Banner SC22-3E Safety Controller with Ethernet - Manual (Page 108)

Category 2 E-Stop Circuit
A single-channel emergency stop application typically provides a
Category 2 level of circuit performance, because a short circuit
could cause the loss of the safety function. The principle of fault
exclusion must be incorporated into the design and installation to
either eliminate, or reduce to an acceptable (minimal) level of risk,
the possibility of undetected faults or failures that can result in the
loss of the safety function.
Figure 64. Category 2 E-stop circuit
Category 3 E-Stop Circuit
A dual-channel hookup switching +24V dc is typically a Category 3
application, because a single failure does not result in a loss of safe-
ty. Loss of the switching action in one channel is detected by the ac-
tuation of the E-stop button, the opening of the second channel, and
the monitoring function of the safety inputs. However, a short circuit
between input channels or Safety Outputs may not be detected. It
should be noted that an accumulation of faults may cause the loss of
the safety function.
The principle of fault exclusion must be incorporated into the design
and installation to either eliminate, or reduce to an acceptable (mini-
mal) level of risk, the possibility of undetected faults or catastrophic
failures that could result in the loss of the safety function.
Figure 65. Category 3 E-stop circuit
Category 4 E-Stop Circuit
The self-monitoring safety inputs can be interfaced to achieve a
Category 4 application. The principle of fault exclusion must be in-
corporated into the design and installation to either eliminate, or re-
duce to an acceptable (minimal) level of risk, the possibility of cata-
strophic failures or faults that could result in the loss of the safety
function.
Figure 66. Category 4 E-stop circuit
Emergency Stop Hookup Options
The device is shown in the armed, or Run, state.
Single-Channel (1 terminal, 2 terminals or PNP device): These
circuits can typically meet ISO 13849-1 Category 2 requirements,
depending on the design and installation of the switch. At a mini-
mum, the switch must be a safety-rated device in order to achieve
Category 2. The 1-terminal and the PNP device can not detect a
short circuit to another source of power. Two-terminal hookup uses
pulse monitoring and can detect a short circuit to another source of
power. Fault Exclusion must be used to achieve higher level of
safety circuit integrity. 24V
SC22-3/-3E Safety Controller Instruction Manual
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