The locking pin is a part of the layers of protection on the operation of the DeltaValve. It prevents the inadvertent operation of the valve, which is a good thing. I am aware of a site that had an operator injured when they were attempting to install the locking pin with the bottom head in the open position. I believe they elected to leave the locking pin out when the valve was in the open position. As far as I know, that is the only site that has elected to keep the locking pin out while the unheading device is open. In all cases, the locking pin is installed when the unheading device is closed.
I am also aware of other sites that have installed a hydraulic cylinder to remove and install the locking pin remotely. That is my preference as the locking pin provides positive limitation on the valve being able to move. Removing and installing the locking pin remotely prevents the personnel hazard. I know that both DeltaValve and IMI Z&J have provided remote actuation of the locking pins.