Parallel conditions of Safety Relay Input

[SiiD 0]

Hello everyone,

I wonder is it possible to parallel contact for safety input.

I not sure if safety standard allow to do so.

Have anyone did so? Please suggest.

Thanks a lot.

 

Edited 25 Mar 2019 by SiiD

[mikeexplorer 12]

As a general rule, all safety contacts must be in series. So all conditions must be met for control power to be activated.

Attached is a schematic from a machine showing the daisy chain of Emergency stops along the machine, notice all are in series, the extra connections coming off each one goes back to a PLC as input so you can identify what part of the machine has its E-stop triggered. The condition is displayed on a HMI panel. The PLC only reads the condition.

The control power is a relay that must be energized to allow operation.

Nowadays, this is done with a safety relay that has forced contacts. Example of this is Pilz PNOZ type relays. This machine is older and only uses a standard mechanical relay.

Mike

 

[SiiD 0]

Thank you for your answer.

I got alternative solution apart from safety relay.