In the world of advanced manufacturing and industrial automation, machine safety is non-negotiable. It protects personnel, prevents equipment damage, and ensures operational compliance. For anyone designing, implementing, or maintaining a control system, understanding the applicable safety standards is the foundation of their work.

These standards provide a common language and methodology for evaluating risk and designing control systems that fail safely. Here is an overview of the most critical international and regional standards and how they apply to your equipment.

The Foundation: Functional Safety Standards

The two main international standards for functional safety—which is safety that depends on the correct functioning of a system—are the IEC 61508 and ISO 13849 series.

1. IEC 61508: The Parent Standard (Electrotechnical)

This is often considered the parent standard for electrical, electronic, and programmable electronic (E/E/PE) safety-related systems.

  • What it does: It provides a comprehensive, systematic approach to functional safety. It governs the entire safety lifecycle, from initial concept and design through operation and eventual decommissioning.
  • Key Concept: Safety Integrity Level (SIL): IEC 61508 introduced the concept of SIL (Safety Integrity Level), which measures the probability that a safety function will fail to perform correctly when required. SIL is rated from 1 (lowest reliability) to 4 (highest reliability). Most industrial applications aim for SIL 2 or SIL 3.
  • Use Case: This standard is typically used when designing safety-related systems in process industries (like chemical or oil and gas) and is the basis for safety PLCs and components.

2. ISO 13849: Performance-Based Machine Safety (Machinery)

While IEC 61508 is broad, ISO 13849 (specifically Part 1, General principles for design) is the globally accepted standard for the safety of machinery.

  • What it does: It details how to design safety-related parts of control systems (SRP/CS) based on their ability to resist faults and achieve a necessary safety function.
  • Key Concept: Performance Level (PL): ISO 13849 introduced the PL (Performance Level), which ranges from ‘a’ (lowest) to ‘e’ (highest) and is required to meet the necessary risk reduction determined by a risk assessment. PL is calculated based on several factors, including:
    • Category: The structure of the safety circuit (how redundancy is used).
    • Mean Time to Dangerous Failure (): The reliability of the components.
    • Diagnostic Coverage (): How effective the system is at detecting its own faults.
    • Common Cause Failure (): Measures to prevent a single event from causing multiple safety functions to fail.
  • Use Case: This is the most common standard used by machine builders and system integrators worldwide when designing safety circuits for manufacturing, robotics, and assembly lines.

Regional and Application-Specific Standards

3. IEC 62061: Another Approach to Machinery (SIL-Based)

IEC 62061 is another machinery safety standard, similar in scope to ISO 13849, but it uses the SIL methodology derived from IEC 61508.

  • Key Difference: While ISO 13849 uses the letter-based PL rating, IEC 62061 uses the numerical SIL rating. Many designers today are comfortable using either PL or SIL for their machinery safety, as they often correlate (e.g., PL ‘e’ generally aligns with SIL 3).

4. ANSI B11 Series (North America)

In North America, the ANSI B11 standards, developed by the American National Standards Institute, provide application-specific guidance for various types of machinery (e.g., B11.19 for Performance Requirements for Safeguarding and B11.0 for general machine safety). These standards are often used in conjunction with the ISO/IEC standards to meet regional compliance.

Applying the Standards: A Simple 4-Step Process

Regardless of your industry, applying safety standards for a new or modified machine follows a consistent, systematic approach:

Step 1: Conduct a Mandatory Risk Assessment

This is the most critical starting point. Using a methodology like the one defined in ISO 12100 (a standard for general design principles), you must:

  1. Identify Hazards: What can cause harm (e.g., crushing, shearing, electrical)?
  2. Estimate Risk: Determine the severity of the potential injury, the frequency of exposure, and the probability of the hazard occurring.
  3. Determine Required Safety Performance: Based on the risk, you must choose the required Performance Level () or Required SIL for your safety functions. High-risk applications demand a higher PL ‘d’ or ‘e’ (or SIL 2/3).

Step 2: Design the Safety Function

Once you have the required PL or SIL, you design the specific safety function (e.g., an Emergency Stop circuit). You select components (e-stop buttons, safety relays, safety PLCs) that, when combined, meet the required performance level.

Step 3: Verify and Validate

This step confirms that the designed system actually achieves the required safety performance.

  • Verification (Calculation): You calculate the system’s achieved Performance Level (PL) using component data and the circuit’s architecture (Category). The calculated PL must be the required .
  • Validation (Testing): You physically test the installed system to ensure all safety devices and the safety logic operate correctly under all foreseeable conditions.

Step 4: Documentation

Maintain detailed documentation of the entire process, including the initial risk assessment, the safety design choices, component data, and the verification calculations. This documentation is essential for regulatory audit and compliance demonstration.

By following these internationally accepted standards, engineers move beyond simple checklists and adopt a rigorous, lifecycle-based approach to safety, ensuring that both productivity and protection are maximized on the industrial shop floor.