A manhole cover, also known as a maintenance hole cover is a removable lid over an opening that is enough for a person to pass through and the opening access is normally used as an entrance to the underground drainage system and other underground chambers. Manhole is required for people to clean, inspect, or repair the subsurface utilities when necessary. The manhole cover is used to keep safe by preventing anyone from falling into the manhole and keep unauthorized people out of it. It has to be at least a minimum of 22 inches and a maximum of 60 inches in diameter. The average weight of a manhole cover is ranging from 113kg to 136kg. Manhole cover must be made of strong and heavy material such as cast iron, galvanized steel, ductile iron, or combining of these materials to keep the safety. The manhole cover is available in different shapes, sizes, designs, levels of strength, and finishing processes. We should pay attention when choosing the type of manhole cover in order to provide efficiency and effectiveness with the use of manhole cover.
The Manhole cover is made of cast iron which means the cast iron is melted, and then poured, cast into a mold. All castings are made in foundries. The manufacturing process of a manhole cover consists of five steps which are pattern making, mold preparation, melting/pouring, cooling, and finishing. There are three main types of manhole cover in the market. Firstly, the Ductile Iron Manhole Cover which is the most common type of manhole cover as it is reliable and solid. The ductile iron will not be easily corroded and stronger than other cast iron materials. Secondly, Recessed or Screed Manhole Cover is a special manhole cover that is suitable for laying paving block, screed, or any type of infill in order to provide a great decorative finish which is the same as the surrounding pathway design. It will only be leaving a few millimeters of the frame that is visible. Thirdly, the Solid Top Manhole Cover is made of galvanized steel and normally used for lighter application as it is light in weight. The manhole cover is also classified by its weight and each suitable for different applications. Below is the weight classification and the application:
A15 - Sidewalk and cycling area
B125- Light traffic and driveway duty
C250- Car park. Suitable for slow-moving vehicles and areas
D400- Heavy traffic such as main roads
E600- Heavy duty areas like warehouses, docks, etc. For solid tyres vehicles such as a forklift.
F900- Airports. For high wheel loads.
When choosing the manhole cover for the manhole, it is understandable to apply a manhole cover that exactly fits in the manhole or larger than the size of the manhole. The manhole cover is measured in its clear opening size which is equivalent to the size of the chamber. For instance, a manhole cover listed at a size of 600x450mm will have an overall measurement of around 650x550mm and it is designed to fit a hole at a size of 600x450mm. It is important to choose the correct size that fits the hole as if too small the manhole cover will likely fall. In addition, there will have holes inserted in the manhole cover for lifting up the cover. If you would like to increase the safety of the manhole, you can also insert a locking mechanism into the cover. Normally we will find marking on the manhole cover to indicate the type of service under it or what’s accessible in the manhole without the need to open it, for example, a remark of sewer system/foul water (FW), natural gas firm (GAS), telecommunication firm or subway service, etc.
There are multiple types of manhole seals available such as single seal, double seal, or No seal. Most of the manhole cover has a single seal which can be either sealant or neoprene strips. The single seal is sufficient for creating an airtight seal. The Double seal is providing a doubling effect on the seals above and create a comprehensive airtight seal. This can reduce the pressure handled by the seal and prevent air from escaping. The double seal is suitable for internal sewage manholes, foul drainage manholes within the buildings. No seal is also known as ‘plain seated’ which is normally used for access to utilities, cable system where there is no smell coming out from the manhole. No seal is the most cost-effective type as there is no airtight seal and only has a slot which can put the cover on top of the frame,
When replacing the manhole cover, you are also required to replace the frame together as it is difficult to source a new cover that fits perfectly with the existing frame. Manhole cover can be seen everywhere, from roads, parks, driveways to the warehouse and provides access to the underground system for cleaning and maintenance works. It is important to select the right size and weight for the manhole cover and its frame. MecHero Malaysia supplies different types and applications of the manhole cover to meet your industrial requirements. You can always contact us at +6011-7000 7687 or email us at my.mechero@gmail.com for the inquiry about the manhole cover in Malaysia. We also supply a wide range of steel material, hardware, or mechanical components. Tell us your requirements now and we can advise you accordingly.
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