Manhole Covers

manhole covers

This standard establishes the load classes, materials, construction and test principles, the marking and quality control of gully tops and manhole tops with a clear opening up to 1000 mm, for installation within areas subjected to pedestrian and/or vehicular traffic, and divided into six distinct parts:

• Part 1: Definition, classification, general principles of design, performance requirements and test methods;
• Part 2: Gully tops and manhole tops made of cast iron;
• Part 3: Gully tops and manhole tops made of steel or aluminium alloys;
• Part 4: Gully tops and manhole tops made of steel reinforced concrete;
• Part 5: Gully tops and manhole tops made of composite materials;
• Part 6: Gully tops and manhole tops made of polypropylene (PP), polyethylene (PE) or unplasticized polyvinyl-chloride (PVC-U).

Part 1 sets forth the general requirements that all devices made of any type of material must fulfil. Plus, depending on the type of material they are manufactured with, the manhole tops and gully tops must meet the specific requirements in Parts 2 - 6.

In 2017, all manhole top and gulley top manufacturers implemented EN 124:2015 by voluntarily applying the new certification schemes, issued by independent, accredited certification bodies, pursuant to EN ISO 17065.

In order to provide the market with guidance on the application of the standard, the Italian manufacturers and the UNI standardisation body have drawn up a technical specification UNI/TR 11671:2017 'Gully top and manhole covers - Guidance for the application of series EN 124:2015'.

The EN 124:2015 series of standards has not yet been published in the Official Journal of the European Union, so currently the CE marking and the drawing up of the DoP (in accordance with Construction Products Regulation No. 305/2011) are not applicable to these products.

Based on EN 124:2015, the following information must be applied in a clear and durable manner on each cover, grating and frame:

• reference standard (e.g. EN 124-5 for composite manhole covers);
• appropriate load class (for example B125);
• manufacturer identification name and/or trademark;
• place of manufacture, also expressed as a code;
• date or week and year of manufacture.

As mentioned above, as compliance with standard EN 124:2015 is voluntary, the manufacturer who obtains a product certification, issued by an independent accredited certification body, must include the marking of the body who issued this certification in a clear and durable manner on each cover, grating and frame.

The official documentation, for example the certificate of conformity, issued by the certification bodies, must include the product designation indicated below, as required by the standard:

• name of the product;
• reference standard (e.g. EN 124-5 for composite manhole covers);
• load class (for example B125);
• type of material (for example C2 for composite material);
• section number of the standard EN 124:2015 of reference for the cover or frame (number 5/5 indicates that the cover and frame are in composite material). Conformity of covers and frames made with two different materials is accepted as long as the requirements of EN124:2015 are met (for example composite covers and cast iron frames);
•  clear opening in mm (DP);
• type of securing method (for example with closure F);
• skid resistance (for example raised pattern RP).

In order to certify a manhole cover, it must pass and comply with the tests laid down in EN 124:2015 part 1 as well as the part of the standard referring to the material it is made of.

The tests must be carried out by an internationally recognised certification body and listed in the certificate of conformity.

Correct installation is essential to guarantee long life and efficiency of all construction products, therefore including manhole covers. Incorrect installation of the manhole covers, regardless of the material they are made of, can have harmful or even dangerous effects for the integrity of pedestrians and vehicles. The manhole covers must be installed by properly trained and qualified personnel, using appropriate equipment.

The manhole cover must always be in the class appropriate to the place of installation and therefore to the stress to which it will be subject. If in doubt you must use a device of a stronger class than that strictly foreseen. The designer must also choose a size appropriate to the clear opening to guarantee safe access.

Furthermore, before installation, the following indications must be checked:

• the manhole cover must be appropriately marked with reference to the standard (EN124) and to the certification body which issued the certification marking;
• the frame must have the same shape as the pit on which it will be placed and the clear opening must be similar to that of the pit;
• the size of the frame must be less than or equal to the depth of the housing so that, when the job is done, the frame, cover and paving are on the same level. It is preferable that the depth of the housing chamber be 2 to 4 cm higher than the frame to be able to make a concrete bedding which guarantees correct distribution of the loads on the support surface.

As for the choice of material for the bedding, if the road is closed off during installation, cement mortar with characteristic compressive strength (R_ck) greater than or equal to 50 N/mm² can be used, respecting the curing times prescribed by the manufacturer.

If the road needs to be opened to traffic quickly, the manhole covers must be placed on materials for quick hardening installation with the following minimum features:

• maximum grain size of the aggregates: 4 mm
• density of fresh mortar; 2300 kg/m³ – 2600 kg/m³
• volumetric increase in 1 d: + 0.5%
• workability time: ~15 min
• compressive strength:
  • after 30 min ˃ 1.5 N/mm²
  • after 1 hour ˃ 8.0 N/mm²
  • after 24 hours ˃ 35.00 N/mm²
  • after 28 days ˃ 50.0 N/mm²
• characteristic compressive strength of the material at the end of hardening: ˃50.0 N/mm²
• lasting performance durability and consistency
• resistance to salt and freezing
• impermeability to water
• absence of chlorine

When the level of the manhole cover housing on the pits needs to be raised, a shimming material can be used with a minimum compressive strength of 50 N/mm², it must have lasting durability and be compatible with the installation materials intended to be used.

Shimming materials are generally made of cast iron, steel or concrete. It is not allowed to use hallow bricks, broken tiles, pieces of wood or plastic or anyhow any type of material which does not provide the necessary strength and durability features.

The contracting company performing the job first of all must make sure that the pit, prefabricated or built on site, is intact and capable of structurally bearing the weight of the manhole cover to be applied.

It is also essential to make sure that the frame and the installation seating on the pit are clean by eliminating any traces of mud, grease or debris. If necessary, the top of the pit could be roughened to improve the hold of the laying material.

The depth of the housing chamber must be made taking account of the height of the devices to be installed, to avoid using shimming materials as much as possible. The width of the housing chamber must be at least 1.6 times the maximum external size of the frame of the device to be installed, so that a consistent and uniform concrete kerb can be made around it.

It is recommended to mix the laying material mechanically and not by hand so that it is homogeneous: the operation must be carried out as quickly as possible and anyhow before quick hardening.

Immediately after applying the laying material, the frame must be positioned promptly at the correct height, centring the clear section of the frame with that of the pit and exerting appropriate pressure on the bedding to guarantee a firm grip, making sure that no internal part of the frame overhangs the pit. The frame must not be positioned directly on the top of the pit.

The frame must be positioned on the bedding so that its bearing surface is appropriately supported by the top of the pit/chamber. When installing the cover in the presence of heavy and/or frequent vehicular traffic, it is recommended to anchor the manhole cover frame to the concrete slab or wall of the underlying concrete pit, positioning the fastener plugs in the specific circular slots in the frame. Furthermore the frame must be positioned at road level using appropriate reference points and so that it is level with the surrounding surface.

Make sure there are no empty spaces between the manhole covers and pit; pay special attention when applying the laying material near the cover seating so that residual material cannot deposit. It is also necessary to make sure that the laying material covers the flanges of the frame with at least a 1 cm width and comes out of any holes or slots on the frame, providing a perfect grip.

Beddings thicker than 4 cm should be applied at two different moments: the first layer should be 2 to 4 cm thick, while the following layer should only be applied after having placed suitable primer material in between. Make sure to leave sufficient residual thickness for the finish of the road surface. The exposed surfaces of the bedding, both inside and outside the frame, must be smooth and made even.

The manhole covers must be inserted carefully into the frame only after the material has a sufficient grip and compressive strength and only after a careful check and cleaning of the support surface of the seal and of the seating of the frame where the cover must be inserted.

The finish filling around the manhole cover must be carried out after at least 3 hours with the same laying material, leaving a layer of at least 3 cm to allow the finish of the road surface by laying asphalt. Make sure no compacting devices pass over the manhole cover to avoid damaging the bedding/frame/cover system. The installation must not be subject to any type of stress until the bedding material has reached sufficient strength. After installation, the frame and cover/grating must be level with the road surface.

Before opening the area where the manhole cover is located to traffic, the curing times supplied by the manufacturer of the product used must be respected: if there are no different indications, it is necessary to wait at least 72 hours.

KIO Composite manhole covers                            How to choose a manhole cover

One of the main features of

• use of materials with a specific weight lighter than that of cast iron, though obviously guaranteeing the strength features required by the standard;
• study of the geometry of the manhole cover optimised depending on the particular production method.

This makes it possible to make the system consisting of cover and frame weigh considerably lower than other products found on the market.

We are given a comparison expressed in kg between the weight of the frame + cover system made of composite material and the weights of the frame + cover system made of grey cast iron and ductile cast iron by European manufacturers. The weight difference is on average beyond 70% compared to covers in grey cast iron and beyond 65% compared to covers in ductile cast iron.

The low weight considerably reduces operators’ risks during handling, installation and subsequent maintenance of the manhole covers. Law Decree 81/08 (Consolidated Act on Health and Safety at Work) defines the maximum permitted weight for handling loads on construction sites as 25 kg. The weight of composite manhole covers up to model 600x600 C250 is below this limit. Even smaller cast iron manhole covers require the intervention of two persons and the use of mechanical equipment for handling and installation.

Composite manhole covers                            Modular manhole covers

strength class;

shape;

dimensions;

components.

There is no legislation establishing the shapes and dimensions that manhole covers must have, so production rules are dictated by the market and customer needs.

• rectangular – 900x500 to 1000x558 mm
• square – 300x300 to 950x950 mm
• round – Ø425 to Ø1230 mm
• square grid – 500x500 mm

Characteristics of manhole covers                            KIO Composite manhole covers

Composite materials are the combination of at least two components, chemically different one from another, characterised by chemical-physical properties which cannot be found in the individual materials making them up. In particular, compared to traditional materials, composite materials are at the same time sturdy and lightweight, have ideal resistance to corrosion and chemical agents and a high thermal and electric insulation capacity.

Glass fibre is one of the most well known reinforcing materials, widely used for the production of composite materials. Common experience tells us that monolithic glass is very fragile due to the great number of crystallisation defects which act as micro fractures and stress concentration areas. Whereas if glass is spun to diameters lower than microns it loses its fragile property becoming a material with high mechanical resistance and resilience: these features are maintained even at very high temperatures.

The family of composite manhole covers includes, for example, fibreglass manhole covers, while plastic manhole covers do not. Composite manhole covers have countless advantages over manhole covers already on the market made of cast iron or concrete.

The main features are:

• LIGHTWEIGHT AND EASY TO HANDLE

One of the main characteristics of composite manhole covers is their light weight.

The weight difference is on average beyond 70% compared to covers in grey cast iron and beyond 65% compared to covers in ductile cast iron.

The low weight considerably reduces operators’ risks during handling, installation and subsequent maintenance of the manhole covers.

• RESISTANCE TO CORROSION AND TO CHEMICAL SUBSTANCES

The manhole cover in composite material is not subject to corrosion or to the attack of chemical substances: in fact the superficial part of the cover is fully built in thermosetting resin, resistant to acid and alkaline substances, oil, grease and hydrocarbons.

This feature, in conjunction with the impossibility of generating sparks or condensate, make the manhole cover in composite material especially suitable to be used in fuel dispensing plants. By now it is common practice worldwide to use manhole covers in composite material instead of cast iron in these plants.

Corrosion resistance is also particularly important in industrial and civil sewerage networks, especially in the case of weak slopes: the gases generated inside pipes and manholes do not corrode the lower part of the manhole cover.

Lastly, we emphasise the resistance of the thermosetting resin to salt water, a characteristic which makes the use of manhole covers in composite material especially suitable near the sea.

All of these features make it unnecessary to paint the manhole cover in composite material, unlike those in cast iron.

• NOISE LIMIT

Thanks to the property of the raw material used, use of a cover and frame in composite material reduces the noise of traffic or pedestrians passing over, typical of cast iron systems and due to an imperfect coupling between the cover and frame or caused by installation errors.

• ELECTRIC AND THERMAL INSULATION

The outer surface in thermosetting resin makes the manhole cover a perfect insulating system, making stray voltage impossible, thus protecting pedestrians from the possibility of accidental electric shocks due to uncovered electric wires.

The manhole cover is also a low heat conductor: for practical purposes, this behaviour can be important where for example there are hot steam leaks in remote heating networks.

• PERMEABILITY TO ELECTROMAGNETIC FIELDS

Manhole covers made of composite materials are more permeable to electromagnetic fields than those made of both spheroidal and lamellar cast iron. Thanks to this feature, multiple applications are possible:

- Sewer systems: a level sensor placed below a composite manhole can monitor and control the level of effluent inside the manhole. An anti-intrusion sensor can also be combined with this technology in order to detect tampering, forcing or removal of the manhole cover;

- aqueduct networks;

- transport systems: the manhole cover can be used as a cover for electronic devices that control and manage the circulation of trams, trains and metros.

• RESPECT FOR THE ENVIRONMENT

Two main factors weigh in favour of manhole covers in composite material compared to cast iron manhole covers as to the emission of CO₂ into the air:

- energy necessary to reach the fusion temperature of the raw material to be cast inside the moulds of cast iron manhole covers (beyond 1200°C) and the operating temperature of the moulds for composite materials (around 60°C)

- reduced weight of each individual piece making it possible to load 3-4 times more manhole covers than normal cast iron manhole covers on a trip thus reducing pollution due to fewer number of transports.

• THEFT PREVENTION

The theft of manhole covers is aimed at selling them for metal remelting. Aside from the economical damage, these thefts have extremely dangerous consequences as they leave dangerous openings on the road which are not signalled.

The theft of composite manhole covers (wrongly called plastic manhole covers) is unattractive since there is no illicit secondary market.

KIO Composite Manhole Covers                            Composite Applications

For the success of a project, it is important to know how to choose the right

The designer must also choose a size appropriate for the clearance to guarantee safe access to the manhole cover with manhole. As far as the shape is concerned, generally the Italian market of grids and underground works have the widespread presence of square shapes (starting from the outside dimension of the 300x300 frame), rectangular and circular shapes. Fuel service stations and purifying plants have manhole covers with outside dimensions exceeding 1 m.

Furthermore, before installation, the following indications must be checked:

• the manhole cover must be appropriately marked with reference to the standard (EN124) and to the certification body which issued the certification marking;
• manhole cover - manhole are to be understood as a single item, in that the former is to be installed above the latter. The frame of the manhole cover must therefore have the same shape as the device underneath;
• the height of the frame must be less than or equal to the depth of the housing so that, when the job is done, the frame, cover and paving are flush. It is preferable that the depth of the housing chamber be 2 to 4 cm higher than the frame to be able to make a concrete bedding which guarantees correct distribution of the loads on the support surface.

KIO Composite Manhole Covers                            Discover the features of manhole covers

Let’s start with the definition of manhole cover. It is nothing more than the cover that is placed over manholes, through which one may inspect, when necessary, what is underground (

Manhole covers come in different shapes and materials, but when it comes to choosing which type to use, one must take into account mechanical strength, durability and the net clearance of the opening.

When we talk about mechanical strength, we are referring to the class that characterises each manhole cover. The choice depends on the area of use, which is divided into 6 groups according to the EN 124 reference standard. Each group is assigned a resistance class that must be complied with:

• Group 1: areas that can only be used by pedestrians and cyclists. The most suitable manhole cover is class A15;
• Group 2: pedestrian areas and similar, lay-by areas or multi-level car parks. This is the B125 class area;
• Group 3: for gully tops installed in the area of kerbside channels of roads which, when measured from the kerb edge, extend a maximum of 0.5 m into the carriageway and a maximum of 0.2 m into the footway. This group is assigned class C250;
• Group 4: carriageways of roads (including pedestrian streets), hard shoulders and lay-by areas, for all types of road vehicles. The class allowed by the regulations is D400;
• Group 5: areas of imposing high wheel loads, e.g. aircraft and port pavements. The manhole cover to be used will be class E600;
• Group 6: areas of imposing high wheel loads, e.g. aircraft pavements. The only class allowed is F900.

With regard to durability, one must consider many aspects, including the material of the manhole, the area in which it is to be installed, the temperatures and fluctuations to which it is subjected, and the frequency of traffic.

The clear opening is the diameter of the largest circle that can be inscribed in the net cross-section of the frame, basically the net clearance of the manhole. This value is normally unique for all manhole cover manufacturers. The element which is not subject to particular specifications is the outside dimension of the cover and above all the outside dimension of the frame. Therefore, each manufacturer may have different thicknesses and outside dimensions of the cover, making it impossible to interchange the covers.

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