Why can't the manhole cover be opened on a hot day?

Corrosion and deformation of manhole cover.

1. The manhole cover is rusty. The manhole cover is exposed for a long time, which is easily corroded by natural factors such as oxygen, moisture and dust, resulting in rust on the surface of the manhole cover. When the manhole cover rusts, the rust layer will narrow the gap between the manhole cover and the wellhead, resulting in the manhole cover being stuck and difficult to open.

2. The manhole cover is deformed. In the process of use, the manhole cover may be deformed by external forces such as vehicle rolling and heavy object extrusion. When the manhole cover is deformed, the gap between the manhole cover and the wellhead will also become smaller, resulting in the manhole cover being stuck and difficult to open.