Definition - What does Manhole Cover mean?
A manhole cover is a removable lid that covers the manhole and prevents people and things from falling into it. A manhole cover can be of different shapes like rectangular, square and circle. The most popular choice however is the circular manhole so commonly seen everywhere. Manholes are usually circular and it logically follows to have a circular manhole cover. Circular manhole covers are safe because they will not fall into the manhole where workers may be present.
This may not be the case with square and rectangular covers that can fall in if placed diagonally while it is being aligned. Circular manhole covers are also easy to roll and put into place.
Trenchlesspedia explains Manhole Cover
A manhole cover makes it easy for workers to remove then and enter the manhole to carry out trenchless rehabilitation by utilizing methods such as cured-in-place pipe (CIPP), thermoformed pipe and mechanical spot repair. A manhole can also be used to carry out trenchless inspection in order to find out problematic areas that can then be isolated and repaired. A manhole cover is made with different materials such as cast iron, ductile iron, concrete and in some cases, with glass reinforced plastic (GRP).
Cast iron manhole covers are preferred because they are strong, cheap and easy to cast. A heavy manhole cover is essential to ensure that the cover does not get dislodged by pressure from gasses released in the drains and also from sucking pressure of fast moving vehicles. Unpainted cast iron inherently possesses rust resisting properties that make it an excellent choice to ensure best performance and long service life. Though other materials for manhole covers are available, the strength of cast iron cannot be overstated when it comes to resisting earth and pavement pressures.