Allen-Bradley Guardmaster, User Manual

Page: 23 / 100

Rockwell Automation Publication 440R-UM013E-EN-P - March 2017 23
Power, Ground, and Wire Chapter 3
From the perspective of the GSR relay, only the OSSD device closest to the
relay (Device 3 in Figure 11 ) is of concern. The other devices with OSSD
outputs do not affect the performance of the safety relay. The EM Devices can
suffer from masked faults, their safety rating is limited to Category 3 per
ISO13849-1.
Figure 11 - Example Connections to Device with Cascaded and Non-cascaded OSSD Devices
GSR relays cannot detect short circuits of the OSSD device outputs. The
PWR/Fault status indicator of your GSR relay remains solid green. The device
with the OSSD outputs must detect short circuits of its own OSSD outputs.
When detected, the device must shut off both OSSD outputs and go to a
faulted state. A status indicator must inform you that the OSSD device is
faulted.
Safety Mats
Guardmaster (and similar) safety mats can be connected to safety relays. These
mats use parallel metal-plate technology. Stepping on the mat shorts the top
metal plate to the bottom metal plate. With the proper connections, safety
relays detect the presence of an object on the mat and turn off their outputs.
With no presence on the mat, safety relays turn on their outputs.
When changing the function from mechanical switches or OSSDs to safety
mats, GSR relays must go through the complete configuration process.
Figure 12 on page 24 shows the typical connections for safety mats. You notice
the reverse of the wiring between a device with 2 N.C. contacts and the safety
mat.
When a safety mat is used, safety relays cannot detect short circuits between
the inputs or between the inputs and 24V DC. These conditions must be
tested during validation.
DI and DIS
A2
Device 5 Device 6
S12
A1
A2
A1
A2
Input 2 Input 1
S22 S32 S42
CI and SI
A1
A2
A1 S12
Input 1
S22
+24V DC
24V Com
Device 5
A1
A2
Device 3 Device 4
A1
A2
A1
A2
Device 3
A1
A2
Device 1 Device 2
A1
A2
A1
A2
Device 1
A1
A2