Machine Safety Shorts | Performance Levels
Performance Levels, also known as PL, are a crucial aspect of assessing the safety performance of safety-related control systems. In simple terms, Performance Levels indicate how well a safety system can reliably reduce risk and protect workers from potential hazards.
So, what is ISO 13849-1? ISO 13849-1 is an international standard developed by the International Organization for Standardization (ISO). It provides guidelines for the design and validation of safety-related control systems in machinery.
ISO 13849-1 offers a structured approach to evaluate the safety performance of safety-related parts of control systems, taking into account various factors that influence safety, such as the reliability of components and the overall design of the system.
The standard defines five levels of Performance (PL) - PL a, b, c, d, and e - with PL e being the highest level of performance and PL a being the lowest. The selection of the appropriate Performance Level depends on the potential risk associated with the machine or equipment.
Now, let's dive deeper into the components that contribute to determining the Performance Level:
Severity of Injury: This considers the potential severity of harm to a person if an accident occurs, ranging from minor injuries to fatal consequences.
Frequency and Duration of Exposure: It takes into account how often workers are exposed to the hazards and the duration of that exposure.
Possibility of Avoidance: This factor assesses the likelihood of avoiding the hazard when it arises.
Possibility of Defeat: It evaluates the likelihood of workers intentionally defeating or bypassing the safety measures.
Evaluating these factors helps to establish the necessary level of risk reduction required from the safety system. The higher the risk, the higher the required Performance Level to ensure adequate protection.
ISO 13849-1 also provides guidance on the calculation of the Performance Level, taking into consideration various aspects, such as Mean Time to Dangerous Failure (MTTFd) and Diagnostic Coverage (DC).
MTTFd refers to the average time it takes for a safety-related part of the control system to fail dangerously. A higher MTTFd indicates a more reliable system.
On the other hand, Diagnostic Coverage (DC) measures the effectiveness of the safety-related control system in detecting potential faults. A higher DC means that the system can detect and respond to faults more reliably.
By calculating MTTFd and DC, engineers can determine the achieved Performance Level and compare it to the required Performance Level to ensure compliance with ISO 13849-1.
Implementing ISO 13849-1 and achieving the appropriate Performance Level can greatly enhance workplace safety. Employers, equipment manufacturers, and safety professionals must collaborate to ensure the safety systems are correctly designed, validated, and maintained.