When you choose to install a new manhole cover, your supplier will definitely ask you Clear Opening Size. If you are not professional, you may not know too much.
About Manhole Cover Clear Opening Size. It should be more exactly the same size as Manhole. If you can’t find the same size. Then the Clear Opening Size can be slightly larger than the size of the manhole. But remember, just a little bit.
The Clear Opening Size must not be smaller than the size of the Manhole, as this will reduce the force-bearing area of the Manhole Cover frame, and there is a risk of the manhole cover falling.
You can refer to the figure below to understand what is Clear Opening Size.
1 is the size of manhole cover
2 is the size of manhole cover frame
2 should be same as manhole size, or maybe a little bit lager