Manhole cover is installed on the top of the tank, also called steel round clamp, fuel truck Manlid with functions of breathing and emergency vent, breathing valve inside the tank in the process of transporting oil pressure of internal and external balance. Emergency exhaust system in the case of a dramatic increase in the tank, even in the condition of the oil tank accidents, prevent overflow device is still within the breathing valve.

Even in the event of an accident in the fuel truck, the anti overflow device of the inner breather valve can still be sealed to prevent the occurrence of an accident.