Prefabricated concrete cable trench covers, over time, can crack and crumble, which can cause a hazard for station mechanics working in a substation facility. If the covers aren't properly maintained, workers could accidentally fall into a trench and become injured.
To protect its workers, Appalachian Power Co. is replacing some of its aging trench covers with a lightweight utility trench system called Utilicover. The system, which is manufactured by GEF Inc., is half the weight of heavy concrete covers and can be lifted by one person.
One of the first Utilicover installation jobs was completed at an American Electric Power (AEP) substation in March 2007 in Broadford, Virginia. GEF provided 1,158 covers, each 24 inches wide by 35 inches long, to the site. The field crews experienced immediate benefits of the new cover system. In the course of six-and-a-half days, a three-man crew used only 12 tons of Utilicover panels to replace 70 tons of concrete covers. The project manager stated the Utilicover covers were installed more quickly by hand than the concrete covers could be removed with an excavator.
Ease of Installation
The product is fabricated using fiber-reinforced-polymer (FRP) components manufactured by Strongwell. These components are lightweight, strong, durable, resistant to corrosion and non-conductive. As such, station mechanics can install the FRP cover system quickly and easily, and reverse the process for trench access.
Unlike concrete, the panels are individually adjustable to accommodate inconsistencies in trench width. The typical trench span is 24 inches, and at that span, with a 500-lb point load at mid-panel, deflection is about 1/8 inch, which ensures cover failure is not a concern for pedestrian rating.
To ensure that the covers fit the trench spans properly, AEP worked closely with GEF on dimensional requirements. The utility wanted the covers to fit directly back into the opening, so the field crews explained what they were looking for in the product, and GEF met their specifications.
The station mechanics met with GEF on site and explained what the issues were and how they wanted the lids to work.
Installing the Product
During maintenance or construction projects, the construction crews would have to lift these heavy concrete covers to access the underground trenches at these substations to make necessary repairs or upgrades. This was not only time consuming but it also required a significant amount of lifting that stresses the back. It took two people to lift the lid for access to the cable trench. Now only one station mechanic is needed to remove or place the cover on top of the cable trench.
To install the cover, a mechanic would need to remove one that was failed, cracked or broken, and then discard all of the components. In the past, the field workers would face the possibility of a back sprain when replacing an aging concrete cover with another cover made of concrete. The Utilicover, however, eliminates these ergonomic concerns because the mechanics are installing the new material right back into the same location and the lids are easy to handle, strong and durable.
Because the system is so easy to use, AEP has received positive response from the field workers regarding the new covers. The mechanics think the product is easy to lift and lightweight. By not having to worry about crumbling concrete, they can also have a cleaner looking installation.
Kenneth R. Posey (firstname.lastname@example.org) is supervisor of the station projects engineering design standards for the power engineering section located at American Electric Power, Gahanna, Ohio. Posey is a registered professional engineer.
American Electric Power www.aep.com
Companies mentioned in this article:
Appalachian Power Co. www.appalachianpower.com
GEF Inc. www.gefinc.com