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Complete Guide to EN ISO 13849-1: Functional Safety for Modern Machinery
time2025/11/21
- A comprehensive guide to EN ISO 13849-1, explaining how to assess machine risks, define required Performance Levels (PLr), and design safety-related control systems for compliance and reliability — ideal for manufacturers aiming for safe, standard-compliant automation.
Ensuring the safety of automated machinery is a core requirement in today's industrial environments. EN ISO 13849-1 is one of the most widely applied international standards for functional safety, providing a systematic framework for designing, evaluating, and validating safety-related control systems.
This guide explains the key principles of the standard, how Performance Levels are determined, and why compliance is essential for manufacturers, integrators, and end users.
What Is EN ISO 13849-1?
EN ISO 13849-1 is an internationally recognised standard that defines requirements for the design and assessment of safety-related parts of control systems. It applies to machinery across different industries, ensuring that safety functions are capable of reducing risks to acceptable levels.
The standard covers:
· The structure of safety-related control systems
· Hardware quality, diagnostics, and reliability
· Software design requirements
· Determining Performance Levels (PL)
· Validation of safety functions
Unlike older prescriptive standards, EN ISO 13849-1 takes a risk-based approach, allowing engineers to tailor safety solutions to the unique hazards of each machine.
The Role of Safety Functions
A safety function is any control action that helps prevent or mitigate a hazardous situation. Examples include:
· Emergency stop functions
· Guard monitoring on doors and fences
· Presence detection using safety light curtains or scanners
· Two-hand control units
· Safe speed or safe motion monitoring
Each function must be designed so that failures do not lead to unacceptable risk. EN ISO 13849-1 provides a structured method for evaluating the reliability of each function individually.
Understanding Performance Levels (PL)
Performance Levels (PLa–e) define how reliably a safety function must operate to reduce risk.
· PLa represents the lowest risk reduction capability
· PLe represents the highest
A PL rating depends on:
· Component reliability
· Architecture of the safety system
· Diagnostic coverage
· Resistance to common-cause failures
The higher the PL required, the stronger and more fault-tolerant the safety system must be.
How to Determine the Required Performance Level (PLr)
Determining PLr is a crucial step in early machine design. It ensures that engineers understand the reliability requirements of each safety function before selecting components or designing circuits.
PLr is defined by a risk assessment using three parameters:
1) Severity of Potential Injury (S)
· S1: Reversible or minor injury
· S2: Serious or irreversible injury, including death
2) Frequency and Duration of Exposure to the Hazard (F)
· F1: Low frequency or short exposure
· F2: Frequent or continuous exposure
3) Possibility of Avoiding or Limiting Harm (P)
· P1: Possible under certain conditions
· P2: Hardly possible to avoid once the hazard occurs
Using these three factors, engineers determine a required PLr (from PL a to PL e).
This PLr then guides the selection of system architecture, sensors, logic devices, and actuators capable of meeting the required reliability.
Designing Safety-Related Parts of Control Systems
After establishing PLr, engineers design the system to meet or exceed it.
EN ISO 13849-1 evaluates safety-related control systems based on:
System Architecture (Categories B, 1, 2, 3, 4)
Each category defines a different level of fault tolerance and monitoring.
MTTFd – Mean Time to Dangerous Failure
A measure of component reliability.
Diagnostic Coverage (DC)
How effectively dangerous failures are detected.
Common Cause Failure (CCF) Measures
Ensuring redundant components will not fail from the same cause.
A combination of these factors determines whether the safety function achieves the intended PL.
Software Requirements in EN ISO 13849-1
Software used in safety functions—whether embedded firmware or configurable safety controllers—must follow structured development principles.
Key requirements include:
· Defined specification and verification procedures
· Documentation and version control
· Measures to avoid systematic faults
· Testing and validation strategies
The standard emphasizes predictable and verifiable software behavior to prevent dangerous failures.
Validating the Safety System
Validation (as required by EN ISO 13849-2) ensures the final design meets the intended PLr.
This includes:
· Checking system architecture and reliability calculations
· Testing safety functions in real operating conditions
· Ensuring that all foreseeable failures have been addressed
Validation is essential not only for compliance but also for ensuring long-term safety performance.
Why Compliance with EN ISO 13849-1 Matters
Following the standard offers several key benefits:
· Regulatory compliance with machinery safety laws
· Improved workplace safety and reduced accident risk
· Reduced liability for manufacturers and integrators
· More reliable and predictable machinery performance
· Easier certification and market acceptance
In modern automation, functional safety is not optional—it is a competitive necessity.
Our Perspective: Delivering Dependable Safety Solutions
At Dadisick, we specialise in developing advanced industrial safety sensors and control technologies engineered to support high-performance level requirements.
Our solutions help machine builders and integrators create systems that balance safety with productivity, ensuring:
· Fast and accurate hazard detection
· Robust performance under demanding conditions
· Compliance with international safety standards
· Reliable achievement of required PLr values
By integrating high-quality sensing technologies, manufacturers can establish safer, more efficient environments with confidence.