Unintentional 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
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.
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.
Detection type definition
|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,
(use as trip device)
|Ideal detection type for access control and protections of several sides, even for long
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
in a dangerous
|Detection realized by
positioning the light curtains horizontally to continuosly control 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.
Next ... Determination of the safety distance