Manhole covers can be classified by shape into: circular, square and rectangular, among which the circular ones are the most widely used.

       Manhole covers can be classified by shape into: circular, square, and rectangular, among which the circular type is the most widely used. By load-bearing capacity, they can be divided into: ordinary, heavy-duty, super heavy-duty, and light-duty. By material, they can be classified as: ductile iron, reinforced fiberglass, steel fiber, resin-molded composite, recycled resin composite, silicon plastic, etc. By user application, they can be categorized as: municipal, water supply, telecommunications, power, fire protection, etc. According to national standards, they can be classified as: single-layer, double-layer, cast iron, ductile iron, composite, cement, magnesite, etc.

       Selection of manhole cover materials:

       1. Cast iron manhole covers can generally be divided into ductile iron and gray cast iron manhole covers. After testing, it is found that manhole covers made of ductile iron have stronger compressive strength than those made of gray cast iron under the same weight. Due to the low price and quality guarantee of cast iron manhole covers, more and more enterprises and governments are willing to choose them.

        2. Ductile iron manhole covers are made of ductile iron. The advantages of this type of manhole cover are good toughness, strong corrosion resistance, good plasticity, and high strength. Another important reason for choosing ductile iron as the material for manhole covers is that it is cheaper than cast steel. The low cost combined with a high casting rate makes this material more popular.

        3. Although gray cast iron manhole covers do not have as strong compressive strength as ductile iron manhole covers, they are more widely used compared to the latter. This is because the plasticity and toughness of gray cast iron manhole covers are highly commendable, and their overall performance is also relatively strong.