Door Industry Journal - Winter 2020

Also online at: www.dijonline.co.uk 96 THE door industry journal winter 2020 Automated Gates & Barriers Understanding the ‘Swept Area’ of a Hinged Powered Gate The ‘swept area’ of a hinged powered gate, or indeed industrial door, continues to generate high numbers of enquiries to the dhf technical and training department. Whilst most people understand safety at the leading edge (the vertical edge where the gates meet or where a single leaf meets its closing post), the swept area seems to be less understood. dhf ’s Training and Compliance Officer, Nick Perkins, offers expert guidance on the safety of hinged gates and doors. “It is clear that an element of confusion stems from the fact that hinged gates and doors are force tested at the leading edge, leading some to consider that the leading edge is the only part that needs to be safe. Nothing could be further from the truth,” explains Nick. “In fact, as a result of the dynamics involved, the leading edge will be subject to the least torque, whilst the hinge area generates the most. Of course, ultimate force (as opposed to torque) is affected by a combination of weight, speed, torque and stopping distance (overtravel). As speed of travel is highest at the leading edge and lowest at the hinge, speed and torque do, to some degree, counter each other.” The greatest potential for harm actually exists closer to the hinge, particularly where there is a crush potential. Crush potential in the swept area can be caused by the gap under the leaf (foot crush potential), the shape of the gap under the leaf (crush potential caused by, for example, slopes and kerbs), the proximity of static objects (for example, walls, fences and bollards) and the design of the hinge, reducing gaps at the hinge being particularly lethal. In addition to crush potential, the entire swept area of a hinged gate or door generates a significant impact hazard, not just at the leading edge. The applicable standard for powered vehicle gates and doors is BS EN 12453, which has been in existence for approximately 20 years. It requires that all crush and impact hazards must be controlled using either hold-to-run, force limitation or non-contact presence detection as follows: • Hold-to-run requires that all hazards being protected are clearly visible to the operator at the control station. • Force limitation requires that a force of 25N is acceptable indefinitely, a force between 25N and 150N can only exist for a maximum of five seconds, and any force greater than 150N can only exist for a maximum of 0.75 of a second. The standard goes on to set a limit of 400N in crush areas (reducing gaps less than 500mm) and 1400N in impact areas (reducing gaps greater than 500mm). To achieve this, given the lower force and time limits, the leaf will need to stop and reverse on contact. • Non-contact presence detection requires that contact with the hazard causing movement must be prevented completely. In order to achieve this for a hinged system, the protective device (typically some form of optical scanner) will need to be mounted on the leaf and move with it; this is borne out by the required test methods. “In all cases, it is evident that the protection in use must be effective in the entire swept area and in both directions of travel,” concludes Nick. “DHF TS 011:2019 (gates) and TS 012:2019 (vehicle doors) provide the required detail, with both documents available on the dhf website: https://www.dhfonline.org.uk/publications/technical-specifications/1.htm ” Have you liked our facebook page yet? We post news everyday! www.facebook.com/DoorIndustryJournal