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ApplicationSafety distanceEN 999Safety distances for lightcurtainsBetween the interruption of alight beam and the standstillof the machine, a certain timeexpires. The safety light gridor light curtain must be sizedand installed such that a stopwould be signalled and thehazard ceased prior to aperson or a body memberaccessing the hazard.The standard EN 999 providesthe user with detailedinformation about thecalculation of the minimumsafety distances. Theseinclude the followingimportant influencing factors:• run-out time of the entiresystem, taking the differentreaction times of theindividual systems intoaccount (e.g. machine,safety monitoring module,AOPD etc.)• capacity of the AOPD todetect body parts (fingers,hand and entire humanbody)• set-up of the safety guard innormal condition (verticalfitting), parallel condition(horizontal fitting) or at anarbitrary angle in front of thesafety guard and• the speed at which theprotection field isapproached.For the calculation of theminimum safety distance S tothe hazardous area, EN 999presents the following generalformula:S = K x T + CWhere:S the safety distance to thedanger point (mm)K the approach speed of thebody or the body part(mm/s)T the entire reaction time ofthe system(s)(including the machine’s runouttime, the reaction time ofthe safety guard and thesafety monitoring module etc.)C additional distance (mm) infront of the safety guardNormal approach for lightcurtains:(resolution: max. 40 mm)The minimum safety distanceS is calculated in the followingway:S = 2000 T + 8 (D-14)(D = resolution).This formula applies to safetydistances up to 500 mm.The minimum safety distanceSmin may not be less than100 mm.If the calculation produces adistance larger than 500 mmfor S, the calculation can berepeated with a lowerapproach speed:S = 1600 T + 8 (D-14)In this case, Smin may not beless than 500 mm.Light curtainApproachdirectionIf the danger point of themachine is accessible fromthe top because of itsparticular construction, theheight H of the topmost beamof the light barrier must be atleast 1800 mm above thebase G of the machine.Normal approach for lightcurtains:(resolution: from 40 mm upto max. 70mm)The minimum safety distanceS is calculated in the followingway:S = 1600 T + 850The height of the topmostlight beam must be at least900 mm, the height of thelowermost light beammaximum 300 mm abovethe bottom (for the protectionof children younger than14: 200 mm)Danger pointReference floor270