Ductile iron manholecovers is lighter than grey cast iron ones. And they have better Resistance toimpacts and shocks than grey cast iron ones.

Traditionally, manholescovers are made of cast iron. However, in the viewpoint of maintenance,frequent opening of manhole covers has to be carried out. Therefore, it posespotential safety hazard to the workers during the lifting-up process of manholecovers because cast iron manhole covers are very heavy to normal workers.Consequently, research has been conducted and ductile iron is considered as abetter choice than cast iron because it can resist the same traffic loads withlower self-weight. Moreover, as ductile iron is less brittle than cast iron,the traditional cast iron manhole covers are more susceptible to damage andthus requires higher maintenance cost.