Door Industry Journal - Summer 2016

Also online at: www.dijonline.co.uk industry news feature 7 THE door industry journal summer 2016 rapidly reducing towards the hinge area. These two factors are largely mitigated by each other across the width. This relationship does though generally go astray in the last 10% of leaf width and hence extra precautions must be taken at the hinge area. Testing at the leading edge (point of greatest speed) does give a workable indication of force across the gate when using inherent or safe edge derived force limitation. Other means of verification must be used at the hinge area to ensure that forces are safe at all exposed moving interfaces and reducing gaps. (The DHF Powered Gate Safety Diploma offers practical advice and guidance on this last point.) Myth 4: Force limitation is not required where a horizontal photo beams are in use A horizontal photo beam never has been, and is not, sufficient as a safety device. They have only ever been specified by any applicable standard (EN 12453) as an enhancement to active and sufficient force limitation where automatic operation (auto close) is in use or where untrained persons might encounter the door, gate or barrier (most installations). This is because a photo beam is far too easy to defeat by standing astride, leaning or reaching over the beam. Horizontal photo beams can only alter the probability of contact; a safety device (e.g. force limitation) provides the required control of the possibility of injury. As an alternative to force limitation, light curtains and photo scanners can be used to protect hazardous areas of powered industrial doors, garage doors, gates and traffic barriers. These specialised devices should not be confused with photo beams. Light curtain and photo scanner technology prevents all access to any hazardous movement by setting up a complete and comprehensive light screen across the entire accessible hazard area that cannot be defeated or bypassed. They must also be tested to verify effectiveness, not with a force meter but the appropriate test piece as specified by EN 12445. In summary Where force limitation is used to control hazards on powered industrial doors, garage doors, gates and traffic barriers, verification that safe forces are achieved will be needed, either by testing on site with an EN 12445 compliant test meter, or by the presence of documentary evidence that an EC approved notified test laboratory has conducted the required testing, or that the manufacturer has asserted that further testing (beyond their own type testing) is not needed as part of the commissioning process in the installation instructions. Force measurement with an EN 12445 compliant test meter is the only way to verify that safe force levels still exists as part of maintenance or modification activities. The specification for an EN 12445 test meter is: • Two contact areas with a diameter of 80 mm +/- 1% • The contact areas shall be made of suitable material and be of sufficient thickness to retain rigidity • A spring which gives the contact area a spring ratio of 500 N/mm +/- 50 N/mm • Measuring range from 25 N to 2000 N • Rising/falling time of the load cell amplifier not > 5ms The equipment shall be calibrated annually and therefore be able to give measured values with an accuracy of at least +/- 5 % or +/- 10 N, whichever is the maximum deviation. For more information about force testers see Microtronics article on page 86. © Image courtesy of Hörmann. © Image courtesy of Microtronics Srl