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Characteristic elements Selection criteria Determination of the safety distance Muting Function Blanking Function
PHOTOELECTRIC SAFETY LIGHT CURTAINS
 SELECTION CRITERIA OF A SAFETY LIGHT CURTAIN
1.Definition of the zone to be protected.

2. Definition of the parts of the body to be detected:
- fingers or hands
- approaching body of a person
- presence of a person in a hazardous area

3. Definition of the safety distance between the light curtain and the hazardous point.

4. Definition of the safety category Level/Type to be adopted according to ISO 13849-1, IEC 62061, IEC 61496

Definition of the zone to be protected
• Take into account the configuration of the zone:
- shape and dimensions: width and height of the access area
- positions of hazardous parts
- possible access points
• The light curtain must be positioned so as to prevent the access to the dangerous area from above, from below, and from the sides without having intercepted the field protected by the light curtain.

It is possible to install one or more deflection mirrors in order to protect areas with access from several sides. This results in a considerable reduction in costs, as this solution eliminates the need of installing many separate light curtains.




DEFINITION OF TYPE OF DETECTION

  DETECTION CHARACTERISTICS ADVANTAGES
Finger
or
hand
 Detection necessary when
the operator must work
close to the danger.

Barrier resolution must be
less than or equal
to 40 mm.
 Possibility to lower the
dimensions by reducing at
the top the space between
the protection and the
dangerous zone.

Short time for machine
charging and discharging.

Less operator fatigue,
more productivity.
Body
(use as trip device)
 Ideal detection for access
control and protections of
several sides, also for long
scanning distances.

The barrier must be placed
at least at 850 mm from
the danger.

Barrier normally composed
by 2-3-4 beams.
 Protection costs reduced by the
restricted number of beams.

Possibility to protect zones
with big dimensions by using
deflection mirrors.

See note below
Presence
in a dangerous
zone
 Detection realized by
positioning the light curtains
horizontally to control
continuosly the presence
of an object in a
definite zone.
The light curtains resolution
depends on the height
of the detection plane,
anyway it cannot be
higher than 116 mm.
 Possibility to control
zones not visible from
where the machine’s push
button controls are
located.
 
Note: Accidental start-up of the machine shall not be possible when anyone crosses the sensitive area and stays undetected in the dangerous area.
Suitable ways of eliminating this type of risk include the following:
• Use of start / restart-interlock function positioning the command so that the dangerous area is in full view and so that the command cannot be
reached by anyone from inside the dangerous area
• The Restart command has to be safe in compliance with IEC 61496-1
• Use of additional presence sensing detectors for the detection of the operator inside dangerous area
• Use of obstacles preventing the operator from remaining undetected in the space between the sensing zone of the protective device and the
dangerous area.