Manholes are a valuable construction element that provides several functions. They enable maintenance workers to gain access to telecom lines and underground pipes. Additionally, they serve as access points for meters that quantify the flow of liquid in the effluent pipes.
Manholes have to be covered using manhole covers to shield anything or anybody from falling in the manholes and keeping out unwanted materials and unauthorised persons.
The Different Types Available
Manhole covers are available in different materials and designs, each one offering a set of different benefits and features. Here are the three types of composite manhole covers:
BMC (Bulk Molding Compound)
Bulk Moulding Compound or BMC is a form of composite material intended for the manufacture of BMC lids. The components used to make these covers consist of steel bars, trasys, calcium carbonate, glass fiber, and unsaturated polyester resins.
The technique of production is simple and inexpensive. BMC lids have a uniform colour similar to plastic and have a smooth surface.
SMC (Sheet Molding Compound)
Sheet Molding Compound or SMC is also a composite material that is used for the manufacture of SMC lids. Elements used to manufacture these lids are trasys, calcium carbonate, glass fibre, unsaturated polyester resins, and some additive.
The technique used to manufacture SMC lids is a bit complicated and expensive than that of BMC covers.
FRP (Fiber Reinforced Plastic)
Fiber Reinforced Plastic or FRP is by far the best composite material for manufacturing lids. It has components such as quartz, glass fibre, unsaturated polyester resin, and some additives.
The technique of making them is a bit complicated compared to SMC or BMC lids.
Alternative Manufacturing Materials:
Because of the maintenance and engineering problems associated with cast iron manholes, alternative manhole cover types have increased in popularity in the past couple of years including fibreglass, plastics, and composite materials.
Some of the main advantages of plastic manhole covers, fibreglass manhole covers, and composite manhole covers include:
Lightweight – The lightweight design of composite covers makes them easier to maneuver and reduces worker injuries.
Corrosion Resistant – Another reason for the popularity of plastic, fibreglass, and composite cover and frame is that they don’t corrode like ductile iron models.
Don’t Contain Scrap Metals – With manhole theft on the rise as a result of the scrap metal value of conventional ductile iron models, many cities are looking for alternative materials that don’t have any scrap value.
Keep Out Storm Water and Inflow – While ductile iron covers have a loose fit, covers crafted from fibreglass, plastics and composites have a more secure fit with a seal, which, in turn, keeps out pollutants.
More Secure – Drain covers can be fitted with security systems that will keep them locked in place, avoiding unintentional removal, theft, and tampering.
Manhole Covers Weight Classes
Weight classes for manhole covers are as follows:
Very light duty for pedestrian areas such as driveways, patios, and gardens
Ideal for occasional light traffic with domestic driveway thresholds
Perfect for lightly trafficked areas with slow-moving vans and cars
Suitable for heavily trafficked areas, highways, and main roads such as public car parks
Recommended for heavy-duty areas like warehouses, loading bays and industrial estates
Extreme heavy-duty applications such as airports and docks
Over the years manhole covers wear off, they become weak because of a lot of exposure to the elements. They’ll eventually break, especially if they’re made of ductile iron.
Broken covers allow drain odours to leak from underground drainage systems and are risky for vehicles and pedestrians, so they must be replaced.
Here are the key factors to consider when buying replacement covers:
All manhole cover manufacturers use a similar technique to measure their covers: They are classified by their clear opening size, which is the size of the opening that they’re made to conceal.
For security reasons, it’s imperative that replacement covers are fit for the purpose they are intended, and this boils down to the areas that the covers are to be fitted, and the traffic in the area.
Plastic, Iron or Steel?
As long as you stick to the guidelines as mentioned above, the decision is yours. Traditionally most covers were iron made, but with modern-day advanced technology, the options are unlimited.
Galvanised steel covers are easily installed and lightweight but can be rated up to 17 tonnes, so they are trendy and versatile. On the flip side, iron and plastic covers and frames are dark, so they’re perfect for tarmacked driveways. Once you find out the correct weight loading capacity and size the choice is yours!
Plastic Inspection Chambers
For those who own new properties, there is a high probability that the manhole covers might be on top of plastic inspection chambers as opposed to brick manholes.
In such instances the width of the chambers must be measured, placing a tape measure across the inside – it’ll most likely be round. Then all that is required is to buy covers and frames to suit the size of the chambers (usually 450mm).
Another thing to keep in mind is that you still have to ensure your cover is of the correct weight class when mounted on a plastic chamber!
Block Paving and Patios
A Recessed cover is just a metal tray that lets you lay out a slab or block paving inside to match the surrounding area. Usually made from galvanised steel they are also available in different loads and sizes, so if you’re having your driveway block paved, replace your cover around the same time - just ensure that your recessed cover is of the right weight class.
Once the correct cover and frame have been sourced a builder or other capable person should install it. The frame should be bedded in concrete and levelled correctly. The concrete should be allowed to cure for at least three days before any weight is put on to the cover frame.
Can a square cover be fitted into a circular chamber?
Yes, there’re a few covers that are round to square, meaning they’ll fit in round or square chambers. These covers include the 300SR, and the T1G3, to name a few.
Why did a forklift break my heavy-duty manhole lid?
Well, a forklift has rock-hard wheels, which exert pressure differently to typical pneumatic, so your cover frame must be specifically designed to suit this.
How do I know the size of cover I need?
All manhole cover sizes are measured by the clear openings inside the frames, as this is the only true constant between manufacturers’ designs.
I have the correct measurements of my clear opening size, but I can’t find a match, why?
This is because your manhole cover is old-fashioned and in imperial measurements. However, we can provide custom-made solutions with covers made to the exact specs you need.
Can you give me any pointers on the installation process?
If you’re still hesitant after reading this comprehensive guide, feel free to get in touch with us.
I need access through my manhole covers regularly, is this possible?
Of course, most covers have inbuilt lift keys. However, the best way to get easy access is to order custom-made, hinged covers.
How does an access cover differ from a manhole cover?
Since they’re very similar products, most folks find themselves wondering what the difference is. Well, each has its own unique advantages and can be used for a range of different purposes.
Manhole covers are generally used to securely and safely hide the entrance of drains and other chambers. They're often made from concrete, galvanized steel, ductile iron or cast iron or even a combination of several of other materials.
On the flip side, access covers are usually found on internal floors, driveways, car parks, foot ways, pavements, and roads. Their purpose is to protect pedestrians from falling in man-made holes and providing workers with access to underground services.
Why are manhole covers circular?
Some possible explanations include:
A Circular cover doesn’t have to be rotated or precisely aligned when placing it on the opening.
A Round casting is much easier to make using a lathe.
It’s easier to dig circular holes.
Round covers can be easily rolled or moved.
Unlike square covers, round covers cannot fall through the circular openings, whereas square covers could fall in if they were installed diagonally.
Is anti modern slavery part of your policy terms conditions?
Yes. We’re dedicated to ensuring that there is no trace modern slavery and human trafficking in our supply chains or any part of our business.
What is damp proofing?
Damp proofing is a general term that covers treatments and techniques employed to prevent damp from being absorbed through floors or walls into the interior of a property.
Order Manhole Covers at EasyMerchant Today
Here at EasyMerchant, we keep a wide range of Manhole Cover and frame intended for any application including inspection chambers and surface boxes. We have all load capacity ratings from domestic all the way up to F900 for use in docks and airports. We also have all thicknesses and sizes carefully chosen from the leading manufacturers and brands in the industry today.
To view the products in this category simply visit the sub-category pages above, we keep most sizes including 450mm, 600mm, 600 x 450mm and lots of major brands such as Eccles, Naylor, Clark Drain and more.