Light hole

The aperture is, of course, adjusting the intensity of light.

The aperture is to allow light to enter and see clearly.

The aperture is circular below the through aperture and has holes of different sizes, which can be adjusted independently according to the observation.

The light intensity can be adjusted by rotating the aperture so that the aperture of different sizes is directly below the aperture.

The through hole is divided into three types according to its use. The size of the through hole is 420X380. Each type of manhole cover has its position to be used.

The through hole is divided into A, B and C according to its use. Each type of manhole cover has its position to be used. The type of through hole is generally determined according to ship design and classification society specifications. The standard size of the manhole cover is 420X380, which accommodates one person in and out, and the larger size is used to carry the wounded out of the accident below.

There is also a kind of manhole cover used in storage tanks, manhole cover is also called atmospheric pressure manhole cover, quick opening manhole, chemical vehicles manhole cover for the flange manhole cover. The manhole cover is mounted on the top of the tank body of a chemical vehicle. It is a passage for people to enter and exit the tank, an observation port for checking the natural conditions of the cargo and the tank.