At a glance

General safety switch knowledge

Escape release

In the event of danger, the escape release device must enable unlocking from the danger area/machine side without the use of aids. The device must be hand operated and act positively on the locking device. Actuation must lead to permanent blocking of the guard locking (see also auxiliary unlatching device).

Emergency unlatching / emergency unlocking

Emergency unlocking is used to unlock a guard locking device in an emergency. Unlocking can be carried out from the access/external side without any tools. During emergency unlocking, the switch engages in the unlocked position and can only be reset to the initial position with a repair-like effort.

Safety Integrity Level (SIL)

Safety Integrity Level is the level that describes the probability that a safety-related system will perform the required safety functions as required under all specified conditions within a specified period of time. For this purpose, the Safety Integrity Level to be achieved (SILr; the “r” stands for “required”) is compared with the “actual” SIL that is achieved.

Auxiliary unlatching

If a guard locking device fails, it can be unlocked from the access/exterior side using an auxiliary unlatching device. Unlocking is done with a tool or a key. The auxiliary unlatching device should be secured against misuse (seal, varnish).

Performance Level (PL)

Discrete level that specifies the ability of safety-related parts of a control system to perform a safety function under foreseeable conditions (definition according to standard DIN EN ISO 13849). Put simply, the performance level is a measure of the reliability of a safety function. A distinction is made between the performance level to be achieved (PLr; the “r” stands for “required”) and the “actual” PL that is actually achieved. There are five performance levels that stand for different residual risks.