How do I calculate the correct safety distance between the hazard and the location of the light curtain?
For the U.S., the safety distance is typically calculated using OSHAs suggested formula: Ds = Hs x (Ts+Tp+Tr+2Tm) Dp Where: Ds = Minimum safety distance (in inches). Hs = Hand Speed constant of 63 inches per second (1.6 m/s). Ts = Maximum machine stopping time (in seconds). Tp = Maximum response time of the light curtain (in seconds). Tr = Maximum response time of all other interposing control elements e.g. safety controller, motor contactor, safety PLC (in seconds). Tm = Increase in the press stopping time allowing for brake wear (in seconds). Dp = Penetration depth factor (using the OSHA Penetration Depth Factor Calculation chart or formula) In addition ANSI (American National Standards Institute) has established a formula that will result in a similar calculation. In Europe, the following formula (adopted from EN 999) should be used and documented in the technical file: S = K (t1+t2+t3) +C Where S = minimum safety distance (mm) K = approach speed of object to the hazard (mm/sec) t1
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