Did you know that the 2023/1230/EU regulation finally introduced a definition for safety functions, which was missing in previous versions of the Machinery Directive? Machine safety is the cornerstone of any manufacturing facility, and the new regulations not only standardize the approach but also set higher protection standards. In this article, we will explore what safety functions are, how standards regulate them, and how to practically implement them to ensure safe machine operation.
Table of Contents
What Are Safety Functions?
The 2023/1230/EU regulation introduces a definition for safety functions, which was previously absent in the Machinery Directive. According to the regulation:
“A safety function is a function of a protective measure designed to eliminate hazards or, if that is not possible, reduce risk, and whose faulty implementation can increase that risk.”
Why is this definition so crucial? A formal definition allows for a more precise risk assessment and the implementation of appropriate protective measures during the design and operation phases of machinery. Without a clear definition, manufacturers had to rely on general guidelines, which could lead to inconsistent solutions. Today, companies must identify and implement safety functions in detail according to the regulation’s requirements, which is essential for subsequent compliance assessments, such as those according to standards like PN-EN-ISO 13849-1 and PN-EN 62061.
How to Identify Safety Functions?
Identifying safety functions is a multi-step process. Standards like PN-EN-ISO 13849-1 and PN-EN 62061 offer different approaches to determine how protective functions should operate to reduce risk to an acceptable level.
Identifying Safety Functions According to PN-EN-ISO 13849-1
The PN-EN-ISO 13849-1 standard outlines the process of identifying safety functions in several steps:
- Risk Analysis: The first step involves a risk analysis, identifying all potential hazards associated with machine use. Each hazard must be described to determine which functions will be necessary to eliminate or minimize it.
- Determining Safety Functions: Based on the risk analysis, safety functions are determined to reduce risk to an acceptable level. An example might be an emergency stop that eliminates the threat of uncontrolled machine movement.
- Assigning Performance Level (PL): Each function must be assigned an appropriate Performance Level (PL). The PL level indicates the function’s ability to achieve the required risk reduction, ranging from PL a (lowest) to PL e (highest). This level depends on:
- Severity of Consequences (S) – the potential consequences of the hazard.
- Frequency or Duration of Exposure (F) – how often the operator is exposed to the hazard.
- Possibility of Avoiding the Hazard (P) – how easily the hazard can be avoided.
- Component Selection: The PL level determines which components are needed to implement the safety function. Components must meet requirements for reliability, diagnostics, and system architecture.
- Verification and Validation: At the end of the process, each function must be verified and validated to ensure it achieves the intended PL level and effectively reduces risk.
Identifying Safety Functions According to PN-EN 62061
The PN-EN 62061 standard focuses on the reliability of electrical, electronic, and programmable systems related to safety. This process involves:
- Risk Analysis: Similar to the ISO 13849-1 standard, the process begins with a risk analysis aimed at identifying hazards and determining safety requirements for each function.
- Determining Safety Functions: Functions related to controlling and monitoring key system components are determined. These may include state monitoring, fault detection, or emergency stop functions.
- Assigning Safety Integrity Level (SIL): Each safety function must be assigned an appropriate Safety Integrity Level (SIL), indicating the function’s reliability. SIL is classified from SIL 1 to SIL 4, with SIL 4 representing the highest reliability level. The SIL level depends on:
- Severity of Consequences (S) – potential consequences of the hazard.
- Frequency of Exposure (F) – how often the operator is exposed to the hazard.
- Possibility of Avoiding the Hazard (P) – how difficult it is to avoid the hazard.
- Selection of Technical Measures: Components and technologies are selected according to the SIL level to ensure the reliability of the function.
- Verification and Validation: After implementing the function, verification and validation are necessary to ensure the appropriate SIL level is achieved and the function operates as intended under real working conditions.
Examples of Safety Functions
Safety functions play a crucial role in protective systems. Here are some examples of functions used in the industry:
- Interlock Systems – prevent access to dangerous machine areas, such as a movable guard that stops the machine when opened.
- Two-Hand Control – requires both hands to operate the machine, preventing accidental contact with moving parts.
- Emergency Stop – a button that immediately halts machine operation.
- Light Curtains – optical barriers that detect human presence and automatically stop the machine.
- Presence Sensors – devices that detect the presence of an operator in hazardous zones.
- Overload Detection Systems – monitor machine operation and shut it down when a dangerous overload is detected.
Differences Between PL and SIL
The concepts of PL and SIL in machine safety standards allow for more precise assessment and classification. PL focuses on the reliability of control system components, analyzing their architecture and risk reduction capability. SIL refers to the reliability of the entire system, considering various aspects of design, implementation, and risk. PL is more oriented towards mechanical and electrical safety measures, while SIL is mainly applicable in programmable and electronic systems.
Importance of PL and SIL Standards in Practice
PL and SIL standards are crucial for automation integrators responsible for selecting appropriate protective measures. Applying these standards allows for a unified approach to safety and tailoring protection to specific application requirements. Using harmonized standards like PN-EN-ISO 13849-1 and PN-EN 62061 simplifies the machine compliance assessment process. For more complex machines or those with higher risk, it may be necessary to conduct an EU type examination or use other advanced forms of assessment.
Functions and their implementation according to PL and SIL standards are essential for ensuring worker protection and machine reliability. The formal introduction of the safety function definition into the regulation is a step towards uniform and effective safety solutions in the industry. Each safety function must be carefully planned, assessed, and implemented to meet standard requirements and ensure safety at every stage of machine use.
FAQ: Safety Functions
A safety function is a special function of a machine or system designed to eliminate hazards or reduce risk to an acceptable level. Its faulty operation can lead to increased risk.
These functions are essential for protecting machine operators and ensuring equipment reliability. They help avoid many potentially dangerous situations and ensure compliance with standards.
The key standards for these functions are PN-EN-ISO 13849-1, which focuses on Performance Level (PL), and PN-EN 62061, which defines Safety Integrity Level (SIL).
Identifying safety functions begins with a risk analysis. Then, the required functions are determined, and appropriate PL or SIL levels are assigned, followed by selecting components that will ensure their implementation.
Examples include emergency stops, light curtains, interlock systems, and two-hand controls. Each of these functions aims to minimize risk for the operator and those near the machine.