Banner MMD-TA-11B Muting Modules - Manual (Page 30)

28
P/N 116390 rev. C
Banner Engineering Corp. • Minneapolis, U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
MMD-TA-11B / MMD-TA-12B Muting Module
Instruction Manual
System Installation
Category 3
A dual-channel hookup switching +24V dc is typically a category
3 application, because a single failure does not result in a loss
of safety. Loss of the switching action in one channel is detected
by the actuation of opening and closing the guard, allowing
the monitoring function of the MSSI or SSI inputs to detect the
discrepancy between the channels. 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 (minimal) level of risk, the possibility of undetected
faults or catastrophic failures that could result in the loss of the
safety function.
Category 4
The self-monitoring MSSI or SSI inputs can be interfaced to
achieve a category 4 application. 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 catastrophic failures/faults that could result in the
loss of the safety function.
Open
(a)
(b)
(c)
(d)
MMD-TA-..B
A1 A2
X6
X5
X8
X7
S12
S11
S22
S21
MSSI or SSI
+24V dc 0V dc
NOTE: Two independently mounted positive-opening switches
per guard.
Figure 3-21. SSI Category 4 interfacing: positive-opening
interlocking switch(es)
(a)
(b)
(c)
MMD-TA-..B
A1
0V dc +24V dc
A2
X6
X5
X8
S12
S11
S22
(d) X7 S21
MSSI or SSI
Open Open Open
WARNING . . .
Series Connection
of Safety Switches
When monitoring multiple guards
with a series connection of multiple
safety interlock switches, a single
failure may be masked or not
detected at all.
When such a configuration
is used, procedures must be
performed regularly to verify
proper operation of each switch.
See “Monitoring Series-Connected
Safety Switches”
(page 26) for more information.
Failure to do so could result in
serious injury or death.
NOTE: The interface is still considered a category 3 application if the hookup of each
channel is a closed loop (S11 to S12 and S21 to S22) due to the possibility of a
“series failure.” See warning at right.
Figure 3-20. MSSI or SSI Category 3 interfacing: Positive-opening Interlocking switch(es)