Safety Relays

Part Number	Description / PDF	Quantity
SFS3-DC24V Panasonic	RELAY SAFETY 4PST 6A 24V	12
SFS4-L-DC24V-D Panasonic	RELAY SAFETY 6PST 6A 24V	219
SFY2-DC21V Panasonic	RELAY SAFETY 4PST 6A 21V	0
SF4D-DC5V Panasonic	RELAY SAFETY 8PST 6A 5V	54
SFS6-DC48V Panasonic	RELAY SAFETY 6PST 6A 48V	0
SFS4-DC12V Panasonic	RELAY SAFETY 6PST 6A 12V	397
SFS3-L-DC48V-D Panasonic	RELAY SAFETY 4PST 6A 48V	0
ASFM0035S Panasonic	RELAY SAFETY DPST NO/NC 6A/3A 3V	0
ASFM0242S Panasonic	RELAY SAFETY DPST NONC 6A/3A 24V	0
SFS5-L-DC24V Panasonic	RELAY SAFETY 6PST 6A 24V	0
ASFM0212X Panasonic	RELAY SAFETY DPST NONC 6A/3A 21V	0
ASFM0032X Panasonic	RELAY SAFETY DPST NO/NC 6A/3A 3V	0
SF2D-DC48V Panasonic	RELAY SAFETY 4PST 6A 48V	0
SF2D-DC24V Panasonic	RELAY SAFETY 4PST 6A 24V	283
SFS2-DC12V Panasonic	RELAY SAFETY 4PST 6A 12V	0
ASFM0122S Panasonic	RELAY SAFETY DPST NONC 6A/3A 12V	0
SFS2-L-DC48V-D Panasonic	RELAY SAFETY 4PST 6A 48V	38
SF4D-DC24V Panasonic	RELAY SAFETY 8PST 6A 24V	57
ASFM0212S Panasonic	RELAY SAFETY DPST NONC 6A/3A 21V	0
SFY3-DC18V Panasonic	RELAY SAFETY 4PST 6A 18V	0

Safety Relays

1. Overview

Safety relays are specialized control devices designed to ensure fail-safe operation in industrial systems. They monitor safety-related inputs (e.g., emergency stops, light curtains) and trigger protective actions by cutting power to machinery. Compliant with international standards like IEC 61508 and ISO 13849-1, these relays form the backbone of safety instrumented systems (SIS) across automation sectors.

2. Major Types and Functional Classification

Type	Functional Characteristics	Application Examples
Electromagnetic Safety Relays	Mechanical contact-based design with physical separation	Machinery emergency stops, simple safety circuits
Solid-State Safety Relays	Zero-contact semiconductor switching with vibration resistance	Precision equipment, explosive atmosphere environments
Programmable Safety Relays	Configurable logic with diagnostic capabilities	Robotic cells, complex safety interlocking systems
Monitoring Safety Relays	Continuous circuit integrity verification	Safety door interlocks, two-hand control systems

3. Structure and Components

Typical safety relay construction includes:

Enclosure: Flame-retardant polymer housing (UL94 V-0 rated)
Coil System: 24V DC/AC operating with bifilar winding for failure detection
Contact Arrangement: Gold-plated contacts with positive-guided mechanism
Diagnostic Circuitry: Built-in semiconductor for contact state monitoring
Mounting Options: DIN rail or PCB mount with screw/clamp terminal connections

4. Key Technical Parameters

Parameter	Typical Value	Importance
Safety Integrity Level (SIL)	SIL 3 (IEC 61508)	Determines risk reduction factor
Response Time	5-50 ms	Affects machine safe stop performance
Contact Rating	6A @ 250V AC	Dictates load switching capability
MTBF	500,000 hours	System uptime prediction
Environmental Temp	-20 C to +55 C	Operational reliability factor

5. Application Areas

Primary industries include:

Industrial Automation: CNC machines, assembly lines
Energy Systems: Wind turbine safety circuits
Transportation: Rail vehicle door control systems
Medical Equipment: MRI machine emergency cutoffs

Case Study: Automotive Press Line Safety

A major automotive manufacturer implemented safety relays in 1200-ton press machines, achieving PLc (EN ISO 13849-1) compliance through dual-channel emergency stop circuits with 35ms response time.

6. Leading Manufacturers and Products

Manufacturer	Representative Product	Key Features
Siemens	3SK1 Safety Relay	Modular design, PROFINET integration
Schneider Electric	XPSM Safety Relay	Multi-sensor monitoring, SIL3 capable
Omron	G9SP-N Safety Controller	Programmable with 30 pre-defined safety functions
Phoenix Contact	PSR-SCP-24DC-PO Safety Relay	Plug-in module with status visualization

7. Selection Guidelines

Critical selection factors:

Safety Category: Match to application risk assessment (Cat. 2/3/4)
Environmental Conditions: Consider temperature, vibration, and EMC
Certifications: Required standards (CE, UL, T V)
Expansion Capability: Future system scalability
Diagnostic Coverage: Minimum 90% recommended

8. Industry Trends

Emerging developments include:

Integration with Industry 4.0 through IO-Link interfaces
Functional safety for collaborative robots (cobots)
Wireless safety communication protocols
Miniaturization while maintaining IP67 ratings
AI-enhanced predictive maintenance capabilities