What is the difference between a light hole and a manhole?

The light openings are mainly used for lighting on the top of the tank; they are not accessible and do not need to be as large as manholes. Theoretically, human hole standards should also be applicable. Light-transmitting holes are also standard attachments for storage tanks and can be selected.

I don’t think it’s necessary; the light-opening is intended solely for lighting the top of the tank. By adopting the standard for manholes, only the area through which light can pass can be increased, and this has little to do with anything else.

The light ports and manholes differ in size in terms of flange, blind plate, and diameter.

Using manholes as light-transmitting openings is completely pointless; it only increases costs, as standard manholes are several times more expensive than those designed for light transmission.

After reading the reply, I still don’t understand. Are the production standards for the light-transmitting holes lower? Should the dimensions just be followed as specified in the catalog? Is that how it should be understood?

No, light holes and manholes are two different things; they serve different purposes, are located in different places, and of course, their installation methods also differ. Generally, the light-transmitting holes are used for allowing light to pass through; they are opened during maintenance to increase the amount of light inside the tank, and are usually installed at the top of the storage tank ； The function of the manhole is mainly to allow personnel to enter and exit the storage tank, and it is generally located at the bottom of the tank. From a pressure-bearing perspective, light-transmitting holes are not subject to pressure, while manholes generally have to withstand the hydrostatic pressure generated by the height of the fluid inside the tank; hence they are under greater pressure, and the welding requirements for them are naturally different from those for light-transmitting holes

Manholes: DN500, DN600, DN750. Manholes are provided for operators to enter and exit the oil tank during cleaning and maintenance tasks. Lighting hole: Also known as a ventilation hole, it is provided for lighting and ventilation during the cleaning or maintenance of oil tanks. It is usually installed on the tank top above the inlet and outlet pipes of the oil tank, with a diameter of generally DN500; its outer edge is located 800~1000 mm away from the tank wall, and the number of such units is the same as that of the manholes.