Many considerations come in to play when deciding on the type of marker to use in a pole marking system. First and foremost, the marker must do its job, i.e. it must mark the pole so that your personnel can locate and identify it, plain and simple. Any marking system must be legible under actual field conditions. A pole marking system may look great inside an office at a sales meeting, but it must function outside 24 x 7 x 365.
A marking system must also be durable under actual field conditions. The markers need to be made of a substance that will last outdoors for decades, enduring the harsh environment of ultraviolet radiation from the sun, the corrosive chemical attack of today’s pollution, the effects of temperature extremes (the freeze/thaw and dry/wet cycles), and vandalism.
A final consideration in choosing a pole marking system is the cost of its acquisition and ownership – its life cycle cost. Often overlooked, yet undeniable, is the fact that the labor and overhead involved in attaching pole markers and maintaining them far outweighs the cost of buying the markers in the first place.
No pole marker on the market is a perfect fit for all of these requirements. Those individual who must choose a pole marking system will have to endure trade-offs between legibility, durability and economy. Let’s look at each aspect in more depth.
Legibility. The human eye needs light and contrast (field and ground) in order to see, to discern objects. As we all know, vision acuity varies from person to person. In general, humans can discern larger objects better than small ones. This is true of pole markers. As a rule of thumb, a person with 20-40 vision can see a 1” tall marker from 28 feet, a 2” marker from 56 feet, etc.
During the day the light we need to see comes from the sun. Yet, as we all have experienced, the sun can be too bright at times. A flat pole marker made of a shiny substance (mylar, aluminum or reflective sheeting, for example) often reflects the sun’s rays too well, making the marker impossible to read. The solution to this problem is to look for a marker that is not flat, but made so that it contains more than one plane – that is, a marker that is embossed, stamped or de-bossed. A simple color contrast (black on yellow, for instance) on a flat surface is not enough to guarantee legibility.
At night we see less well because the strength and angle of our light source is no match for the sun. Often a street lamp, headlight or flashlight is all that we have as a source of light. Whether these sources of light are strong enough to see a pole marker is a function of the distance of the marker from the source of light and the weather conditions (clear, rain or snow, etc.). The angle between the source of light and the marker relative to our eye is also a contributing factor to how legible a marker is at a given time. The use of reflective glass beads or reflective sheeting in the manufacture of a pole marker will enhance legibility, but only if the source of light is strong, focused, and at an angle that approaches ninety degrees to the marker from the eye of the beholder. This angle of incidence, as it is called, is critical. Reflectivity is simply light bouncing back to the viewer. A six-foot tall lineman pointing a strongly focused beam of light held at eye level at a reflective pole marker that is placed at a six-foot height on a pole will have a greater chance of reading that pole marker than if he were to shine a light from waist height at a marker attached twelve feet up the pole. Too much reflectivity can result in an illegible marker, as the letter or number is surrounded by an aura that makes reading the character difficult. To read more about reflectivity click here.
Durability. Pole markers can be made of a single substance, they can be laminates/composites, or they can be printed or painted products. While plastics have been touted as the answer to society’s need for new materials, with some being advertised as “stronger than steel,” it is a fact that all plastics are polymers. Polymers are simply linked chains of monomers, and any polymer is vulnerable to UV (ultraviolet) radiation from the sun. The sun’s UV rays “cut through” the bonds of the polymer, reducing the plastic to monomeric molecules. We experience this process as fading, cracking, and the embrittlement of plastic markers.
Metal has been field proven over the last century to last outdoors without degradation from UV radiation. Steel markers rust, and brass markers are expensive. Bronze and zinc markers are easily bent and broken. Aluminum has proven itself as a material suitable for outdoor use, as it does not rust and has good tensile strength. Aluminum oxidizes upon exposure to the air, yet this thin layer of aluminum oxide actually acts as a protective layer against further reaction. To read more about aluminum click here.
Paints and inks provide contrast on certain pole markers. Both inks and paints are comprised of a pigment and other substances. When applied and dried, the pigment is bonded to the surface of a substrate material. Layers of ink are generally thinner than layers of paint, and ink’s bonding strength (its coefficient of adhesion) is less than paint. Paints themselves are of varying quality, as each of a paint’s components (from pigment to plasticizers, solvents and UV inhibitors) is an economic choice its manufacturer makes. In general, the more expensive the paint the better it lasts outdoors. Equally important factors in the outdoor durability of either a painted or inked marker are the care and skill of those who apply the paint or ink and the cleanliness of the facility in which it is applied.
Economy. As mentioned, the (fully burdened) labor cost to attach and maintain any pole marking system is far greater than the acquisition cost of the markers themselves. From this perspective one would want to specify and purchase the marking system that will last the longest and require the least amount of maintenance. Yet it is an irony of many an electric utility’s operation that initial acquisition cost and purchasing budgets are all that are considered when buying a pole marking system. (Perhaps that is why there are only three manufacturers of porcelain steel signs left in the entire United States.)
Conclusion. Given all the facts presented in the discussion above there are choices to be made. If you want reflectivity you will have to put up with a shorter field life of your marker (even 3M, the inventor and largest supplier of reflective sheeting, only guarantees its product for 7 years of outdoor use). If you want high contrast and choose a painted product, make sure the paint used is the best and that it is applied by people who know what they are doing. But realize that even the best paint will fade, for UV radiation is stronger than any paint made by man. If you want economy, go with inexpensive plastic, heat stamped markers. But realize that these markers will peel, crack and fade within a matter of a few years. If you need to assemble complex, multi character alphanumeric coded markers, then go with a slide-in system and make the markers up before they go to the field. But realize that human error and mistakes will happen and some of those markers will be wrong, and some will never get to the field.
So, what is the best marker, given all these trade-offs? Simple. It is the Premax embossed, solid aluminum letter or number, nailed to the pole with a Premax bright galvanized steel nail. The marker will stay put for the life of the pole. It is made of aluminum and will not rust, crack, fade, or become illegible. It is embossed, and it will reflect the sun’s rays or a flashlight’s beam from multiple angles: it will never blind you as a mirror does.
We have over 80 years of experience with this type of pole marker and we have made over 800 million of these markers – all of them in the United States of America.