Machine Safety Switch – SI-LM40 Series Limit Switch Style
4 P/N 49372 rev. D Banner Engineering Corp. • Minneapolis, MN U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
Figure 3. Connect two redundant safety switches per interlock guard to an appropriate
2-channel input safety module.
Safety
Switch
#1
Safety
Switch
#2
Input
Channel
#1
Input
Channel
#2
2-channel Safety Module
(2-channel E-stop Module
2-channel Gate Monitor Module, etc.)
Single gate
or guard
11/15 12/16 11/15 12/16
NOTE: Refer to the installation
instructions provided with the
safety module for information
regarding the interface of the
safety module to the machine
stop control elements.
Electrical Installation
Access to the Wiring Chamber
The wiring chamber is accessed via a cover plate. The metal switch body uses two
screws to hold the cover plate on. A conduit adapter is supplied to convert the
M20 x 1.5 thread to ½"-14 NPT. An accessory cable gland which fits the M20 x 1.5
thread is available (see page 7).
Connection to a Machine
Two types of contacts are offered. The NC contact is the safety contact, which is
closed (i.e., it conducts) when the actuator is engaged. The NO contact is considered a
monitoring contact, which should not be used for safety switching.
As illustrated in Figure 3, a normally closed safety contact (i.e., a safety contact that is
closed when the actuator is engaged) from each of two safety switches per interlock
guard must connect to a 2-channel safety module or safety interface in order to achieve
a control reliable interface to the master stop control elements of a machine. Examples of
appropriate safety modules include 2-channel emergency stop (E-stop) safety modules
and gate monitor safety modules.
Two functions of the safety module or safety interface are:
1. to provide a means of monitoring the contacts of both safety switches for contact
failure, and to prevent the machine from restarting if either switch fails; and
2. to provide a reset routine after closing the guard and returning the safety switch
contacts to their closed position. This prevents the controlled machinery from restarting
by simply reinserting the safety switch actuators. This necessary reset function is
required by ANSI B11 and NFPA 79 machine safety standards.
Use only a positively driven, normally closed safety contact from each switch for
connection to the safety module. The normally open contact may be used for control
functions that are not safety-related. A typical use is to communicate with a process
controller. Refer to the installation instructions provided with the safety modules for more
information regarding the interface of the safety module to the machine stop control
elements.
CAUTION . . .
Electrical Installation
Two safety switches must be
used for each interlock guard to achieve
control reliability or Safety Category 4 (per
ISO 13849-1, EN 954-1) of a machine stop
circuit. Use of only one safety switch per
interlock guard is not recommended.
In addition, normally-closed safety contacts
from each of the two safety switches should
be connected to the two separate inputs of a
2-channel safety module or safety interface,
as illustrated in Figure 6. This is required to
provide monitoring for safety switch contact
failure, and to provide the necessary reset
routine, as required by IEC 60204-1 and
NFPA 79 machine safety standards.
WARNING . . .
Series
Connection of Safety
Interlock Switches
Monitoring multiple guards with a series
connection of multiple safety interlock
switches is not a Safety Category 4
Application (per ISO 13849-1, EN 954-1).
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.