I recently had the honor of being a presenter on the speaking program for the Electric Cities of Alabama Engineering and Operations Conference, held near Birmingham from 10/17-10/19. This opportunity was at the invite of one of Electromark’s sales agents Utility Specialists, Inc., serving multiple states in the South Eastern US. I felt the main takeaways of that presentation worthy of sharing here.
The driving standard is the NESC, which is adopted as code in full or part by most states. What the NESC requires for fenced or walled enclosures without a roof is fairly simple and straightforward; a safety sign shall be placed beside the door at each gate or entrance, and a safety sign shall be displayed on each exterior side of a fence or wall enclosure.
Aluminum is always a great performing material for the price, is offered by many manufacturers, and is probably the most commonly spec’d material for outdoor sign applications. But I often hear utilities express valid concerns over theft due to the high scrap value of metals like aluminum. In fact, that is probably the main reason many utilities attach their signs behind the mesh on fenced enclosures; a practice just clarified by the 2017 revision of the NESC and now specified to be installed on the exterior side. The example pictured above right is improperly positioned behind the fence mesh, obscuring the safety message. Where theft is prevalent, I recommend considering other long lasting but still cost effective materials having scrap value that is insignificant and obvious enough so as to be a recognizable disincentive to theft. Alternate materials having limited/no scrap value include Electromark’s polycarbonate or fiberglass signs; which can also offer greater weathering durability over aluminum.
Wide openings of chain link fence present a challenge to using commonly available nut/bolt/washer combination hardware. I recommend protecting your sign investment by using the application-specific fence clip brackets that are offered by Electromark and many other manufacturers. These generally function by providing a larger bearing ‘washer’ surface than spans an entire fence link opening. These clips can be purchased with tamper resistant one-way screws, corrosion resistant materials, and offer the convenience of allowing installation by a single person without even needing to enter the enclosure in order to attach the sign.
Signal Word Choice
I frequently see instances where many utilities in a well intended effort, default to the DANGER signal word because it represents the highest level of seriousness; in the belief that no matter where utilized it will then cover all circumstances. But one of the main intentions of the ANSI Safety Sign standard is to limit the proliferation of DANGER only to circumstances where it is warranted, in order to avoid conditioning towards lax meaning among the public and workers due to its being used in situations that represent a much less serious hazard than DANGER might otherwise imply. DANGER indicates imminent hazard; you are in a position where there is direct exposure to energized parts. WARNING indicates a potential hazard; you are safe where you are, but if you go beyond the barrier with the WARNING sign you will be in danger. This makes WARNING the appropriate header word choice to use on signs posted on the outside of perimeter fences or walls.
As previously stated, code only requires a safety sign at each entrance and each side of an enclosure. But one sign per side of your substation enclosure may not be enough protection. This may be especially true where the length of the enclosure is particularly long and the distance or viewing angle from certain locations may not be adequate to be able to read the message. Larger letter characters can be read from greater distances; character height relative to safe viewing distance is specified in ANSI Z535.2. But readability of a sign significantly deteriorates at angles of more than 60 degrees from the perpendicular to the sign face. These are factors that should be considered so that the sign message can be read from a safe viewing distance at all approach angles to each side of an enclosure. The NESC Handbook notes that in general practice, signs spaced at between 2 and 3 times the determined safe viewing distance have proven effective. Further elaboration and guidance on this can be found in Appendix B of the 2017 NESC companion handbook.