The importance of manhole covers in municipal engineering is well known, but the types of manhole covers used in different situations are different. What are the advantages and disadvantages of various manhole covers?
According to the shape: the manhole cover is generally divided into circular and square. On urban roads, it is generally round. Because the round manhole cover is not easy to tilt, it can better protect the safety of pedestrians and vehicles. When using a circle, the main consideration of the round manhole cover is The diameter is the same for each diameter through its center, so that if the manhole cover is rolled up by the vehicle, the diameter will be slightly wider than the wellhead below, and the manhole cover will not fall into the wellhead.
If a square is used, the diagonal of the square is significantly longer than the length of each side. When such a manhole cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, causing hidden safety hazards. If the wellhead is round or significantly smaller than the manhole cover, the square manhole cover will not fall into the well. This is a matter of maximum material utilization and economy. The use of a wellhead depends on the size of the wellhead. If it is necessary to install a square manhole cover with a much larger area than the wellhead, the use of materials and practical value will not directly and more effectively use the round shape.
Manhole cover according to the material: currently used manhole cover has the following types: cast iron manhole cover, cement manhole cover, silicon plastic manhole cover, polymer molding manhole cover, etc.
Cast iron manhole cover
Cast iron manhole covers are ductile iron and grey iron.
(1) Gray cast iron manhole cover:
It has a certain carrying capacity and is cheap, but it is brittle, easy to rust, and easy to be stolen. It is mainly used in general load-bearing areas and residential areas.
(2) Ductile iron manhole cover:
Compared with the gray cast iron manhole cover, the bearing capacity is improved, the toughness of the material is relatively difficult to rust, and it is mainly used in main lanes and roads with large bearing capacity. However, prices have risen sharply and, similarly, they are easily stolen because of their recycling value. In order to solve the problem of anti-theft, a number of locked cast iron manhole covers have been developed. Although the security problem has been improved to a certain extent, some people have broken the manhole covers, stole the manhole covers, or cannot use professional lock keys to prevent professional theft. And often the lock is affected because the lock is rusted. The further increase in cost has brought economic and user difficulties to the user.
2. Cement manhole cover
The cement manhole cover is filled with high-grade cement in the steel frame or mixed with the steel frame or steel fiber in the cement. It has strong rigidity, brittleness, resistance to acid and alkali corrosion, easy ageing, easy fracture, and poor bearing capacity, leading to another This form of manhole cover is missing, and the cement manhole cover is gradually withdrawing from the market in many cities.
3. Silicone manhole cover
Silicone manhole cover is a composite manhole cover made of fly ash, waste plastic, waste rubber and resin as adhesive .. It is brittle in winter, insufficient in bearing capacity, soft in summer, and difficult to open under high temperature creep. Mainly used in residential areas and auxiliary roads, not suitable for main lanes .. easy to age and short life.
4. Polymer molded manhole cover
The new polymer composite molding manhole cover is suitable for automated production of machinery. Its load, safety, economy, corrosion resistance, decoration and other aspects have been well combined, and its bearing capacity has reached more than 50 tons of the national authority. Therefore, it is currently the only composite manhole cover that can completely replace the nodular cast iron manhole cover, which not only saves the material of the manhole cover, but also guarantees the safety of the wellhead.