Photo provided by Michael Twohig from the Damage Prevention Professional Library
Perhaps one of the most tried and true methods of locating subsurface utilities involves utilizing a simple signal and receiver system with conductive tracer wire and an electromagnetic locator.
The basic principle behind this method centers on the alternating currents within an electromagnetic field, which are detected by utility workers above ground to locate the general position of a buried utility.
Because many assets are constructed of materials that naturally generate alternations in electromagnetic currents, tracer wire is primarily used on utilities, which are non-conductive. These include lines made of polyethylene, plastic fiberglass, concrete, and other non-conductive materials.
Utility companies, public agencies, and utility contractors rely on devices equipped with electromagnetic pipe detection (EPD) technology to pick up on the signals transmitted by the charged tracer wire. At that point, utility companies can employ a variety of excavation techniques to access the buried assets for service.
The Shortcomings of Electromagnetic Location Systems
Although this method has become a very common practice within various utility industries, the potential disadvantages of this system should be taken seriously when deciding what sort of technology should be utilized to mark and track a specific network of subsurface utilities.
Before examining the problems inherent in electromagnetic locating, it’s important to note that such a system has enjoyed a generally favorable track record since its introduction during the mid-1950s, and continues to be installed in utility works all over the country.
Perhaps most advantageous to utility companies is the relatively low cost of electromagnetic equipment when it comes to installation. Additionally, many utility location crews already have some version of the cable locator system on the truck.
With this being said, there are some major flaws with this system, which vary in severity depending on the specific environment of the utility system in question.
First, it’s important to consider the material being used. A common metal used for tracer wire is copper, due to its high conductivity.
While this metal is generally reliable in unstrained environments, copper itself is an expensive material which has been prone to theft. Copper tracing wire is rapidly becoming a favorite and readily available commodity traded for cash at scrap yards.
And unfortunately, once this utility asset is pulled out of the ground, it’s virtually impossible to trace back to the source.
Second, it’s important to consider the layout of your assets in relation to one another when deciding whether or not this system suits your needs. The trace signal is known to “jump” to nearby metal pipes or other trace wires, leading the locate technician off in the wrong direction.
If your plan involves the need for bent wires to accommodate unaligned utility positions, installing copper wiring involves a significant risk. Its inflexibility means that too much strain will almost certainly result in broken wires.
This is a hazard during both the short-term installation processes as well as long-term wear-and-tear as bent sections of wire can wear and corrode much faster than unstrained sections.
Third, the environmental impact of moisture can lead to major problems for a wire-based system, which depends on durable materials. Many wires have nylon or vinyl coatings, which can fail when the line is unprotected and subject to moisture contact.
Introducing an Innovative Alternative
Radio-frequency identification (RFID) is an innovative 21st century solution to aging 20th century utility practices.
Instead of electromagnetic locators which rely on temperamental wiring and corrosive materials that are bound to deteriorate over time, RFID equipment gives utility companies not only a more physically-reliable system of marking and locating subsurface assets, but can also provide more than just the asset point location. RFID provides detailed information about the nature and precise asset point location of such utilities.
Think of it like a string of Christmas lights lit using the two different circuit types. In older light designs, stringing each light in series with one another meant even one lamp’s failure to light meant a total systemic failure throughout the circuit.
Likewise, a system of tracer wires requires multiple nodes of assets to operate in continuous perfect harmony. Any failure in the string results in total system breakdown and significant financial headaches for contractors and utility companies when it comes to locating, servicing and repairing damaged utilities.
RFID systems are comparable to today’s Christmas lights strung in parallel circuits. Each node, while still part of a bigger system, receives power independently of other nodes and failures can be localized.
Equally important to consider are the advantages that RFID provides which electromagnetic locators aren’t even capable of.
While the old system of tracer wire only provides a means of approximately locating buried utilities, RFID can give utility companies and contractors a paperless way to map utility information on their integrated GIS databases. Eliminating paperwork errors is a very good way to increase productivity.
Furthermore, the problems of longevity are solved by the passive nature of RFID technology. Data remains stored in the RFID memory of the underground markers indefinitely, reducing costs associated with maintenance and upkeep found in older systems.
All together, the long-term advantages of RFID technology have proven themselves as less and less an “alternative” and more the primary consideration when deciding which system will provide the most cost effective results.
To learn more about the InfraMarker, Berntsen's all-in-one underground RFID marking system, visit the InfraMarker product page or request a catalog.