Range of application

The Ex solenoid and pneumatic interlocks ensure that sliding, hinged and removable guarding devices, such as grids, hoods or doors, cannot be opened until dangerous conditions (e.g. run-on movements) have been terminated. This takes place in co-ordination with the control system of a machine. Fail-safe standstill monitors or delay timers monitor run-on movements or time sequences. These Ex solenoid and pneumatic interlocks are also used for cases in which the opening of a guarding device represents a non-permissible intrusion in a production process.

In combination with the SRM range safety relay module, the AZM and AZP range Ex solenoid and pneumatic interlocks achieve SIL 3 according to EN 62061 and PL e according to EN ISO 13849-1, subject to suitable circuit arrangements.

Design and operating principle

On the Ex solenoid and pneumatic interlocks, the switching element with interlock is not physically connected to the actuator but functionally united or separated on switching.  When the guard device is opened in the uninterlocked condition, the actuator is separated from the base unit. In the process, NC contacts are positively opened and NO contacts closed. The machine control circuit is only activated when the actuator has been inserted into the interlock and is interlocked. The Ex solenoid and pneumatic interlocks operate on the principle of »actuated without power supply«, whereby the actuator is held in the interlock by spring pressure. When power/air is supplied to the solenoid/pneumatic cylinder, the interlock is released. The guarding device can then be opened. The Ex solenoid interlocks with the power-to-lock principle work in the opposite way.

The Ex solenoid interlocks shown in this chapter bear the CE mark according to the Machinery Directive 2006/42/EC and according to ATEX 2014/34/EU. The Ex solenoid interlocks per equipment category 3D bear the CE mark without the number of the notified body and have received a EU declaration of manufacturer conformity.


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