Safety
Presence Sensing Devices
Light Curtains
How to Calculate Safety Distances — U.S. Safety Distance Formulas
Safety Light Curtains must be mounted at a sufficient distance from the pinch point or point of operation hazard to ensure that the machine stops before a person’s hand(s), arm(s), or body reaches the hazard. This distance, referred to as the safety distance, must be properly calculated prior to determining the safety light curtain protective height and mounting the light curtains on the machine. Failure to properly calculate this safety distance may result in operator injury.
Note: Regardless of the calculated safety distance, Safety Light Curtains should never be mounted closer than 6 inches from the point of operation or pinch point hazard.
In the United States there are two formulas that are used to properly calculate the safety distance. The first, the OSHA formula, is the minimum requirement for the calculation of the safety distance. The second formula, the one recommended by Rockwell Automation, is the ANSI formula, which incorporates additional factors to be considered when calculating the safety distance.