Manholes cover is a removable plate that is used to shield the manholes from anyone or anything from falling into it. Different manhole cover sizes, types and standard classes are explained in this article with respect to the code BS EN 124: 2015.
Types of Manhole Covers
The three main types of manhole cover as per BS EN 124: 2015 are:
- Ductile Iron Manhole Cover
- Solid Top Manhole Cover
- Recessed or Screed Manhole Cover
1. Ductile Iron Manhole Cover
This type of manhole cover is solid and reliable. It is one of the most common types of manhole cover. This type of cover does not corrode easily and are highly brittle in nature. The Ductile iron cover is stronger compared to the cast iron material. The different classes of ductile iron are specified based on the specification given in BS EN 124: 2015.
2. Solid Top Manhole Cover
These are galvanized steel manholes which are basically light in weight. These manhole cover has a fitting flush at the ground level and has inset grab handles. These are employed for lighter use. BS EN 124:2015 specifies the weight classes for the solid top covers.
3. Recessed or Screed Manhole Covers
These are special manhole covers that have the provision to lay paving block or screed. This hence facilitates great decorative finish for the driveways.
Specification of Manhole Cover
The size specified for the manhole cover is stated as the clear opening of the manhole. A manhole of size 600 x 450mm has a greater size including its frame. It is always advisable to employ a manhole cover that exactly fix the manhole or greater size. A smaller size could fall in.
The manhole cover is placed over a metal base. There is a small rim that fits the cover. As the base and the cover are mostly made by casting process, it is called castings.
The covers have "pick holes" with a handle to lift the manhole cover. These pick holes are sealed to make the cover watertight or it can be left as such to let sunlight pass through it.
The manhole covers may sometime have certain markings that indicate the type of services under it, like if it is a sewer system or water system or telecommunication firm or natural gas firm or subway service, etc.
Weight Classes for Manhole Covers
Different weight classes for manhole covers as per BS EN 124: 2015 are mentioned below in figure-2.
Where,
A15 = Pedestrian and cyclist Utility
B125 = Occasional light traffic and driveway duty
C250 = Slow movement of cars and vans( For example in car parks)
D400 = Main road traffic-fast moving traffic
E600 = Heavy duty traffic like in warehouses, docks, etc. Movement with solid heavy tyres
E900 = For areas with heavy duty loads eg. In airports
Note: The numbers designated in each class represent the withstanding load in kilo Newtons. For example, a class of C250 means, the manhole cover can withstand a load of 250Kn.
Also Read: Materials Used for Manhole Construction