The Personal Safe is a chest-like item added by IndustrialCraft2 with a storage capacity of 54. The safe will bind to the first person to access (open) it. After the safe is bound, only the owner (and server operators) can access it or use a Wrench to remove it. If any other players attempt to open or break the safe, it will inform the player to whom the safe belongs, unless you happen to be an op of the server. If you changed your nickname (starting game in offline mode changes your nickname to "Player") you will lose access to your safe.
In order to use a Wrench to remove a safe it has to be empty. You will always get the safe back through wrenching.
The safe can be destroyed if a reactor overheats and spawns lava in the same block space as the safe.