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, page 41). 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 deviceHeight of the beams above reference plane
4300, 600, 900, 1200 mm
3300, 700, 1100 mm
2400, 900 mm

It is possible to pass under beams over 300 mm or pass over beams under 900 mm.