The quality of cast iron manhole covers is not up to standard,and due to various reasons,some inferior manhole covers are used in engineering,leaving safety hazards.There are still many cast iron manhole covers that are not qualified.If it is qualified,this situation will not occur,so inspection is particularly important.Next,let's talk about the inspection standards for ductile iron manhole covers.

　　1、Appearance:No obvious casting defects.

　　2、Special tools are used to detect the diameter of the well ring,and the control range is within the size of the well cover,with a depth of 40mm.The bolt holes should be inspected one by one using a special inspection tool.

　　3、Coordination and painting inspection

　　1.The T-shaped rubber ring should be matched with the well ring.The rubber ring should be placed flat in the T-shaped groove,not too long or too short,firmly bonded,and the fit gap should not exceed 1mm.

　　2.The assembly of the manhole cover and frame should be flat,without shaking or making any noise,and the height fit between the cover and frame should not exceed 1mm.

　　3.The T-shaped rubber ring should be firmly adhered before painting,and the well cover(ring)should be evenly painted without rust spots.

　　From the experience of use,circular ductile iron manhole covers are more commonly used because they have higher safety.A circle is a shape whose diameter is equal no matter how it is measured,so no matter how much a circular manhole cover is crushed by a vehicle,because its diameter is wider than the wellhead,it will not fall off.This is also the reason why circular manhole covers are commonly used.In the application of cable wells,square ductile iron manhole covers are mostly used to more effectively prevent rainwater from entering.

　　The above is the inspection standard for ductile iron manhole covers,hoping to be helpful to everyone.