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3SU12 compact units
7.2 Mounting
7.2.3
Front plate mounting, sensor switches
Systems designed for the installation and commissioning of the sensor switch must comply
with the requirements of EN 574 : 2008.
Prevention of accidental actuation and defeat. Please also read EN 574, Section 8.
The sensor switches for a two-hand control circuit must be arranged according to the risk
assessment for the individual application in such a way that the protective effect of the two-
hand control circuit cannot be defeated. The probability of accidental actuation must be
minimized. The use of a single hand, possible combinations of one hand and/or other parts
of the body and/or the use of simple aids which would allow the protective circuit to be
defeated must be taken into consideration so that there is no possibility that persons can
enter the hazard zone when hazards exist. Accidental actuation (e.g. by the operator's
clothing) must also be taken into account.
The following measures as defined by standard EN 574 : 2008 must be complied with:
● Prevention of protective circuit defeat by one hand
– Spatial separation between control actuating devices (clearance) of at least 26 mm
● Prevention of defeat by hand and elbow of the same arm
– Spatial separation between control actuating devices (clearance) of at least 550 mm
● Prevention of defeat by one hand and any other part of the body (e.g. knee, hip)
– Arrangement of control actuating devices on a horizontal surface at a distance of at
The sensor switches should not be installed in an exposed location (i.e. without operation
console or protective cover for switch) so as to prevent accidental actuation of the switch by
falling objects.
Safety distance (refer also to EN 574, Section 9.8)
The safety distance between the sensor switches and the hazard zone must be large
enough to ensure that the operator cannot enter the hazard zone after release of a sensor
switch until all potentially hazardous machinery has ceased moving.
The safety distance "S" in mm is calculated according to the following formula:
S = V x T + C
Key to formula:
V = Hand/arm speed = 1600 mm/s
T = Reaction time in seconds. The reaction time of the sensor switch is max. 50 ms)
C = Additional value = 250 mm
If entry of persons into the hazard zone following actuation of the sensor switch can be
reliably prevented, the additional value C can be set to "0".
However, the minimum clearance must always be 100 mm.
162
This clearance should not exceed 600 mm for ergonomic reasons
least 110 mm above the floor or the access level.
SIRIUS ACT 3SU1 pushbuttons and signaling devices
System Manual, 08/2018, A5E03457306020A/RS-AK/010
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