization window and contact quantity; do not downgrade safety ratings; select terminals according to on-site demands.
- Full Model List of MSR Two-Hand Control Series
Modello Numero d'ordine Voltaggio Configurazione dei contatti Tipo di terminale Funzione speciale MSR125HP 440R‑D23171 24V CA/CC 2 NO safety contacts Removable Two-hand control, instantaneous output MSR125H 440R‑D23168 24V CA/CC 2 NO safety contacts Fisso Two-hand control, instantaneous output MSR125HP‑0.5s 440R‑D23172 24V CA/CC 2 NO safety contacts Removable Two-hand control, 0.5s delayed output MSR125H‑0.5s 440R‑D23169 24V CA/CC 2 NO safety contacts Fisso Two-hand control, 0.5s delayed output MSR125HP‑240V 440R‑D23173 240V e 2 NO safety contacts Removable Two-hand control, high voltage version Difetti comuni & Risoluzione dei problemi
| Fenomeno di guasto | Possibili cause | Soluzioni |
| Power indicator off | 1. Power disconnected or abnormal voltage | 1. Check power connection and voltage (20.4V~28.8V DC) |
| 2. Internal fuse blown | 2. Replace 2A internal fuse | |
| Safety contacts fail to activate | 1. Two buttons not synchronized (interval over 0.5s) | 1. Standardize operation to ensure synchronized actuation |
| 2. Fault in input channels | 2. Inspect buttons and wiring, replace defective parts | |
| 3. Incorrect reset mode setting | 3. Verify reset mode (automatic / manual) | |
| Frequenti falsi interventi | 1. Interferenza elettromagnetica | 1. Apply shielding and keep away from interference sources |
| 2. Loose cable connections | 2. Retighten cables and ensure reliable connection | |
| 3. Improper synchronization window | 3. Confirm fixed 0.5s synchronization window (non regolabile) | |
| Failed reset | 1. Safety circuit not fully closed | 1. Inspect all safety input devices |
| 2. Manual reset button not pressed | 2. Press reset button (under manual reset mode) | |
| 3. Internal component failure | 3. Replace the safety relay module |
Quick Troubleshooting Guide: Check power supply first, then synchronization. For inactive contacts, inspect inputs; for false tripping, eliminate interference; for reset failure, verify the whole safety circuit.
- Ambienti applicativi & Casi di settore
6.1 Scenari applicabili
Stamping & Bending Machinery: Presses, press brakes, shears and other metalworking equipment requiring two-hand operation
Injection & Molding Machinery: Mold area protection for injection molding machines and die-casting machines to prevent hand injuries
Assembly & Testing Tooling: Custom automated equipment with mandatory two-hand operation for operational safety
Welding & Cutting Equipment: Start-up control for welding robots and plasma cutters to avoid accidental activation
Macchine per l'imballaggio: Sealing and cutting stations with synchronized two-hand operation to protect operators
6.2 Not Recommended Scenarios
Single-button controlled equipment: Two-hand control function cannot be utilized, resulting in unnecessary cost
Outdoor harsh environments: IP40 rating is not suitable for outdoor installation
Highly corrosive environments: No anti-corrosion coating, incompatible with acid, alkali and corrosive substances
High vibration environments: Vibration exceeding 5g will shorten relay service life
6.3 Casi applicativi tipici
Caso 1: Two-Hand Start Safety System for CNC Press
Applicazione: Start control for 160-ton CNC press, preventing operators from reaching into the stamping zone
Configurazione: MSR125HP (440R‑D23171) + 2 mushroom-head two-hand buttons (mounted on both sides of machine, spacing ≥ 60cm)
Principio di funzionamento: Both buttons must be pressed synchronously within 0.5 second to close safety contacts and start the press. The machine stops immediately once either button is released.
Effetto: Complies with Category 4 / PL e standards, eliminating risks of hands entering hazardous areas during operation.
Caso 2: Mold Closing Safety Protection for Injection Molding Machine
Applicazione: Mold closing control for 200-ton injection molding machine, preventing pinching injuries during part removal
Configurazione: MSR125HP + two-hand buttons (mounted on both sides of control panel) + magnetic safety switch for safety gate
Principio di funzionamento: Mold closing can only be initiated when the safety gate is fully closed and both buttons are pressed synchronously. Mold movement stops instantly if the gate is opened or any button is released.
Effetto: Dual safety protection implemented, fully compliant with safety standards for rubber and plastics industry.
Caso 3: Two-Hand Coordinated Workstation for Automated Assembly Line
Applicazione: Press-fitting station for automotive component assembly line, two-hand operation required to activate the press head
Configurazione: MSR125HP + foot switch (auxiliary control) + two-hand buttons (main control)
Principio di funzionamento: Activate foot switch to clamp workpieces, then press both buttons synchronously to start the press head, ensuring operators’ hands stay in safe positions.
Effetto: Improves production efficiency while guaranteeing operator safety, ideal for mass production lines.
- Linee guida operative & Specifiche di installazione
- Two-hand button installation: Maintain a minimum spacing of 60cm between two buttons to prevent actuation with one single hand.
- Wiring rules: Adopt cross wiring for dual input channels to enhance fault detection capability.
- Reset mode selection
Ripristino automatico: System recovers automatically after fault removal, suitable for continuous production lines.
Ripristino manuale: Reset button must be pressed manually, recommended for high-risk applications.
- Maintenance schedule: Inspect contact status and wiring every 6 months to ensure stable and safe operation.
- Spare parts management: Prepare one identical relay as spare part to minimize downtime caused by equipment failure.
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