The mass of these circular metal coverings found in streets and sidewalks varies considerably depending on their composition and intended use. Typical examples range from lightweight versions around 50 pounds to heavy-duty versions exceeding 250 pounds. Factors influencing this weight include the diameter of the cover, the material (cast iron, ductile iron, composite materials), and the anticipated load requirements. For instance, covers in high-traffic areas or those designed to support heavy vehicles are significantly heavier than those located in pedestrian zones.
A substantial weight is crucial for several reasons. It prevents displacement by traffic or accidental impacts, ensures the cover remains securely in place, and helps to mitigate theft. Historically, the weight has been a byproduct of the chosen material, cast iron, offering inherent durability and strength. However, modern material science is exploring lighter, yet equally robust alternatives to reduce manual handling risks and improve overall efficiency.
