Transmission tower structures present unique challenges towards materials and attachment methods used for asset identification and hazard message warning signage. This is due to the difficult and remote accessibility of these structures, and the fact that there is wide variation and no standardization in the form these structures may take.
Before we discuss challenges or mounting options, let’s identify the types of signage we might need to attach to a transmission tower. It is often desired or required to mark towers with different signage and at multiple locations on a single tower. Signage for ground-level viewing purposes is often attached at about 10 ft. above ground so that it is easily viewed, but just out of reach in order to prevent theft, tampering, or defacement. This signage typically includes a 14″ x 10″ or 20″ x 14″ ANSI conformant “Do not climb” or falling hazard type warning message on readily climbable structures carrying supply conductors which are adjacent to roads or areas where people may regularly travel or gather as required by code.
Separate structure identification number signs include ground view markers using characters between 2.5″ and 6″ in height, and identification number signs for aerial inspection and maintenance purposes using characters between 6″ and 12″ in height attached at or near the top of every 5th or 10th tower.
Challenges
Transmission towers are typically widely spaced structures that traverse remote areas over vast distances; where sign condition and replacement is more difficult, expensive, and impractical to monitor and execute. Therefore it makes sense to utilize only materials that provide the best weathering durability, up to the expected life of the tower if possible. These materials include metalphoto®, fiberglass, porcelain, and certain specialty character engraved or imaged plastics.
Towers may be constructed of wood, steel, aluminum, fiberglass, or even combinations of these materials utilized for different structural components comprising a single tower. This means that no one system of direct fastening may be possible or appropriate. In some instances it is not desirable to drill and tap threaded holes directly into certain materials due to creation of potential points of corrosion or stress, and may be difficult to execute in the field. With metal towers, and especially those without flat mounting surfaces, welded mounting attachments would need to be compatible with specified signage, and therefore fail to be an incorporated design element during fabrication of the tower structure.
Towers may be lattice construction, mono-tower, or hybrid. As well, structural members comprising the tower can be widely varied in cross sectional dimensions, and have cross sectional profiles such as angle shape extrusion, tubular, or polygons having any number of sides. Again, this means that no one system of direct attachment may be possible, and systems of indirect, adaptive attachment dedicated to a specific profile shape will not work with other shapes.
Finally, the structural tower member to which the sign is attached, especially with lattice towers, may be a vertical, horizontal, or angled part of the structure. As well, where attachment to adjacent structural components may be necessary, these components may not be arranged parallel or square to one another. This presents a challenge as signage typically is designed with mounting holes that align in some sort of a square grid or in-line arrangement.
Solutions
Electromark offers a universally adaptive solution in the form of a stainless steel bracket clip with a threaded boss and bolt/washer hardware. This eliminates the need to drill and tap holes into the tower structure, or to have welded bosses in pre-planned locations that holes in signs have to be designed to line up with. The bracket can be positioned in any location to line up with mounting holes in the sign, and mounts to almost any shape including tubular structures, using industry standard high tensile strength stainless steel banding. Banding is attached using a standard and commonly available tensioning and fastening tool.
But some applications still require a custom engineered solution because 3rd party contractors have their own specifications, or the tower structure or desired mounting location still can’t be utilized with an adaptive mount or other standard solution. And yet other times a unique type of sign is required or the tower already has integrated, dedicated, and unique mounts intended for signage. In these instances Electromark has custom capabilities, and is prepared to work with utility engineers or third party construction contractors to provide engineered solutions.
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