Rockwell Automation 2727-G7P20D3Q7 MobileView G750 Guard Machine Terminal - Manual (Page 22)

Publication 2727-UM002D-EN-P
2-4 Safety Precautions and Elements
• 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 3 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 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
!
• 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.