Calculation formula for the minimum safety distance of multiple light beam safety devices for access guarding:

If the risk assessment determines that a detection of the penetration of the entire body is sufficient, the following calculation formula must be applied (see also, fig. 4.2.1-6). The additional 850 mm to be added on corresponds with the arm length:

Ds = Hs x (Ts + Tc + Tr + Tbm) + DH

DH = 850 mm



This type of arrangement of the protective device allows an operator to be between the sensor and the point of operation without being detected after crossing the protective device. A start/restart interlock function that prevents the machine from starting is provided in every case. The command device (reset button) must be positioned so that the entire danger zone can be seen and it cannot be operated from the danger zone.

With the risk assessment and selection of the appropriate protective device, a possible getting around, e.g. crawling under the lowest beam, reaching over the highest beam, reaching through or climbing through two beams must be taken into account.

Number of beams of the protective device Height of the beams above reference plane
4 300, 600, 900, 1200 mm
3 300, 700, 1100 mm
2 400, 900 mm



Beams that are more than 300 mm high can be crept over and beams that are less than 900 mm can be stepped over.