Cut Sheet

guard is cycled (opening and then closing both of the channels), the failure appears to be corrected (input
requirements satisfied) and the module/controller allows a reset. This system is no longer redundant and, if the
second switch fails, may result in an unsafe condition (the accumulation of faults resulting in loss of the safety
function).
• Non-detection of a failure—If a functional guard is opened, both channels open and the module/controller
initiates a protective (safety) stop. If a guard with a faulty safety switch is then opened and closed before the good
guard is re-closed, the faulty switch is not detected. The system is no longer redundant and may result in a loss of
safety if the redundant switch fails to open when needed.
The system in either scenario does not inherently comply with the safety standard requirements of detecting a single fault
and preventing the next cycle (not a Category 4 application per ISO 13849-1). In multiple-guard systems using series-
connected safety switches, it is important to periodically check the functional integrity of each interlocked guard
individually. Open and close each guard separately while verifying that the machine properly responds. Operators,
maintenance personnel, and others associated with the operation of the machine must be trained to recognize
failures and be instructed to correct them immediately.
WARNING: Series Connection of Safety Switches
Monitoring multiple guards with a series connection of safety interlock switches may result in a failure
being masked or not detected at all. When such a configuration is used, periodic checks must be
performed regularly to verify proper operation. All failures must be immediately corrected (for example,
immediately replacing a failed switch), or the loss of the safety stop signal or an inappropriate reset
may lead to serious injury or death.
Maintenance
Checkout
At switch installation or replacement and at machine set up, a Designated Person
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must test each switch for proper
machine shutdown response and check the switch(es) and installation for proper operation, physical damage, mounting
(looseness), and excessive environmental contamination. This must also take place on a periodic schedule determined by
the user, based on the severity of the operating environment and the frequency of switch actuations. Adjust, repair, or
replace components as needed. If inspection reveals contamination on the switch, thoroughly clean the switch and
eliminate the cause of the contamination. Replace the switch and/or appropriate components when any parts or
assemblies are damaged, broken, deformed, or badly worn; or if the electrical/mechanical specifications (for the
environment and operating conditions) have been exceeded. Always test the control system for proper functioning
under machine control conditions after performing maintenance, replacing the switch, or replacing any component of the
switch.
Additional items that should be included in the checkout and/or regularly scheduled maintenance of a safety limit switch,
actuating system, and actuator (cam) are:
• Verify proper positioning of switch, actuating system (for example, roller lever), and cam or dog
• Verify correct switching function (actuator system has free movement and within switching distance specifications)
• Correct any misalignment or overrun between the actuator and the actuator system
Repairs
Do not attempt any repairs to the safety interlocking switch. It contains no field-replaceable components.
Return it to Banner Engineering for warranty repair or replacement.
Contact Banner Factory Application Engineering. They will attempt to troubleshoot the system from your description of the
problem. If they conclude that a component is defective, they will issue a return merchandise authorization (RMA) number
for your paperwork, and give you the proper shipping address.
Important: Pack the safety switches carefully. Damage that occurs in return shipping is not
covered by warranty.
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A Designated Person is identified in writing by the employer as being appropriately trained to perform a specified checkout procedure.
Safety Limit Switches
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