Protective door monitoring with tumbler to SIL 2 or PL d with a 3SK2 safety relay
Protective doors are frequently used to fence off danger zones. These are monitored for position and, if necessary, the area from which the hazard emanates is switched off. If the machine continues to present a hazard even after switching off, access can be prevented for this period by a tumbler.
The position of a protective door is monitored via one safety switch. In addition, the door is locked via the safety switch. If the command to unlock the door is issued, the safety relay triggers and opens the enabling circuits, witching off the power contactors in a safety-related manner. The tumbler is unlocked after expiry of a set time. If the door is closed and locked, and the feedback circuit is closed, the Start button can be used to switch on again.
The safety function "Protective door monitoring" and the safety function "Protective door tumbler" are designed for up to SIL 2 or PL d.
Taking account of fault exclusions, use of only one safety switch with or without tumbler is permissible to SIL 2 or PL d. For further information, refer to the letter given below.
Letter concerning the use of safety relays to SIL 2 or PL d 35443942