GTG-series light transmission hole is set on the top of the tank, which is used for lighting and ventilation during tank installation and cleaning, and the upper part of the light transmission hole is connected with the ventilation hole, and is usually closed with an eye circle blind plate. When washing the oil tank, open the blind plate of the eye circle, connect the ventilation hole, and the tank can be mechanically ventilated. GTG-series light transmission hole is installed on the top of the oil tank, for the lighting in the tank, A type is installed in the flat cone item tank, 8 type is installed in the arch oil tank, and the C type is installed in the heavy oil tank, this product leaves the factory without a reinforcement plate.