A relay contact-based interface module was installed in between Safety Group's storage vault door enable junction box and Remote Handling's control module for the vault door.

The purpose of this module, which contains a diode bridge and relay, is to isolate the safety system from the control module to prevent back-voltage on the safety system which can damage the PLC's power supply.

In the new configuration, rather than receiving a 24 VDC signal from the safety PLC, this signal activates the relay, whose normally closed contacts supply 24 VDC (from internal) to the safety relay inside the control module. Wiring was modified inside the control module to account for this change.

In investing how to achieve the same functionality as before this change, it was determined that the control module's electrical schematic was not correct and did not reflect the actual wiring. A new schematic was created for this based on the actual wiring, including new changes.

The system was tested by locking out the target hall, and verifying that:
- No failure occurred on the power supply for the safety PLC
- This new relay actuated when the target hall was locked out (i.e. received signal from PLC)
- This new relay correctly supplied 24 VDC to the safety relay within the control module, allowing for the Opto-22 control unit to output control signals to the motors

Note: currently the soft limit switches for the vault door close/open have been bypassed. This is not a safety issue; the door can still be fully opened and closed remotely (but the open override and close override buttons are rendered useless). The bypass will be rectified in the coming weeks and this e-log will be updated accordingly.

Edit (Aug. 13, 2020): the issue regarding the limit switches has been resolved. The entire system is functioning as it was prior to the safety interface installation.