Improper E-Stop Control
NOT RECOMMENDED
The configuration top right shows OS1 and
E-Stop button ES1 with a Latch Reset LR1
connected to a mute function via the AND
function. In this case both ES1 and OS1 will
be muted.
If there is an active mute cycle in progress
and the E-Stop button is pressed (switched
to the Stop state), SO1 will not turn Off. This
will result in a loss of safety control and may
lead to a potential hazardous condition.
Proper E-Stop Control
The configuration to the right shows OS1
connected directly to the Mute block M1. M1
and ES1 are both inputs to AND A1. In this
case both M1 and ES1 control SO1.
If there is a an active mute cycle in progress
and the E-Stop button is pressed (switched
to the Stop state), SO1 will turn Off.
E-Stop Button control authority when using the Mute function
!
WARNING
Figure 76. Emergency Stop and Mute Function
E-stop buttons, rope pulls, enabling devices, external device monitoring, and bypass switches are non-mutable devices or
functions.
To mute the primary safeguard appropriately, the design of a muting system must:
1. Identify the non-hazardous portion of the machine cycle.
2. Involve the selection of the proper muting devices.
3. Include proper mounting and installation of those devices.
WARNING:
• Use Mute and Bypass operations in a way that minimizes personnel risk.
• Failure to follow these rules could cause an unsafe condition that could result in serious injury or
death.
• Guard against unintended stop signal suspension by using one or more diverse-redundant mute
sensor pairs or a dual channel key-secured bypass switch.
• Set reasonable time limits for the mute and bypass functions.
The Safety Controller can monitor and respond to redundant signals that initiate the mute. The mute then suspends the
safeguarding function by ignoring the state of the input device to which the muting function has been assigned. This allows
an object or person to pass through the defined area of a safety light screen without generating a stop command. This
should not be confused with blanking, which disables one or more beams in a safety light screen, resulting in larger
resolution.
The mute function may be triggered by a variety of external devices. This feature provides a variety of options to design the
system to meet the requirements of a specific application.
A pair of muting devices must be triggered simultaneously (within 3 seconds of one another). This reduces the chance of
common mode failures or defeat. Directional muting, in which sensor pair 1 is required to be blocked first, also may reduce
the possibility of defeat.
At least two mute sensors are required for each muting operation. The muting typically occurs 100 ms after the second
mute sensor input has been satisfied. One or two pairs of mute sensors can be mapped to one or more safety input devices
so that their assigned safety outputs can remain On to complete the operation.
XS/SC26-2 and SC10-2 Safety Controllers
92
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