球墨铸铁井盖等级标志设置场合轻型Q 禁止机动车进入的绿地、甬道、自行车道或人行道普通型P 汽10级及其以下车辆通行的道路或停放场地重型Z 机动车通行的道路或停放场地井盖是用来掩盖道路上或家中深井的防御物，用来防止行人或物体坠落。
Nodular cast iron manhole cover grade mark sets the occasion light Q prohibit vehicle into the green, corridor, self lane or ordinary sidewalk type steam P level 10 and the following vehicle road traffic or parking space heavy Z motor vehicle traffic road or parking site covers is used to cover up the matter on the road or in a deep well of defense, to prevent pedestrians or objects falling.
Generally divided into circular and square in downtown road, usually circular, because round manhole cover is not easy to incline to better protect the pedestrian and vehicle safety. Using the circular, mainly considering the circular covers through the center of each diameter length is the same, so if the manhole cover by the passing vehicles rolling, because no matter how to roll, the diameter will be slightly wider than the below the wellhead, the manhole cover will not fall to the wellhead.
And if the square. Because of the diagonal of the square was significantly longer than that of each of its sides. Such covers are rolling, easily along the wellhead in the diagonal direction fell into the wells, resulting in potential safety problems.
If the wellhead made into round or significantly less than the cover, will not fall into the well covers square. Here is the problem of the maximum use and saving of a material.
Wellhead are used depending on the size of wellhead, if you want to install it on top of an area is far greater than the square manhole cover for a wellhead, then the utilization and practical value of the material no natural directly using the circular covers more effective, not only save covers material, but also to ensure the safety of wellhead。 While in the countryside and the use of cable wells, generally square, so that it can better prevent the rain and other liquids into the。
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