Programmable Safety Controller SCR P
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Corner Mirrors, Optical Safety Systems, and Muting
Mirrors are typically used with safety light screens and single-/multiple-beam safety systems to guard multiple sides of a
hazardous area. If the safety light screen is muted, the safeguarding function is suspended on all sides. It must not be
possible for an individual to enter the guarded area without being detected and a stop command issued to the machine
control. This supplemental safeguarding is normally provided by an additional device(s) that remains active while the
Primary Safeguard is muted. Therefore, mirrors are typically not allowed for muting applications.
Multiple Presence-Sensing Safety Devices
Muting multiple presence-sensing safety devices (PSSDs) or a PSSD with multiple sensing fields is not recommended
unless it is not possible for an individual to enter the guarded area without being detected and a stop command issued to
the machine control. As with the use of corner mirrors (see
Corner Mirrors, Optical Safety Systems, and Muting
multiple sensing fields are muted, the possibility exists that personnel could move through a muted area or access point to
enter the safeguarded area without being detected.
For example, in an entry/exit application where a pallet initiates the mute cycle by entering a cell, if both the entry and the
exit PSSDs are muted, it may be possible for an indivi
dual to access the guarded area through the “exit” of the cell. An
appropriate solution would be to mute the entry and the exit with separate safeguarding devices.
Two-Hand Control Block
The TC input can be mapped directly to an output or to a logic block. The Two-Hand Control function block can be mapped
directly to an output or to a logic block.
If the machine has multiple operators and each operator must actuate their two-hand controls, use the Two-Hand Control
function block in which multiple TC inputs can be selected.
If the system has a hold function (TC inputs causing an action that makes it safe, then the operators can remove their hands
while the process finishes), use the Two-Hand Control function block with the Muting function selected.
If the machine has certain safety devices that should be satisfied (and must stay satisfied) for the TC input to make the
machine operate, use the Two-Hand Control function block with the IN node selected.
• If the IN node is off, engaging the Two-Hand input results in no actions.
• If the Two-Hand Control function block is on and the TC block goes off, the output turns off.
• When the IN node goes back high, the output stays off until the TC inputs goes off and back high.
WARNING: Guarding Multiple Areas
Do not safeguard multiple areas with mirrors or multiple sensing fields, if personnel can enter the
hazardous area while the System is muted, and not be detected by supplemental safeguarding that will
issue a stop command to the machine.
WARNING:
• Two-Hand Controls are starting devices (initiate hazardous motion).
• Failure to follow these instructions could result in serious injury or death.
• The Qualified Individual must ensure that activation (going to the ON condition) of a stopping
safety device (E-Stop, Rope Pull, Optical Sensor, Safety Mat, Protective Stop, etc.) by a user
does not initiate hazardous motion when logically connected to a TC Input or Two-Hand Control
function block that is already activated (ON condition).
