Manufacturers & Procurement

At the Bahrain manufacturing facility... the heavy plate metal covers suffered from deformation and corrosion.  They were replaced with Fibrelite’s GRP trench covers (right).

At the Bahrain manufacturing facility... the heavy plate metal covers suffered from deformation and corrosion. They were replaced with Fibrelite’s GRP trench covers (right).

Fiberlite solutions meet market, project needs

March 2020

In response to increasing demand for radio frequency (RF)-friendly manhole covers, UK-based composites manufacturer Fibrelite has developed a new range of manhole access covers designed to support data transfer between antennas underground and aboveground.

One of the primary current uses of RF/smart manhole covers is as part of (real-time) remote underground monitoring systems/telematics in utilities, where transmitters under covers are used for monitoring and/or control of oil/water usage, sewer flow, floodwater and similar. Other industries adopting these include mining and telecoms (for example, 5G signal boosters).

“Traditional ductile iron and reinforced concrete manhole covers aren’t conducive to the transmission of RF signals,” explains a spokesman for Fibrelite. “Metal reflects the signal, while concrete greatly weakens it (exhibits high attenuation coefficients). This means that the transmitted signal is greatly weakened, restricting range and functionality. Glass-reinforced plastic (GRP), in contrast, absorbs far less of the signal. 

Fibrelite’s new RF manhole cover, the FL60RF draws on the low properties of GRP and includes a thin structure in the middle of the cover to contain the antenna – further lowering the attenuation of the signal without compromising the strength or deflection properties of the cover.

Tested at the University of Lancaster on behalf of Fibrelite, the new FL60RF showed far lower attenuation compared to a 2-mm-thick aluminium plate and passed the load-bearing test EN 124 C250 (now certified to C250 - 25 tonne) load rating.

Fibrelite is a global manufacturer of highly-engineered GRP composite access covers that can take loads of up to 90 tonnes whilst still being light enough to be lifted by hand.

Initially developed almost 40 years ago and now an industry standard for petrol station forecourts, Fibrelite covers are increasingly specified for both new and retrofit work in a variety of industries in more than 80 countries around the world.

In the region, Fibrelite has provided retrofit solutions for two industrial facilities in Bahrain.  Its trench covers have been used to replace corroding metal covers at a manufacturing facility in the kingdom, where heavy chequered plate metal covers had been installed over an underground interceptor. The interceptor was in a heavily trafficked area used mainly by heavy goods vehicles (HGVs) and other support vehicles. The facilities manager required a replacement trench covering solution that would be capable of supporting loads of up to 40 tonnes while allowing safe, fast removal by site maintenance teams.

 The previous covers had been loaded beyond their elastic limit and as a result suffered from permanent deformation. In addition, the covers suffered from corrosion and were beginning to break down.

The specifying engineer was familiar with Fibrelite’s products from a previous project and reached out to the company for help in solving this issue.

Fibrelite’s GRP trench access covers can support the heavy loads without permanent deformation. Its GRP manhole covers are also corrosion-resistant and lightweight, allowing for easy manual removal, delivering a maintenance-free solution.

All Fibrelite trench covers can be safely removed and replaced manually by two people even at F900, using the FL7 lifting handles (at all load ratings).

Covers were manufactured and delivered to the local contractor within the tight construction schedule and provided a long-term solution for the client.

Fibrelite’s GRP trench covers have also been installed at a Bahrain support facility, where trench access covers were needed for two service ducts within the workshop. The previously installed steel covers had permanently deformed under heavy operational loads, resulting in the covers being unstable.

A solution was required to support loads of up to 30 tonnes while being able to be safely and quickly removed by operatives to provide access to the duct for routine maintenance.

 “The challenge with this installation was twofold,” explains the spokesman. “Firstly, the previously installed steel covers lacked the necessary reinforcement to resist the operational loads. Secondly, the existing trench recess had an uneven depth resulting in excessive rocking of the covers.

“The specifying engineer found Fibrelite via an online search and provided a detailed brief of the project and design parameters.  Using these, Fibrelite provided a retrofit solution, custom engineering and manufacturing its GRP trench access covers to suit the client’s requirements. The Fibrelite trench covers that were installed have a load rating of 30 tonnes and are corrosion resistant and therefore will have a longer lifetime than the previously installed metal covers,” the spokesman says.

A custom aluminium frame was installed to improve the stability of the covers, providing an even surface on which to place the new trench covers. Fibrelite’s trench access covers can be removed safely and easily by two people using their ergonomic lifting handles.   

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