Sewer fiberglass manhole cover

Types of sewer fiberglass manhole cover

Steel and iron manholes traditionally replace these materials with more modern and lighter sewer fiberglass manhole covers.

Self-Contained manhole cover

This is the type of sewer fiberglass manhole cover that has a self-contained buoyancy provision. Cached equipment that drains the sewer through pumps or other means is housed in these manhole covers. Such covers are well suited for sewer systems in low areas prone to flooding. It helps to prevent collapse due to buoyancy as well as an influx of water. The buoyancy mechanism is generally a hollow ring seal encased by buoyant foam, so even if the water level rises inside the sewage system, the cover will not budge from its position.

Mechanically fixed manhole cover

This type of reinforced manhole cover comprises a mechanically attached buoyancy component. Examples of these buoyant parts are ropes and chains. Such covers are typically found in manholes of sewage systems that do not experience frequent inundation with water. The main role of such a cover is to inhibit the cover from flying off during flooding.

Ventilated manhole cover

Ventilated fiberglass manholes are meant to relieve the buoyancy that fiberglass covers trap. These covers are created with perforations or vents intended to promote gas exchange between inside the manhole and the outside atmosphere. This practically eliminates buoyancy issues because the gases that cause buoyancy are aired out. These covers are ideal for sewer systems that potentially hold gas, such as methane.

Unventilated manhole cover

This type of cover is the most commonly used type due to the absence of a buoyancy release vent. Even though this type conserves gas and does not let it out, it can also be dangerous because that very gas leads to buoyancy. Unventilated manhole covers are not meant to be used in manholes with high gas concentration.

Access manhole cover

This type of fiberglass manhole features a hatch or opening, providing easy access to the interior of the sewer system. With tools and equipment, maintenance and repairs can be easily carried out. Access manhole covers come in handy for joints, lateral connections, and other parts of the sewer system that require regular maintenance.

Industry applications of sewer fiberglass manhole cover

Fiberglass manhole covers have great resistance to corrosion, as well as their light weight properties. They have several uses in industries located in places where the manholes are prone to flooding or highly acidic.

Chemical processing

Chemical plants produce highly corrosive substances such as acids and solvents which can damage metal manhole covers. Fiberglass manholes are resistant to chemical corrosion and are therefore suited for this environment. These plants also experience frequent spills and sludge accumulation and thus need covers with good resistance to that. In addition to the above features, fiberglass covers are also lightweight; hence, they are very easy to remove.

Wastewater treatment

Wastewater treatment plants create a lot of gases, such as methane and hydrogen sulfide, which can be dangerous. That is why it is best to use ventilated concrete manholes in these places to relieve the gases. Wastewater treatment plants also face the possibility of flooding, resulting in the buoyant (and not very useful) steel or iron manhole covers surfacing. Because of the buoyancy mechanisms incorporated into the fiberglass covers, flying away cover is not an issue.

Marine facilities

Any industry situated by the water, be it a shipyard or a port, has to deal with the realities of corrosion. Since salt water is the most popular culprit of corrosion, it is better to use fiberglass manholes resistant to its effects. These industries are also prone to flooding, so a lightweight and buoyant cover makes it easy to handle the manholes.

Landfills

Landfills create gases such as methane, which can accumulate in manholes and even become explosive. That is why ventilated fiberglass covers are the best solution for this environment. Landfills also produce highly acidic leachate, which can corrode metal covers over time. Fiberglass covers are durable and resistant to acid, making them ideal for this job.

Product specifications and features of sewer fiberglass manhole cover

Technical specifications

• Material: Fiberglass reinforced plastic (FRP) or glass-reinforced plastic (GRP)
• Load Class: Usually conforms to international standards like EN 124, AASHTO, or AS 3600. Specific load classes rangefrom A 15 to C 250, depending on local requirements.
• Size: Standardized diameters often range from 600 to 1200mm but can bemade to order for custom applications.
• Temperature resistance: Generally from -40°C to 70°C but can vary based on specific resin formulations.
• Corrosion resistance: Exceptional resistance to chemicals, saltwater, and adverse weather conditions.
• Weight: Significantly lighter than traditional materials, often 50% or more lighter.

Features

• Durability: The fiberglass in concrete makes them exceptionally strong and resistant to cracking and corrosion.
• Weight: The lighter weight compared to metal covers allows for easier handling and installation.
• Corrosion resistance: They do not rust and can withstand harsh chemicals and saltwater.
• Non-metallic construction ensures they do not conduct electricity, providing an additional safety measure against electrical hazards.
• The smooth surface inhibits sediment build-up and allows for better water flow.

How to install

• After excavation, the manhole is set on a stable base, usually concrete.
• The manhole cover is then evenly placed on top, ensuring proper alignment.
• Using even pressure, the cover is securely bonded to the manhole with a sealant along the edges.
• The bond is reinforced by wrapping agreed sealant around the cover's perimeter, preventing debris intrusion.
• Post-installation, the cover is tested by applying designated weight to ensure it meets required safety standards.

Quality and maintenance of sewer fiberglass manhole cover

• Visual Inspection: Regular checks on the cover for cracks, surface wear, or visible damage. Look for signs of corrosion or lingering chemicals.
• Structural Integrity: Ensure the cover is securely bonded to the manhole; reapply sealant if bonding appears weak. Check for any cover warping over time.
• Clean regularly: Keep the cover free from debris, sediment, and vegetation. Use a mild cleaner for tough stains on the cover.
• Remove debris from vents or grates.

How to store

• Avoid exposing the cover to extreme temperature conditions without rays.
• Cover the manhole with an opaque plastic cover or newspaper.
• Store in a dry area that does not have an extremely low or high temperature regime.
• Avoid stacking the cover against other heavy items that can bend or warp it.

How to test

Fiber reinforced plastic manhole covers are generally subjected to a series of standardized performance evaluations throughout their manufacturing process to determine whether they can be used effectively. The main aim of testing is to check whether such covers can hold weight, their resistance to cracking, and any deformity. Testing is also performed to check their resistance to chemicals and whether they can be used in extreme temperatures. Covers conforming to international standards like EN 124 or AASHTO are tested for bending and bearing to ensure they can handle traffic load. An additional buoyancy test checks whether floodwaters can carry the cover away in extreme cases.

Sh-how to choose the sewer fiberglass manhole cover

When embarking on a manhole cover shopping journey for concrete, there are several factors to consider to avoid buying numerous replacements in a short time.

• Resin type: It is worth asking which type of resin was used to make the fiberglass manholes to ensure it is suitable for the environment it will be used in. For instance, coastal areas will require EDS or epoxy resins to resist saltwater corrosion.
• Load capacity: Each cover must be load classed according to AASHTO or EN 124 so that the cover can withstand different weights depending on its location. Heavily trafficked roads will need a higher load capacity than rural or non-traffic areas.
• Ventilation needs: Covers with ventilation should only be considered in high-gas areas like sewers or landfills.
• Safety features: Non-slip surfaces, warning signs, and lift tools improve safety for those working around or installing the cover.
• Joint types: Its compatibility with expansion joints and other parts of the sewer system will only ensure the cover functions correctly. Standard joints are similar in size to existing maintenance joints, which makes replacement easy.

Frequently Asked Questions (FAQs) about sewer fiberglass manhole cover

Q1: Why opt for fiberglass manhole covers over traditional steel or iron ones?

A1: Fiberglass covers are much lighter, corrosion-resistant, and safer due to non-electrical conductivity, making them ideal for harsh environments.

Q2: Are they strong enough to handle heavy traffic?

A2: Yes, fiberglass covers are load-rated to handle traffic and are tested to meet standards like EN 124 and AASHTO.

Q3: How do ventilation and non-ventilation manhole covers differ?

A3: Ventilated covers have openings to release dangerous gases from sewers, while non-ventilated covers do not, often trapping gas.

Q4: How often should these covers be inspected or maintained?

A4: Regular visual inspections and maintenance should be done at least once a year to ensure structural integrity and cleanliness.

Q5: What factors should be considered when choosing a fiberglass cover?

A5: Consider the type of resin, load capacity, environmental conditions, and compatibility with existing sewer systems.