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Why The Cover Is Round?
- Jan 17, 2018 -

No diameter of the dome will be smaller than the circle it is placed on, and the lid will not fall off. Any side of the square cap is shorter than the diagonal of the square ring, but the lid will fall off

This is a figure that has been determined after many attempts. Only the circular covers can not find a diagonal. The distance between each point and the corresponding edge is the same. And take the square point of view, his side length and its diagonal length is different, so when the cover moves only when it is only circular * security. And the cover made of the same material is also circular in area *. If it is placed wellhead, no matter how it is placed, it will be slightly smaller than the diameter of the wellhead, so it will not fall underground and operate downhole Staff is safe.

Before answering this question, let's look at what is under the cover. The hole under the lid is round because the cylindrical shape * can withstand the pressure of the surrounding land. Moreover, the sewer manhole means that there is enough space for one person to pass, while the cross section of a person who climbs down a ladder is substantially round. Therefore, the shape of the round hole naturally becomes a sewer hole. The round covers are just to cover the circular openings.

Square covers sometimes appear on some square openings. This cover than the entrance, surrounded by cross-pieces. Usually this cover is metallic, very heavy. We can imagine two square feet of square holes, 1 to 1.5 inches wide cross-section. To get the manhole cover in, lift one end and then rotate it 30 degrees so that it is not obstructed by the rungs and then cover the manhole at a 45-degree angle to the horizon, shifting the center of gravity enough to allow the manhole cover to fall. Yes, it is possible for the manhole to fall, but the probability is very small. He would not make such a mistake as long as he trained a man in charge of manhole coverings. From an engineering point of view, the shape of the manhole cover depends entirely on the shape of the hole it covers.