A little about refueling.
 

And this is the way we refuel the ships.
We use a no drip coupling, and Bob.
Bob is not a person but a bunker installation.
An optic sensor is placed inside the fuel tank,
and connected to the fuel pump.
As long as the optic sensor can "send and receive",
the pump keeps on pumping.
When the fuel "hits" the sensor it will disconnect the power to the pump,
and the pump stops.
But you still need to monitor the process!!!
So on the photo you se my colleague Theo "guarding" the coupling,
and me (the webmaster) guarding the emergency stop.