... what is the difference between a process guard locking and a safety guard locking?

DIN EN ISO 14119:2014 describes the function of an interlocking guard with guard locking.

Its purpose is to hold a guard in the closed position so that:

•  the machine cannot be in operation if the protective device is not closed and locked   
•  the guard remains locked until there is no longer any risk of injury                                   

While a process guard locking is open without voltage according to the open-circuit current principle, a safety guard locking works according to the closed-circuit current principle and is therefore closed without voltage, as the actuator is held in place by spring force. On the other hand, an electromagnet is used for a process guard locking. The door, or a similar access, is thereby kept closed by magnetic force. If the magnet is no longer energized, the process guard locking can open immediately.

 

Due to these requirements, it is important to differentiate between a process guard locking and a safety guard locking,

because there are significant differences in the mode of operation.

For example, if the system loses power due to a power failure, the door could be immediately opened while movements inside the system are still running out. For this reason, the run-down time as well as the calculation of the safety distance to the danger point (see page 6/7) must always be taken into account when process guard locking devices are used.

In simplified terms, it can be said that safety guard locking devices are used for systems with a long run-down time and process guard locking devices are used for systems with a short run-down time. Specifi cally, the C standard for packaging machines, DIN EN 415-5:2010-04 in Section 5.2.2.1.7, defi nes the stopping time more precisely. If the system comes to a standstill within one second after opening the guard, a process guard locking can usually be used.