Special care must be taken when filling and emptying fuel tanks. This is hazardous work that poses explosive, ignitable and toxic hazards for most types of substances carried, including light and heavy petroleum products. Work must only be carried out by persons who have TDT authorisations to operate the UNO. In order to obtain them, it is necessary to obtain training and to take an examination before a commission of the Transport Technical Supervision.Filling can be carried out in several ways, including through the top hatch or through the side drain valves, the tee or the top valve from below. Before filling the tank, the wagon must be carefully rolled to the loading area and blocked with wooden elements. Personal protective equipment is required for the work. The earthing must also be connected and the condition of seals and sealing points checked.

When filling fuel tanks from the top, it is necessary to check the closure of the main valve, then open the top hatch, open the aeration nozzle and start the pump, constantly checking the filling level of the tank and the presence of faults and leaks. The total weight of the load must not be greater than the size of the fixed weight for the wagon. Finally, the top manhole, aeration spigot, cap, handwheel and side drain valves must also be sealed. Check that the taps and valve for the heating system are closed. When filling the tank from the bottom, the same procedure should be followed - the UNO course provides detailed information on the procedure with exercises.

Emptying takes place through the main valve and one of the side discharge valves using a pump or by gravity. Preparatory operations are similar to those for filling the tank. When emptying, connect the discharge line to the side discharge valve, open the valve, the aeration stub or the top hatch in case it is not present, and the main valve. When finished, proceed in a similar way as for the completion of the filling of the tank, remembering to carry out the operations to drain off all the product.