25 www.drivesncontrols.com June 2026 To close the safety gap, the standard limits the maximum permissible clearance next to the transported goods to 200mm. In realworld applications, however, passage gaps are often significantly larger, making it easy to bypass the protective device. This hazard can be eliminated using access protection with dynamic format adjustment (Fig 3). Here, two safety laser scanners generate a joint, closed, vertical protective field. In addition, distance sensors installed on both sides of the conveyor belt detect the position and width of the goods on the pallet – alternatively, this can also be determined using the scanners’ integrated measuring function. The safety system uses this information to release a corresponding area in the protective field, through which the transported goods can be conveyed without interruption. Access to the sides of the goods remains secured in accordance with standards. After the transported goods have passed through, the protective field is closed again automatically. If a person is walking or driving alongside them, this is also detected reliably. This innovative safety concept enables Performance Level d in accordance with EN ISO 13849-1. Hazard 3: Safety gap due to forklift truck muting In this example, two induction loops or ultrasonic sensors serve as muting function triggers. As soon as a forklift truck enters the sensor area, muting is initiated and the light barrier’s safety function is deactivated. The forklift can enter the station. This is no longer permitted under the new draft of DIN EN 415-4, because the hazard remains – a person could enter the danger zone assuming that the machine is in a safe state because the light curtain has been triggered, which is not the case during muting. This answer is to ensure that hazardous movements are always stopped when the light curtain’s protective field is interrupted. When the forklift leaves the danger zone, specially arranged induction loops generate a defined sequence that enables the system to restart automatically. If induction loops cannot be installed in the floor, the forklift's movement can be monitored using radar sensors. Both approaches meet functional safety requirements and prevent tampering. This also complies with PL d in accordance with EN ISO 13849-1. Limits of muting, and alternatives In summary, then, muting makes it possible to distinguish between transported objects and people, contributing to automation and efficiency. However, the process must always be protected against foreseeable incorrect operation and manipulation. Alternative safety approaches are especially necessary if muting sensors cannot detect transported objects reliably, or if large variations in object widths create gaps that are too wide alongside the transported goods. Muting on forklifts is no longer considered state-of-the-art in terms of safety technology. In all of these cases, hazardous areas remain potentially accessible and dangerous. Safe and standards-compliant techniques are available for these challenges. Leuze, for example, provides a structured development and testing process – from planning and programming to comprehensive validation and verification. The path to a safe installation begins with the requirement that automated operation must be reliable and safe. After conducting a thorough analysis with risk or hazard assessment, a safety designer can develop a concept and work out specific safety functions for the application. The appropriate hardware and sensors are then selected, integrated, programmed and tested. A dual control principle ensures functionally safe implementation. Comprehensive functional tests ensure that all safety and standard functions work reliably. Commissioning at a user’s site should take place only after successful validation under real operating conditions. The user then receives documentation, including a validation plan and CE declaration of conformity. n SAFETY n Fig 2: If distances are too great during muting, a person can enter the danger zone unnoticed alongside the transported goods. Fig 1: meshed containers or other objects that are difficult for muting sensors to detect are often fed onto or discharged from pallets Fig 3: In access guarding with dynamic format adaptation, two safety laser scanners generate a joint, closed vertical protective field
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