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Rockwell Automation Publication 450L-UM001F-EN-P - March 2022
Chapter 4 Safety Function
Muting Sensors
Mechanical muting sensors must have an opening contact. For proper
operation, the muting sensors are on (normally closed) if the safety light
curtain is not muted.
The safety relay, the 450L-E or 450L PAC safety light curtain, and the muting
sensors must have the same reference (24V Com) for proper operation.
Photoelectric muting sensors do not need to be certified according to safety
type 2 or 4 of IEC 61496-1/-2. The detection zone of the muting sensors must be
within 30° of the horizontal and are mounted at a height suitable to detect a
person's leg (see IEC 62046).
Various positions and sizes of materials on the pallet can make it difficult to
guarantee an uninterrupted muting signal over the entire passage through the
guarded area. For this reason, an off-delay time t(msdel) for the muting sensor
inputs and the light curtain is set to 50 ms.
Mute Dependent Override Function (MDO)
Normal activation of the manual start button is only permitted if no muting
sensors are activated and the light curtain is not interrupted.
An error in the muting sequence does not allow a muting condition. If the
safety light curtain is interrupted, the OSSD safety outputs of the 450L-E safety
light curtain switch off. This error typically leads to a cessation of movement.
In such a case, it can be difficult to move the material out of the protected area.
If this situation is anticipated (an error in the muting sequence or timing), the
Reset button provides an MDO (depending on DIP switch settings). The OSSD
safety outputs can be reactivated temporarily by activating the Reset button
(manual start). The maximum allowable duration t
mdo
for this MDO is
provided in
, and
the individual muting types.
The MDO is possible at the same pin when automatic start is configured. For
this case, the connected safety relay or safety logic performs the manual reset.
A push button or a spring loaded keyswitch activates the MDO. The push
button/keyswitch is mounted at a location from which the dangerous area can
be seen.
The MDO is automatically ended after the mute dependent override time
(t
mdo
) has elapsed, or when the safety light curtain is no longer interrupted,
whichever occurs first.
IMPORTANT
Detailed information about muting sensors (for example, positioning) is
given in the standard IEC 62046.
IMPORTANT
The muting sensors detect the material on a pallet and not the pallet
itself.
IMPORTANT
Make sure that the MDO can be installed based on the risk assessment
of the application. Some applications can require a spring loaded
keyswitch for the reset.
IMPORTANT
In muting applications, the reset of the muting function block must be a
manual reset. Either the light curtain and/or the safety relay that is
connected to the light curtain performs the manual reset.
