With the significant investment of the country in new infrastructure, urban renovation, upgrading of public facilities, laying of wires and cables, etc., the demand for manhole covers is constantly increasing, which inevitably leads to quality inspection problems. The procurement of manhole covers for municipal engineering inevitably requires comprehensive consideration

Construction requirements:

1. Use ductile iron, and the raw materials for making manhole covers should comply with the provisions of GB1348. The rainwater grate is made of ductile iron QT500-7 2. The styles of manhole covers include square ductile iron manhole covers and circular ductile iron manhole covers, which can be selected according to the actual engineering situation. The selection of rainwater grates is based on the design 3. The embedding depth of the manhole cover: The embedding depth of the heavy-duty inspection manhole cover should not be less than 40mm. 4. The height of the protrusion that the manhole cover should have should not be less than 3mm 5. The manhole cover and rainwater grate should be made flat and smooth with the surface of the support, and there should be no cracks or defects such as cold insulation or shrinkage that affect the performance of the inspection manhole cover. Repair welding is not allowed 6. The assembly structure dimensions of the manhole cover and support should comply with the requirements of GB6414, and the tolerance level should not be lower than the provisions of GB6414-86CT10, and ensure the interchangeability of the manhole cover and support 7. Machine the contact surface of the manhole cover and the support surface of the support to ensure smooth contact between the manhole cover and the support 8. The bearing capacity of the manhole cover shall not be less than 360KN, and the allowable residual deformation shall be 1/300 * D. The bearing capacity of the rainwater grate shall not be less than 140KN 9. Galvanized chain connections or other forms of locking devices should be used between the manhole cover and the support. The grate and well ring can be connected through a pin (or other form), and the overturning angle of the grate is not less than 120 °. The anti-corrosion method for the grate and well ring is to apply one coat of asphalt varnish

Inspection items

Material inspection types: gray cast iron, ductile iron, cast steel, rolled steel, polymer, filling reinforcement materials, steel fiber concrete, etc.

Appearance inspection: surface quality, defect inspection, contact surface quality

Structural dimension inspection: anti slip pattern height, concave convex area, elevation, slope, embedding depth, total clearance Well seat support surface width

Well seat quality inspection: bottom support pressure, height, adaptability, net opening