Rockwell Automation Allen-Bradley MobileView Guard G750 Démarrage Rapide page 8

8 MobileView Guard G750
• In special operating mode, safety must be guaranteed in other ways since the
operator must enter dangerous areas of the machine, and targeted
movements must be possible. In this case, a reduced speed of the machine
must be defined by means of the risk assessment. A movement will only be
possible if an enabling device is actuated. The user must be trained and
must know the details of the intended use. The safety related parts of the
control for reducing speed and for the enabling device must be constructed
so that they meet the safety category according to EN 954-1, defined by the
risk assessment.
To meet safety category 3 in accordance with EN 954-1, the enabling switch must
be implemented with 2 circuits.
EN 60204-1 describes the functioning of the enabling device. Due to the latest
findings of analysis of accidents and since technical solutions are available, the
3-position enabling switch became state of the art. The positions 1 and 3 of the
enabling switch are OFF functions. Only the central position is used for enabling.
The EN 60204-1 is identical with IEC 60204-1. So the 3-position enabling switch is
of international relevance.
The enabling switch consists of a 3-position operating element and separated
evaluation electronics. Essential features are the continuous two-channel circuits
between the actuating elements and the connecting terminals. For the evaluation
circuits, different technologies and circuits are used. Because of the electronic
switching contacts, their lifetime does not depend on the load as long as the
nominal values of the load (ohmic, inductive and capacitive) are not exceeded.
ATTENTION
!
Publication 2727-QS002E-MU-P
• Enabling switches may only be used if the operator
activating the switch recognizes the dangerous situation in
time to take immediate action if necessary.
• The enabling switch is only used to enable commands for
performing dangerous movements. The commands must
be activated by a separate operating element (key on
terminal). Only persons allowed to activate the enabling
switch are allowed to work in the dangerous area.
• On the MobileView Guard terminal, the enabling switches
always feature 2 circuits.