6 muting time limit (backdoor timer), 7 mute on power-up, 9 multiple presence-sensing safety devices – Banner SC22-3E Safety Controller with Ethernet User Manual
Page 120
Lamp monitoring must be selected if the application requires compliance with UL 61496.
10.11.6 Muting Time Limit (Backdoor Timer)
The muting time limit (backdoor timer) allows the user to select a maximum period of time that muting is allowed to occur. This feature
hinders the intentional defeat of the muting devices to initiate an inappropriate mute. It is also useful for detecting a common mode failure
that would affect all mute devices in the application.
The timer begins when the second muting device makes the simultaneity requirement (within 3 seconds of the first device), and will allow
a mute to continue for the predetermined time. After the timer expires, the mute ends – no matter what the signals from the mute devices
indicate. If the input device being muted is in an OFF state, the mapped OSSD outputs will turn OFF and must be manually reset (if the
input device is configured for manual reset).
WARNING: . . . Muting Time Limit
An infinite time for the backdoor timer (i.e., disabling) should be selected only if the possibility of an inappropriate
or unintended mute cycle is minimized, as determined and allowed by the machine’s risk assessment. It is the user’s
responsibility to ensure that this does not create a hazardous situation.
10.11.7 Mute on Power-Up
If selected (see section
on page 37), the Mute on Power-Up function will initiate a mute when:
• Power is applied,
• The Mute Enable input is closed (if configured),
• The safety device inputs are active (closed), and
• Either M1-M2 or M3-M4 (but not all four) are closed.
If Normal or Automatic Power Up mode is configured and all other mute conditions are satisfied, a mute event will start immediately.
If Manual Power Up mode is configured and all other mute conditions are satisfied, the first valid System Reset will result in a mute
event.
WARNING: . . . Mute on Power-Up
The Mute on Power-Up function should be used
only in applications where:
• Muting the System (M1 and M2 closed) when power is applied is required, and
• Using it does not, in any situation, expose personnel to any hazard.
10.11.8 Corner Mirrors, Optical Safety Systems, and Muting
Mirrors are typically used with safety light screens and single-/multiple-beam safety systems to guard multiple sides of a hazardous area.
If the safety light screen is muted, the safeguarding function is suspended on all sides. It must not be possible for an individual to enter
the guarded area without being detected and a stop command issued to the machine control. This supplemental safeguarding is normally
provided by an additional device(s) that remains active while the Primary Safeguard is muted. Therefore, mirrors are typically not allowed
for muting applications.
10.11.9 Multiple Presence-Sensing Safety Devices
Muting multiple presence-sensing safety devices (PSSDs) or a PSSD with multiple sensing fields is not recommended unless it is not
possible for an individual to enter the guarded area without being detected and a stop command issued to the machine control. As with
the use of corner mirrors (see section
10.11.8 Corner Mirrors, Optical Safety Systems, and Muting
on page 120), if multiple sensing fields
are muted, the possibility exists that personnel could move through a muted area or access point to enter the safeguarded area without
being detected.
SC22-3/-3E Safety Controller Instruction Manual
120
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