The Laien SR4P3A1B24 is a safety relay engineered for monitoring emergency stop switches, safety gate switches, and dual-channel PNP output safety light curtains. It is part of the SR series from Shandong Laien Optic-Electronic Technology Co., Ltd., a manufacturer specializing in industrial safety protection solutions. The SR4P3A1B24 is certified to the highest functional safety standards, achieving Performance Level e (PL e) and Safety Category 4 according to EN ISO 13849-1, and Safety Integrity Level 3 (SIL 3) according to EN 62061. This makes it suitable for safety-critical applications requiring maximum risk reduction.

At the core of the SR4P3A1B24's reliability is its dual-channel redundant architecture with self-monitoring circuitry. The device continuously verifies the integrity of its internal components and external wiring, ensuring that any fault—whether a short-circuit across input contacts or an internal component failure—is detected and the safety outputs are de-energized. The diagnostic coverage exceeds 99%, contributing to an impressive Mean Time to Dangerous Failure (MTTFd) of 111 years and an extremely low Probability of Dangerous Failure per Hour (PFHd) of 2.5×10⁻⁸. The safety function remains effective even if a single component fails, meeting the fault tolerance requirements of Category 4.

The SR4P3A1B24 provides three normally open (NO) safety contacts and one normally closed (NC) auxiliary contact. The safety contacts are rated for 5A at 250V AC under AC-15 utilization category and 6A at 24V DC under DC-13. Built-in contact fuse protection is provided with 4A time-delay (T) and 6A fast-acting (F) ratings. The device supports both manually monitored and automatic reset modes, configurable via external wiring. It features short-circuit detection across input contacts and real-time operational status monitoring. LED indicators on the front panel provide clear visual feedback for power supply and channel 1/2 status. The number of available safety contacts can be increased by connecting expansion modules.

Installation is designed for simplicity and reliability. The SR4P3A1B24 mounts on standard 35mm DIN rails using plug-in spring terminals (cage clamp style) for secure and maintenance-friendly wiring. The compact housing measures 96mm in length, 22.5mm in width, and 116mm in height, with a weight of 330g. The device accommodates conductor cross-sections from 0.2mm² to 2.5mm² and supports cable lengths up to 100 meters. It operates on a 24V DC or 24V AC supply with a voltage tolerance of 85-110%, consuming 3W of power. The SR4P3A1B24 is rated IP50 and functions reliably in ambient temperatures from -10°C to +55°C, with storage capability from -40°C to +85°C. Response times include a release buffer time under 15ms, automatic reset time of 35ms, and manual reset time of 30ms.

The SR4P3A1B24 complies with a comprehensive suite of international standards, including EN 60947-5-1 for control circuit devices, EN 61000-6-2 and EN 61000-6-3 for electromagnetic compatibility, IEC/EN 60204-1 for electrical equipment of machines, EN ISO 13849-1 for safety-related parts of control systems, and EN60068-2-6 for vibration resistance. It is an ideal safety monitoring solution for press equipment, packaging machinery, robotic work cells, and automated production lines requiring certified protection of operators and equipment.

Technical Specifications