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The ductile iron manhole cover is mainly made of ductile iron, or often called nodular iron. The quality depends on the nodularity. Anti-rust asphalt paint is commonly used in the casting process. In other words, the surface of ductile iron manhole covers are generally sprayed with asphalt for anti-rust treatment. Features of ductile iron manhole cover: 1. High strength The tensile strength of ductile iron is greater than 420Mpa; the yield strength is greater than 300MPa. Same as low carbon steel, it is more than 3 times that of gray iron. 2. Good toughness. The impact value is similar to that of carbon steel and 10 times that of gray iron. 3. Good plasticity. The elongation rate is greater than 7%, which is similar to high-carbon steel and gray iron materials. 4. Corrosion resistant. In the 90-day spray corrosion test performance of ductile iron, the corrosion was only 0.25 times that of pipelines and 0.1 times that of gray cast iron pipelines. The service life is 2 times longer than gray cast iron pipes and 5 times longer than ordinary steel pipes. In most municipal applications, such as water, salt water, steam, etc., the corrosion and oxidation resistance of cast iron exceeds that of steel. Due to the microstructure of spherical graphite cast iron, nodular graphite cast iron is better than steel in reducing vibration capabilities. Advantages of ductile iron manhole cover: 1. Low cost Low cost is an important reason why cast iron is more acceptable than steel, which makes ductile iron more popular. The casting efficiency is higher, and the processing cost of ductile iron is lower. 2. Lightweight There is another advantage of ductile iron manhole covers. Ductile iron has high strength and toughness, which makes ductile iron manhole covers 30% lighter than similar manhole covers made of gray cast iron.

There are many types of manhole covers, single-layer, double-layer, cast iron manhole covers, ductile iron manhole covers, composite manhole covers, cement concrete manhole covers, etc. Among them, ductile iron manhole covers are the most widely used. According to the En124 standard, manhole covers are divided into six grades according to the load-bearing capacity : Group 1 （A15）— areas where only pedestrians have access. Covers and gratings capable of withstanding a 15kN test load. Group 2（B125）—car parks and pedestrian areas where only occasional vehicular access is likely (incl. driveways). Covers and gratings capable of withstanding a 125kN test load. Group 3 （C250）— car parks, forecourts, industrial sites and areas with slow moving traffic. Also in highway locations up to 500mm from the kerb and up to 200mm into the verge, excluding motorways. Covers and gratings capable of withstanding a 250kN test load. Group 4 （D400）— areas where cars and lorries have access, including carriageways, hard shoulders and pedestrian areas. Covers and gratings capable of withstanding a 400kN test load. Group 5（E600） — areas where high wheel loads are imposed, such as loading areas, docks or aircraft pavements. Covers and gratings capable of withstanding a 600kN test load. Group 6（F900） — areas where particularly high wheel loads are imposed such as aircraft pavements. Covers and gratings capable of withstanding a 900kN test load.  

Resin manhole covers are used on the roads, which have the characteristics of insulation, no noise, no recycling value and natural anti-theft. They are irreplaceable for cast iron manhole covers. The resin manhole cover is made by a unique molding process, which makes the city look like a new one. The service life is basically 20-50 years. The resin composite manhole cover molded by high temperature has light weight, high strength, excellent fatigue resistance, and damage safety. , Simple molding, low rolling noise, good chemical corrosion resistance, good acid and alkali resistance and beautiful appearance, etc., and the pollutants in the wastewater are further reduced.   Now on the market, the manhole covers produced by various composite manhole cover manufacturers use different materials, but several characteristics are similar: 1. Strong anti-theft performance: composite manhole cover manufacturers generally use unsaturated resin, glass fiber and other materials to compound them through a special production process. After high temperature molding, the product has no recycling value. 2. Service life: Through the use of high-performance resin, glass fiber and special production process formula, the penetration of the composite manhole cover in the glass fiber is ensured, and the bonding force between the two is greatly enhanced, so that the material will not be affected by the cyclic load. Internal damage occurs, thereby ensuring the service life of the product and the same advantages of other resin composite manhole covers, effectively eliminating the disadvantages of poor adhesion. 3. High temperature/low temperature resistance, good insulation performance, strong corrosion resistance: the product is corrosion resistant, non-toxic and harmless. No metal additives. It can be used in complex, changeable, harsh and demanding places. It has obvious acid and alkali resistance, corrosion resistance, anti-aging and many other indicators that have reached product quality specifications. 4. 4. Beautiful and practical, high-grade: According to the needs of high-end customers, a personalized design with complex LOGO and multiple colors on the same manhole cover can be made to make the pattern delicate, bright and distinct. And according to customer needs, it can be made into a variety of imitation stone appearances and colors that are the same as various stone pavements. 5. Strong load-bearing capacity: The bottom adopts a special design structure, and the continuous reinforcing fiber yarns used are made from the material to ensure that the fiber yarns and glass fiber cloth are integrated, so that the product has a certain load-bearing capacity. 6. Environmental protection, non-slip, low noise: The manhole cover will not slip after the car is rolled, and there will be no back-ear noise and pollution. （ Electronical manhole covers）