SafetyLab

Function package „Muting“

The muting version of the receiver or transceiver makes it possible to connect up to four muting sensors and optionally a number of monitored muting indication lamps.The muting indicator shows to staff members by being continuously lit that muting operation has been correctly initiated and the protective field safety function is bypassed.

A muting indicator must be connected in all muting modes as long as the monitoring function has not been deselected with SafetyLab.

Muting operation is initiated by at least two independent muting sensors.

Criteria for initiating muting operation might include:

• Order of sensor activation
  
  
• Time expectation of sensor activation
  
  

The function package "Muting" offers the following options:

• Bypassing a safety device for a limited time (several types of muting)
  
  
• Deselectable muting indicator monitoring
  
  
• Additional control signals for muting
  
  
• Filtering of muting sensor signals
  
  
• Releasing the muting station with muting restart
  
  
• Optionally controllable muting time limit
  
  
• Defining a beam zone with reduced resolution,
  
  

Application example

Problem:
A pallet transfer station is secured with a muting transceiver with integrated LED muting indicator. Since only limited space is available, muting will be activated with a reflex light barrier that is aligned diagonally over the conveyor belt and the conveyor belt control signal from a PLC. After the pallet has been placed on the conveyor belt,the PLC starts the drive. The pallet reaches the reflex light barrier and starts muting within a time window of 1 s < t < 2 s. The pallet moves through the safety equipment in normal mode within a few seconds. The muting time limit should therefore be reduced to a value of 20 seconds. If the conveyor belt comes to a stop, the muting timer stops so as not to generate an error message (which would require an operator to release it for continue production). Since the good on the pallet is covered with plastic, the light barrier may be disturbed by brief reflections during the muting. Most of these error signals will be filtered out. A number of pallet transfer stations of this type are arranged next to each other. Because of this, the OSSD status will be displayed locally to let the operator know what protective equipment might need to be restarted so that the station can be released again with the local start button. A pilot light turns on as soon as the OSSDs are turned off. The safety distance between the protective equipment and the danger point is sufficiently large so that the protective field can be set to be as insensitive as possible to interference.

Solution:
2-sensor parallel muting (L1, M5) is selected. This makes it possible to connect the muting light barrier conveniently to L1 locally while the PLC control signal to M5 is connected through the machine interface cable. Thus there is no need for a separate cable from the cabinet to the local interface. The control signals for the muting timer is also sent to M1 through the machine interface. The non-safe PLC must ensure that this signal is log. 0 when muting is activated and that it only switches to log. 1 when the conveyor belt stops during muting. If this procedure is not followed, error E53 is generated. To switch this signal only during muting, COMPACTplus reports "Muting activated" to the PLC via M3. The OSSD state is generated inversely and displayed on L2. For safety reasons, signal filtering for L1 is increased to a 100 ms on delay and 500 ms off delay. The simultaneousness expectation of parallel muting is increased to 0.5 s < t < 1.5 s. A muting prolongation of 1 second ensures that the pallet will have left the safety equipment before the end of muting.