Manhole Covers: Materials and Applications

Manhole covers play a crucial role in urban and industrial infrastructure, providing access to underground utilities while ensuring safety for the persons who work with them and the millions of people and vehicles that cross them daily.

The choice of material for a manhole cover significantly impacts its performance, longevity and suitability for specific environments. In this article, we look at the many varied uses for manhole covers and how this determines the material and load rating each requires.

Materials Commonly Used in Manhole Covers

Ductile Iron

Ductile iron is renowned for its strength and resilience. It offers high tensile strength, making it capable of withstanding heavy loads, which is essential for areas with frequent vehicular traffic. Additionally, ductile iron exhibits excellent resistance to impact and fatigue, ensuring longevity. Its ability to absorb vibrations makes it ideal for roadways and highways.

Galvanised Steel

Galvanised steel manhole covers are lightweight yet robust. The galvanisation process involves coating the steel with a layer of zinc, providing enhanced corrosion resistance. Their lighter weight facilitates easier handling and installation.

Polypropylene

Polypropylene is a durable plastic material known for its resistance to chemicals and corrosion. Manhole covers made from polypropylene are lightweight, making them easy to install and remove. They are ideal for areas with pedestrian traffic, such as parks and footpaths, where heavy load-bearing capacity is not a primary concern. Smaller covers such as those used for water meters and rodding eyes, are generally polypropylene.

Thought Manhole Covers Were Just for Drains? Think Again!

Manholes serve a wide variety of purposes. Some are as small as a hand, while others are large enough for a man to enter. They all have one thing in common – to allow easy access to underground systems while protecting the systems and the people or vehicles that pass over them each day.

Residential

In residential settings, manhole covers need to blend with the surroundings while providing adequate strength. Recessed covers filled with matching paving materials are popular choices, allowing them to integrate seamlessly into patios, driveways and soft-landscaped areas. Materials like galvanised steel and polypropylene are preferred due to their corrosion resistance and lightweight properties.

Commercial and Retail

These areas experience moderate to heavy foot traffic and occasional vehicular access. Ductile iron and galvanised steel covers are suitable here, offering durability and the ability to withstand varying loads. Recessed covers are also used to maintain aesthetic continuity in public-facing spaces. Additionally, some commercial areas may require access covers for HVAC ducting, underground cable transit systems and drainage networks.

Industrial

Industrial sites often involve heavy machinery and constant vehicular movement. Ductile iron covers are ideal due to their high load-bearing capacity and resistance to wear and tear. Many industrial facilities also use underground chambers to house hydraulic and pneumatic lines, fuel storage systems and chemical containment infrastructure, requiring robust and corrosion-resistant covers.

Infrastructure

Manhole covers are widely used across infrastructure; we most commonly see them in connection with water supply (water meters, stop taps and fire hydrants), underground electrical supply, gas mains,

stormwater and sewage, and telecommunications. Less-known applications include access to sewage and stormwater pumping stations.

Road and rail networks also use manhole covers to access underground cabling for lighting, traffic control and signalling systems.

Many infrastructure-related applications require manhole covers to withstand heavy traffic and dynamic loads. Ductile iron covers are preferred for their robustness and ability to endure such demanding conditions, particularly at airports and docks, where F900-rated covers are needed to accommodate the extreme loads of aircraft and cargo equipment.

Municipal

Although not yet common in the UK, district heating and cooling networks rely on underground insulated pipes to transport hot or chilled water. Smart cities are increasingly incorporating underground cable transit systems for fibre-optic sensors, automated transport pathways and robotic delivery routes. All these require access points for inspection and maintenance.

Military and Security

Military facilities and high-security locations use underground chambers for secure communication lines, blast-resistant infrastructure and concealed surveillance equipment. Ductile iron covers with tamper-resistant locking mechanisms are commonly used to ensure restricted access and enhanced durability under extreme conditions.

Manhole Cover Load Ratings

Understanding load ratings is essential to ensure safety and functionality. In the UK, manhole covers are classified based on their load-bearing capacity:

• A15: Suitable for areas with pedestrian and cyclist traffic, supporting up to 1.5 tonnes.
• B125: Designed for light vehicular traffic, such as car parks and driveways, supporting up to 12.5 tonnes.
• C250: Ideal for areas with slow-moving traffic, like residential streets, supporting up to 25 tonnes.
• D400: Used on main roads and highways, capable of supporting up to 40 tonnes.
• E600: Suitable for heavy-duty applications, such as industrial sites, supporting up to 60 tonnes.
• F900: Designed for airports and docks, supporting up to 90 tonnes.

These classifications ensure that the appropriate manhole cover is selected based on the specific load requirements of its location.

We hope this article has opened your eyes to the many ways in which manhole covers are used and the importance of choosing the right material and load rating for each application. To explore the range of manhole covers and frames offered by Drainfast, check out our website. And if you’re installing manholes, don’t forget to look at the innovative MuckStopper®!

For further details and prices, get in touch with our friendly, knowledgeable sales team today by calling 01420 555600 or emailing [email protected]