Safety Relay for Machinery Safety - Specifications and Verification

Product Specifications

Technical details and manufacturing context for Safety Relay

Definition

A safety relay is a critical component within a safety interlock circuit. It is responsible for monitoring the status of safety devices such as emergency stop buttons, safety gates, light curtains, or two-hand controls. When a safety device is triggered, the safety relay ensures the machine enters a safe state, typically by de-energizing power to hazardous functions, and prevents automatic restart until all safety conditions are manually reset. It is designed with redundant contacts, self-monitoring circuits, and forced-guided mechanisms to prevent failure modes that could compromise safety. This product is a component intended for integration into machinery control systems. It is not a standalone safety system and must be used in accordance with the manufacturer's instructions and applicable standards. The relay is available with a rated control supply voltage of 24 V DC, contact rating of 6 A (AC-15 at 230 V), and 3 normally open plus 1 normally closed safety contacts. Its response time is ≤30 ms, and it is suitable for safety functions up to SIL 3 per IEC 61508. Mechanical endurance is 10^7 operations, electrical endurance is 10^5 operations at rated contact current. Ambient operating temperature range is -25 to 55 °C, degree of protection is IP20, terminal type is screw (cage clamp optional), mounting is on 35 mm DIN rail, width is 22.5 mm, and approximate weight is 0.2 kg. All specifications are reference values and must be verified with the legal manufacturer for the specific model and application. Compliance with standards such as IEC 60947-5-1, IEC 61508, IEC 60529, and EN 60715 is a procurement reference and does not imply certification of this specific unit.

Working Principle

The safety relay operates by receiving input signals from safety devices. It continuously monitors these signals for faults such as short circuits, wire breaks, or contact welding. Using internal redundant and cross-monitored circuits, it processes the signals. If all inputs indicate a safe condition, it energizes its output contacts, allowing power to flow to the machine's control circuit. If any input indicates an unsafe condition or a fault is detected, it immediately de-energizes its outputs, cutting power to hazardous parts of the machine. Manual reset is typically required after a fault or safety device activation to restore operation.

Common Materials

Electrical Contacts (Silver Alloy), Coil (Copper Wire), Housing (Thermoplastic)

Technical Parameters

Parameter	Typical range	Notes & selection driver
Rated Control Supply Voltage	24 V DC	Other voltages available on requestIEC 60947-5-1
Contact Rating	6 A	AC-15 at 230 VIEC 60947-5-1
Number of Safety Contacts	3 NO + 1 NC	NO = normally open, NC = normally closed
Response Time	≤30 ms	Time from input signal to contact openingIEC 61508
Safety Integrity Level (SIL)	SIL 3	Suitable for safety functions up to PL eIEC 61508
Mechanical Endurance	10^7 operations	No load switchingIEC 60947-5-1
Electrical Endurance	10^5 operations	At rated contact currentIEC 60947-5-1
Ambient Operating Temperature	-25–55 °C	Non-condensing humidityIEC 60947-5-1
Degree of Protection	IP20	Terminals protected against finger contactIEC 60529
Terminal Type	Screw	Cage clamp optional
Mounting Type	35 mm DIN rail	Snap-on mountingEN 60715
Width	22.5 mm	Housing width
Weight	0.2 kg	Approximate

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Forced-Guided Contacts
Mechanically linked contacts that ensure if one contact welds shut, the opposing contact cannot close, maintaining a safe state.

Material: Silver Alloy, Thermoplastic
Monitoring Circuit
Internal electronic circuit that continuously checks for faults in the input signals and the relay's own operation.

Material: Printed Circuit Board, Electronic Components
Reset Circuit Part
Circuit requiring manual activation (via a reset button) to re-energize outputs after a safety shutdown or fault.

Material: Push Button, Electrical Contacts

Application & selection

Application Fit & Sizing Matrix

Operational Limits

voltage:	24V DC to 240V AC
temperature:	-20°C to +70°C
contact rating:	Up to 6A resistive load

Media Compatibility

✓ Dry industrial environments ✓ Control cabinets with IP20 protection ✓ Machinery with safety circuits

Unsuitable: High-vibration or explosive atmospheres without additional protection

Sizing Data Required

Safety Integrity Level (SIL) or Performance Level (PL) required
Number and type of safety devices to monitor
Electrical load characteristics (voltage, current, contact configuration)

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause

Contact Welding/Failure to Open

Cause: Electrical arcing due to high inrush currents, frequent switching under load, or contamination causing contacts to fuse together, preventing safe circuit interruption.

Coil Failure or Degradation

Cause: Overvoltage spikes, thermal stress from ambient heat or internal heating, or moisture ingress leading to insulation breakdown or open/short circuits in the coil winding.

Maintenance Indicators

Audible buzzing, chattering, or unusual humming from the relay enclosure during operation
Visual signs of overheating such as discoloration, melting, or burning on the relay housing or nearby wiring

Engineering Tips

Implement periodic contact resistance testing and infrared thermography during preventive maintenance to detect early signs of contact degradation or abnormal heating.
Ensure proper voltage regulation and use surge protection devices on the control circuit to prevent coil damage from electrical transients, and maintain a clean, cool, dry environment to reduce thermal and contamination stress.

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards

ISO 13849-1: Safety of machinery - Safety-related parts of control systems ANSI B11.19: Performance Requirements for Risk Reduction and Safeguarding IEC 61508: Functional safety of electrical/electronic/programmable electronic safety-related systems

Quoted from the published standard.

Manufacturing Precision

Contact gap: +/-0.05mm
Operating force: +/-10% of specified value

Quality Inspection

Dielectric strength test: 2500V AC for 1 minute
Functional safety test: Verification of forced-guided contacts and monitoring circuits

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

Compare the published product scope and source details, then include your specifications and quantity in an enquiry.

Manufacturers of Safety Relay

10 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Beijing Pinghe Entrepreneurship Technology Development Co., Ltd.

Beijing, CN

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