Based on its class, we can distinguish cast iron manhole covers into two types, namely heavy duty manhole covers and medium-duty manhole covers. While in terms of design, heavy-duty manhole cover type has the same design with medium duty manhole cover type. Some are square, round, hinged, and without hinged. Then what are the differences between medium-duty and heavy-duty manhole covers?
4 Differences Between Medium Duty Manhole Covers & Heavy Duty Manhole Covers
The first difference between the two types of the manhole cover is the strength or weight of the load that can be sustained. Medium-duty manhole covers designed to withstand light loads vehicles, such as family cars and pickup cars. While heavy-duty manhole covers designed to withstand heavy loads such as airplanes and container trucks.
In the use of manhole cover, it is important to adjust the strength with the burden that often overrides it. If not strong, manhole cover can break when the vehicle passes.
We usually make heavy-duty manhole covers from the ductile iron material which is the top grade of cast iron. Ductile iron has the following advantages:
- Not easily cracked or broken
- Able to reduce vibration
- Able to withstand high loads
- Spheroidal graphite
- Stronger than white cast iron
While the medium-duty manhole covers usually we make from a grey cast iron material. Grey cast iron is able to withstand light loads. The properties of grey cast iron are:
- Able to reduce vibration
- Lameral graphite
- Not easily broken, bent or pierced
- Low elongation
We can also make heavy duty manhole covers from grey cast iron, provided we have to design them thicker than medium-duty types. Thus manhole covers still able to withstand high loads.
3. Location of use
In term of usage, heavy-duty manhole covers are often used in areas that are passed by heavy vehicles such as airport areas, power plants and gas stations. The projects that have used heavy-duty manhole covers are Mass Rapid Transit (MRT) of Jakarta, Bali Airport, and Asahimas Power Plant.
While the medium-duty manhole covers are usually used in areas that passed by light load vehicles such as residential areas, offices, pedestrian zone, and sanitation projects.
In terms of price, heavy-duty manhole covers are more expensive than medium-duty manhole covers. This is because the ductile iron material has a higher price than grey cast iron. Besides heavy duty manhole covers has a heavier weight compared to medium duty manhole covers if both are made from grey cast iron.
In choosing the type of manhole covers, you need to adjust it to the type of load that passes through it. So that the manhole covers are not broken because it is not strong enough to withstand the loads. For areas where heavy vehicles often pass by, you should use a heavy duty manhole cover. Whereas for areas where light load vehicles often pass by, you can use a medium-duty manhole cover.