What are cast iron manhole covers? What is its function? We will discuss it here.
The drainage system is one of the important aspects of the development of each city or region because it is related to other aspects such as health, beauty, and traffic in the city. If the drainage system is bad, it can cause flooding which will have an impact on public health, cause congestion, even make the city look dirty.
Manhole covers are covers for access hole at drainage, sanitary, and sewer channels. The access hole serves as a way in and out of workers when cleaning or repairing drainage channels. The hole needs to be closed to prevent people or anything falling to the channel.
While cast-iron manhole covers are manhole cover made from cast iron material. Cast iron materials for making manhole covers are grey cast iron and ductile cast iron.
Types of Manhole Covers
Cast iron manhole covers have several types that we can distinguish based on the shape, size, and strength or resistance to the load through it.
Based on shape
- Square manhole covers
- Rectangular manhole covers
- Round manhole covers
Of the three forms, the round manhole cover is the best because it has several advantages including:
- Its strength is better because it has no residual stress. This residual stress spreads on all sides of the circumference.
- It’s easier to open or close, and won’t fall when you open it by turning. Unlike a square manhole cover that can fall when you open it diagonally.
Although a round manhole cover is better than a square manhole cover, for some projects it is more suitable to use square manhole covers such as a pedestrian path or sidewalk project. Pedestrian paths generally use square-shaped ceramics, so using square manhole covers will be more matching.
Based on size
- Manhole cover 400: Consists of 400 mm in diameter round manhole covers and 400×400 mm square manhole covers
- Manhole cover 600: Consists of 600 mm in diameter round manhole covers and 600×600 mm square manhole covers.
- Manhole cover 700: Consists of 700 mm in diameter round manhole covers and 700×700 mm square manhole covers.
- Manhole cover 800: Consists of 800 mm in diameter round manhole covers and 800×800 mm square manhole covers.
- Manhole cover 900: Consists of 900 mm in diameter round manhole covers and 900×900 mm square manhole covers.
- Customized manhole cover: Manhole cover beyond standard size. Manhole cover size as needed at the project site.
Based on the strength or load passes
- Light-duty Manhole Covers: a manhole cover type for use in areas that do not pass through any load or only light load such as humans and bicycles.
- Medium-duty Manhole Covers: a manhole cover type for use in areas where only light to moderate loads pass, such as motorbikes and MPV cars.
- Heavy-duty Manhole Covers: manhole cover type for use in areas where heavy vehicles often pass such as container trucks and airplanes.
We use grey cast iron to make light-duty and medium-duty manhole cover types. Meanwhile, to make heavy-duty manhole cover types we use ductile iron. Ductile iron material is the highest grade of cast iron (Grade A) which has advantages over grey cast iron material. Therefore ductile cast iron is suitable for making heavy-duty manhole covers.
The Process of Manufacturing Cast Iron Manhole Covers
1. Design
The process of manufacturing manhole covers begins with drawing designs by the engineering team. Engineers use 2D and 3D drawing software and simulation software. From the results of the design, we can find out the shape and weight of the manhole cover that we will manufacture. So we can also estimate the raw material requirements for producing manhole covers.
2. Pattern
The results of the design drawings are then applied to a pattern. Usually, we use wood and aluminum to make patterns. We use a wood pattern when manufacturing manhole covers in small quantities. While the aluminum pattern we use when manufacturing manhole covers in large quantities.
3. Mold
The wood or aluminum pattern is then applied to a mold. This manhole cover mold uses Sand Molding and Resin Bonded Sand Molding. Sand has the characteristic of being able to absorb heat so that the casting product can immediately cool and form.
4. Melting
Melting is a crucial process. Here we melt the raw material in the melting furnace with the temperature reaching 1300° C. After the raw material has melted, then we will pour it into the sand mold that we have prepared before.
5. Finishing
The finishing stage consists of shot blasting, grinding, and painting. Shot blasting is the process of cleaning the sand that is still attached to the manhole cover. Grinding is the process of smoothing the surface of the manhole cover. The painting is a process of the coloring manhole cover to make it look better.
6. Quality Control
The final process in manufacturing cast iron manhole covers is quality control. This process aims to ensure that product quality meets the standards. Quality control consists of:
- Ensure the dimension suitability
- Chemical composition test
- Mechanical properties test
- Physical properties test
Projects that use cast iron manhole covers
Every building that has a drainage channel must use drainage components to support its function. Projects that often use manhole covers include:
- Airport
- Road and pedestrian path or sidewalk
- Hotel
- Apartment
- Power Plant