A complete ductile iron manhole cover and frame set mainly consists of three parts: The cover body, the load-bearing frame (manhole ring), and the sealing gasket.
The cover body is made of high-strength ductile iron, with its strength and toughness improved through a spheroidizing process. Its thickness is typically between 2 and 10 mm, and it is the main load-bearing structure. The load-bearing frame (manhole ring) is also made of ductile iron and is used to fix the manhole cover and transmit pressure to the manhole opening. The sealing gasket is usually made of rubber or other elastic materials with excellent oil, water, and aging resistance. It is located between the cover body and the manhole opening to prevent rainwater and debris from entering the manhole.
The thickness of ductile iron manhole covers is designed according to the usage environment, with standard thickness (approximately 60 mm) and reinforced thickness (approximately 80 mm). For example, a 700 mm diameter manhole cover corresponds to a manhole ring with an outer diameter of 800 mm.
The materials used for cast iron manhole covers mainly include gray cast iron, malleable cast iron, ductile iron, and alloy cast iron. Ductile iron is more durable and robust than gray cast iron.
