Safety relay from Metz Connect

Standards and Directives for Safety Relays

The selection and use of safety switching devices is clearly governed by international standards and EU directives.

ISO 13849-1 – Performance Level Defines requirements for safety-related parts of control systems (SRP/CS). The standard specifies 5 Performance Levels (PL a to PL e) and describes how to calculate them using category, MTTF, DC and CCF. The primary standard for machine builders in the EU.		IEC 62061 – Safety Integrity Level Standard for safety-related electrical control systems in industry. Assesses safety functions via Safety Integrity Level (SIL 1 to 3) based on PFH values (probability of dangerous failure per hour). Used alongside or as an alternative to ISO 13849.		EN 60947-5-1 – Low-Voltage Switchgear Product standard for electromechanical control devices. Governs technical requirements for control and signalling circuits, switching devices and positively guided contacts. Basis for CE marking of safety relays.
Machinery Directive 2006/42/EC EU directive establishing essential health and safety requirements for machinery. Safety relays are frequently part of the evidence for the declaration of conformity. From 2027 it will be replaced by the Machinery Regulation (EU) 2023/1230.		IEC 61810-3 – Positively Guided Contacts Defines requirements for electromechanical elementary relays with positively guided contacts. The positive guidance ensures that NC and NO contacts can never be closed simultaneously – the fundamental principle of relay safety.		EN 574 – Two-Hand Controls Safety standard specifically for two-hand controls. Defines three types (I, II, III) with different levels of protection. Type III C (simultaneous actuation, anti-defeat) is the highest level and is required for presses and stamping machines.

Performance Level vs. Safety Integrity Level

Both metrics describe the ability of a safety function to prevent a dangerous failure – calculated according to different standards.

PL (ISO 13849)	SIL (IEC 62061)	PFH Range (failures/h)	Typical Application
PL a	–	≥ 10⁻⁵ to < 10⁻⁴	Simple guards, low risk categories
PL b	SIL 1	≥ 10⁻⁶ to < 10⁻⁵	Simple guards, minor injury risk
PL c	SIL 1	≥ 10⁻⁷ to < 10⁻⁶	Safety gates, simple guard rails, medium risks
PL d	SIL 2	≥ 10⁻⁸ to < 10⁻⁷	Emergency stop, interlocked safety gates, light curtains
PL e	SIL 3	≥ 10⁻⁹ to < 10⁻⁸	Highest requirements: presses, robot cells, ATEX zones

Single-Channel vs. Dual-Channel Evaluation

The number of channels is decisive for the achievable Performance Level and fault tolerance of the safety function.

► Single-Channel Evaluation (Category B, 1, 2) ✓ For lower safety requirements (PL a to PL c) ✓ One input signal is monitored ✓ No protection against cable break or short circuit at the sensor ✓ Suitable for simple guards and safety mats (low risks)

⚠ Dual-Channel Evaluation (Category 3, 4) ✓ For high safety requirements (PL d, PL e) ✓ Two independent input signals are evaluated redundantly ✓ Integrated cross-circuit detection and wire break monitoring ✓ Mandatory for emergency stop, interlocked guards, light curtains at robot cells

Related Categories in the Shop

Further products from the Industrial Relays and Contactors range at Industry-Electronics.

► Industrial Relays Standard switching relays and coupling relays for general switching tasks in automation and control engineering.		► Industrial Timing Relays Timing relays for start-up delays, run-down functions and cyclic control tasks in automation technology.		► Contactors Power contactors and motor protection switches for safe switching of drives, motors and loads up into the kW range.
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⚠ Safety Relay Technical Support Uncertain about which safety relay is right for your application? Our technical team advises on device selection, Performance Level, wiring concepts and standards compliance – personally and without detours. +49 (0)7666 / 88499-0  |  sales@industry-electronics.com