Fibrelite has developed a new range of radio frequency (RF) friendly manhole access covers.
Fibrelite has developed a new range of radio frequency (RF) friendly manhole access covers.

Composites manufacturer Fibrelite has developed a new range of radio frequency (RF) friendly manhole access covers that can support data transfer between antennas underground and aboveground.

According to the company, one of the main 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. However, traditional ductile iron and reinforced concrete manhole covers aren’t conducive to the transmission of RF signals, because metal reflects the signal, while concrete exhibits high attenuation coefficients, weakening the transmitted signal

Glass reinforced plastic (GRP) in contrast, absorbs far less of the signal (lower attenuation coefficient), Fibrelite says.

The company’s new FL60RF manhole cover draws on the low attenuation (signal absorption) properties of GRP and includes a thin structure in the middle of the cover to contain the antenna, which also lowers the attenuation of the signal without compromising the strength or deflection properties of the cover.

In tests, the new FL60RF showed 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).

This story uses material from Fibrelite with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.