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              What are the standards for overflow manhole covers?

              What are the standards for overflow manhole covers?

              2019-10-28 14:45:30 浏览次数: Text: [Big] [Medium] [Small] 2019-10-28 14:45:30 Views:

              What are the standards for overflow manhole covers?

              There are many national standards for manhole covers in China, such as single-layer, double-layer, cast iron, ductile iron, composite, cement, magnesite, and so on.

              According to the very new national standard GB / T 23858-2009,

              Manhole cover load capacity can be divided into the following types:

              One point is that the manhole cover loading capacity and the ability of the manhole cover to pass vehicles are not a concept.

              The manhole cover load capacity refers to the pressure test performed by a pressure testing machine in a unit area, which is usually 40 tons heavy. If it is a passing vehicle, the calculation formula for a 5-axle heavy-duty truck is: 5-axis x 40 tons = 200 tons. With a gross vehicle weight of 200T, the heavy manhole cover can guarantee passage.

              And some manufacturers have said that the technical parameters of 80-ton vehicles, if divided by 5 axles, then its manhole cover load: 80t / 5 = 16t, which means that the manhole cover load is 16 tons.

              According to Item 4 of GB / T23858-2009 "Inspecting Manhole Covers", manhole covers are divided into six levels according to their bearing capacity:

              Group: (Type A15 is selected very low): Green belts, sidewalks and other areas where motor vehicles are prohibited from entering.

              The second group: (B125 type is very low): sidewalk, non-motorized lane, car parking lot and underground parking lot.

              The third group: (C250 type is very low): residential quarters, back streets and alleys, areas with only light motor vehicles or small cars, within 0.5m of curbs on both sides of the road.

              The fourth group: (D400 type is very low): urban trunk roads, highways, high-grade highways, highways and other areas.

              Group 5: (E600 type is selected very low): Cargo terminals, terminals, airports and other areas.

              Group 6: (F900 type is selected very low): Airport runways and other areas.

              Japanese Standard

              Engineering level

              In 1958, Japan imposed mandatory manhole cover standards on manhole cover thickness, material, load bearing and other key indicators. Current industry standards require that manhole covers be cast from high-strength spheroidal graphite cast iron with a thickness of more than 17 cm and a weight of 40 kg.

              The director of the Japan Surface Manhole Industry Association Bureau Moriya said that all sewer manhole covers in Japan are subject to quality inspection by industry organizations such as the Japan Sewer Association. After getting permission, you can leave the factory. After that, there are regular quality inspections every year to ensure the quality of manhole covers through such a supervision mechanism.

              Fit standard

              In China, most manhole covers do not fit tightly to the road surface, and tires can collide with manhole covers when the vehicle is pressed. As a result, manhole covers have become one of the urban noise sources. In the 1970s, many people in Japan suffered from the noise of manhole covers and asked the local governments to solve the "noisy manhole covers". The Japanese government immediately modified the standard for sewer manhole covers, changing the cylindrical manhole cover to the upper and lower conical manhole cover, and required that the manhole cover be cast to the nearest millimeter. In this way, the manhole cover and the road surface can be closely fitted together, which not only eliminates noise, but also increases the difficulty of stealing the manhole cover.

              safe question

              In 2010, a sudden heavy rain fell in Kochi Prefecture, Japan, causing some sewer covers to fall off or break, causing many pedestrians to fall into the sewer. The Ministry of Homeland Security of Japan immediately convened experts and local governments to set up a "Sewer Manhole Emergency Safety Countermeasure Committee" to conduct field investigations of the sewer site where problems occurred. The investigation found 8 types of manhole cover safety issues that needed to be resolved, and formulated the corresponding "emergency safety measures for launching manhole covers" based on the principles of "locking dangerous areas, delimiting hazard levels, and completely eliminating hidden dangers based on the hazard level and existing capabilities. Specifically, it includes replacing the decompression type anti-fall manhole cover, setting up a camera to monitor the status of the manhole cover, setting a ladder in the sewer to escape from falling pedestrians, establishing a manhole cover information and damage monitoring system, etc.

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