FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY
sponsored by DESIGNING FOR SAFETY: IMPLEMENTING
SAFE CONTROL SYSTEMS (PART 2) Ensuring machinery safety requires more than just selecting the right
components – it demands a structured design process that guarantees reliability in safety-related control systems, as EUCHNER explains
assessment in accordance with BS EN ISO 12100. This process helps identify hazards and determine whether they can be eliminated through design modifications. Where risks cannot be removed entirely or reduced to an acceptable level, a control safeguard must be implemented. Once safeguards are identified, the required
T
Performance Level (PLr) is defined using BS EN ISO 13849-1, ensuring the selected control measures align with the severity of the identified hazards. From here, engineers can select and integrate the appropriate safety components, such as interlocks, light curtains, or emergency stop devices. Finally, to ensure compliance, the control system is verified using tools such as SISTEMA, which confirms that the required Performance Level (PL) has been achieved. By following this structured approach, engineers can design control systems that comply with safety regulations but also enhance machine reliability and operational efficiency.
FROM RISK ASSESSMENT TO SAFETY CONTROL The foundation of any safe control system lies in the risk assessment process. The objective is to eliminate risks through design wherever possible, but when that is not feasible, a safety-related control function must be introduced. A crucial step is defining the appropriate
Performance Level (PLr). BS EN ISO 13849-1 categorises safety control functions into five Performance Levels (PLa to PLe), with PLe representing the highest integrity level. The more severe and likely the hazard, the higher the PLr required. Engineers must ensure that the control system meets this defined level of integrity by choosing reliable safety components. This risk-based approach provides an optimised balance between safety and efficiency, ensuring compliance without unnecessary complexity or cost.
SELECTING SAFETY COMPONENTS Once the PLr has been determined, the control system must be designed using components that can achieve the required level of safety performance. The effectiveness of a safety- related control system depends heavily on the selection and integration of appropriate components, which include interlocking devices, emergency stop functions, and presence-sensing systems like light curtains. When selecting interlocks, for example, it is
essential to consider factors such as reliability, resistance to manipulation, and diagnostic
22 DESIGN SOLUTIONS APRIL 2025
capability. In high-risk applications, RFID-based interlocks provide a greater level of security than traditional mechanical interlocks. Manufacturers such as EUCHNER provide
comprehensive performance data for their safety components. By choosing products from established suppliers with deep expertise in machinery safeguarding, engineers can ensure that their control system meets the required safety performance levels. Beyond selecting the right components, engineers must also consider Diagnostic Coverage (DC) and Common Cause Failure (CCF), as these factors play a significant role in achieving the required Performance Level (PL).
DIAGNOSTIC COVERAGE (DC) Diagnostic Coverage (DC) refers to a system’s ability to detect faults and prevent unsafe failures. A higher level of DC ensures that potential failures are identified before they lead to hazardous situations, making it a critical factor in achieving a high Performance Level (PL). For example, an electronic interlock with built-
in monitoring, such as the EUCHNER CTS, offers a high level of DC. These devices can detect faults and provide real-time feedback, ensuring that failures are identified before they compromise safety. In contrast, a mechanical interlock without monitoring capabilities may provide low DC, meaning that failures could go undetected. Integrating self-monitoring safety devices into
the control system improves reliability, simplifies maintenance, and ensures that faults are addressed before they escalate into serious risks.
ADDRESSING CCF Designing redundant safety systems presents challenges beyond hardware selection, particularly the risk of Common Cause Failure (CCF) – where multiple safety channels fail due to a shared influencing factor. Unlike random hardware failures, CCF can compromise the entire safety function. Several factors contribute to CCF, including
dust, moisture, or vibration, which can degrade multiple components simultaneously. Electrical
o create an effective safety-related control circuit, engineers must follow a methodical approach that begins with conducting a risk
interference, such as electromagnetic disturbances or poor grounding, may also affect redundant safety circuits at the same time. Using identical sensors or interlocks for redundancy without considering diverse failure modes increases the likelihood of a shared failure. To reduce the impact of CCF, engineers must
incorporate design diversity, such as using different sensor technologies for redundant safety functions. Physical separation of redundant components can also prevent simultaneous failures due to environmental exposure. The BS EN ISO 13849-1 standard provides a structured assessment for CCF resistance, ensuring that safety systems remain robust and reliable.
VERIFICATION & TRAINING Once the safety-related control system is designed, verification is essential to confirm compliance. The SISTEMA software tool provides an efficient way to calculate the achieved Performance Level (PL) based on the selected hardware and system architecture. By analysing control system redundancy, failure rates, diagnostic coverage, and CCF resistance, SISTEMA ensures that the system meets safety requirements before final implementation. However, designing a safety-related control
system also demands specialist knowledge. With safety technologies evolving and regulations tightening, engineers must stay up to date with the latest methodologies and best practices. Industry leaders such as EUCHNER offer expert
training programs, equipping engineers with the skills to design, validate, and implement fully compliant safety control systems. By working with experienced suppliers and staying informed about emerging safety technologies, engineers can develop machinery that is not only compliant but also highly efficient and future-proofed. Achieving a safe machine control circuit
requires a structured approach, starting with risk assessment and defining the appropriate Performance Level (PLr). Selecting high- reliability safety components, considering Diagnostic Coverage (DC) and Common Cause Failure (CCF), and verifying the system using SISTEMA, all play a vital role in ensuring that safety functions operate as intended. By choosing proven safety technologies
and working with knowledgeable suppliers, engineers can design machinery that meets compliance standards while improving efficiency, reliability, and workplace safety.
EUCHNER (UK) T: 0114 2560123
www.euchner.co.uk
Feature
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
