The first sewer hatches appeared more than one and a half hundred years ago. In those days, public utilities began to actively develop in large cities. Sewer systems were created from interconnected wells. Hatches with covers were used to close the places where the wells exited to the surface. They had at first a very different shape, but gradually the round shape supplanted other types of hatches. Why did this happen?
Instructions
Step 1
In the assortment of foundries, cast iron sewer manholes are far from the last. At the end of the 19th century, there were a lot of such enterprises, and each of them produced hatches for its own city or even district. There were no uniform standards, there was a wide variety of shapes and sizes of foundry products. By the hatch covers produced in those days, one can trace the geography and the specifics of the urban economy.
Step 2
With the appearance of cars on the streets of cities, new requirements were imposed on the hatches, because heavy trucks could exert several tons of pressure on the covers of sewer wells. Hatches began to be designed in accordance with the class of roads, their purpose and the intensity of traffic flows. Standards began to be developed concerning the dimensions of the hatches, their shape and the permissible weight of the covers.
Step 3
Gradually, the sewer hatch took on the rounded shape familiar today. Those covers that were installed on the roadway began to be supplied with a tail section protruding into the well, which served as a kind of stabilizer. Such a device prevented the hatch cover from sliding to the side when the car wheels hit it.
Step 4
Why is the round shape chosen for most of the hatches? There are several reasons for this. Firstly, products of this shape are very simple to manufacture, it requires less material than any other of the same size. Secondly, the round cast-iron lid is easier to transport or even just roll from place to place.
Step 5
Another reason concerns the safety in the operation of wells. The fact is that under no circumstances can the round hatch cover fall into the well, which is explained by the peculiarities of this geometric shape. But the square lid may well pass through the neck of the well if its edge is placed on the diagonal of the square, which can be dangerous to the life and health of workers when carrying out repair and maintenance work inside the engineering structure.
Step 6
However, there are still square or even irregular manhole covers today. As a rule, they correspond in shape to the wells that are designed to close. When choosing a shape for a hatch, manufacturers are often guided by the purpose of the wells. Such engineering structures are used not only in the construction of sewerage systems, but also in the creation of water supply systems, heat and gas networks.
