Photo provided from the Damage Prevention Professional Library
Beneath our feet is a maze of underground assets we rely on each day. Sewage pipes, gas pipes, water pipes, and electric cables that form the very infrastructure on which we stand.
Most of us remain relatively unconcerned about these underground amenities. Someone’s taking care of them—right?
Yes, the utilities industry is aware of these assets and does keep tabs on them, but this is no easy task. The assets are, after all, underground.
And it’s not as though utilities personnel are equipped with x-ray vision. Throughout history, to simply locate specific assets these individuals have had to rely on ancient paper records and inexact location technologies.
Until now, at least.
At last, the technology has emerged to take much of the guesswork out of underground asset detection. But before we get to that, let’s go through the options utility workers have to choose from.
Tracer Wire and Electromagnetic Locators
Tracer wire, also called locating wire, is a sturdy, generally copper wire (or other corrosion resistant wire like stainless steel) that aids in the detection of plastic pipes and any other types of underground lines that are not otherwise detectable. When a plastic pipe is first buried, tracer wire is buried with the line.
When the asset needs to be located, a utility employee can use an electromagnetic locator to find an electromagnetic transmitter attached to the wire directly or by electromagnetic induction coupling. The locator can trace a low frequency LF radion "trace signal" transmitted on the wire and therefore at the approximate location of the tracer wire (and thus the asset).
Advantages—Tracer wire is perhaps the longest standing electronic tool in underground asset marking. Utility companies have been relying on the method since the 1950s and it has proven effective over the years.
The wire is easy to install, plus the price is relatively low and has remained somewhat stable over the years.
Disadvantages— There are some risks and unknowns with this technology. Wire is sturdy, but not unbreakable. Given time, the material can corrode and the wire may break. There is really no way to guard against this, and if the wire does break, the technology is nearly useless.
But the major issue with this technology is that the "trace signal" can "jump" to a nearby buried wire or metal pipe. This can lead the user in the wrong direction and to wrong location conclusions. For this reason, wire tracing requires some training and experience and is often called a "skill" or an "art" by industry professionals.
GPS is a satellite based navigation system. Using incoming signals from satellites above the earth, it provides users the approximate location of a target.
Depending on the reception quality from the satellites and the sensitivity of the GPS device, locations can be three to five meters or even sub-meter. "Survey grade" GPS devices used by professional land surveyors are even more precise.
Advantages—GPS makes the invisible visible in the form of a map. You don’t have to try to picture whereabouts an asset is underground; the tool maps this area for you. It is easily obtained and universally accepted.
Disadvantages—The main disadvantage of GPS is that it is not capable of pinpointing the exact location of an asset. It will get you within a few feet or yards of your target, but the rest is guesswork.
If you have to rely on GPS alone, you’ll likely be unnecessarily digging a lot of holes before you find the asset point.
Short for ground-penetrating radar, GPR uses radar pulses to image underground assets. It transmits high frequency radio waves into the ground and records returning signals to map buried features.
Advantages—Like GPS, GPR is valuable in that it provides a visual representation of underground structures. It is also fairly simple to use.
Disadvantages— The tool is limited by the electrical conductivity of the ground. In areas where soil conditions are poor (clay for example), it may not be able to return a full image. The image is also difficult to interpret without proper training. Think of an ultrasound picture that is only wavy lines, for example.
A GIS (Geographic Information System) map is essentially a database of geographic and geospatial information. Data (generally from remote sensing and other data sources) is entered into the system and it returns a detailed map of an area. Different types of data form different map layers.
Advantages—GIS maps provide a great deal of information. They can show all assets at once and in relation to one another. They also serve to store all information on these assets and make this data readily available to all.
Disadvantages—GIS maps are in computer or paper form. They can thus be lost, damaged or for some reason not available in the field when needed.
Because humans enter data into the system, it is subject to user error. This tool is also limited in that it provides information on assets but cannot pinpoint their location when the user is actually in the field.
A magnetic locator is a device used to detect underground magnetic fields at or near buried assets. As its name suggest, the locator hones in on the magnetic field of steel and iron objects and energized electric power lines. It sounds a tone or gives an indication on a meter when held over a magnetic asset.
Advantages— Magnetic locators are perhaps the easiest to use and most cost-effective buried asset location tool. They can pinpoint the exact location of a magnetic asset.
Magnetic locators can be used in a variety of ways; they can easily detect cast iron manhole covers and valve-box lids that have been paved over or the joints in buried steel pipelines, for example.
Disadvantages—A magnetic locator is only useful when in proximity of a magnetic asset. Magnetic locators cannot detect plastic pipes or non-magnetic metals such as copper, aluminum and stainless steel.
A Better Solution: Underground Magnetic RFID
RFID, or radio-frequency identification, is a new technology that uses the synergy of precise magnetic location and a radio frequency interrogation of an RFID chip and a unique response to gather and update information in the field about various assets.
Magnetic RFID markers for buried utilities are a 3-in-1 tool. They serve not only to magnetically mark accurate location of buried assets, but provide important information about the location and a paperless way to update the GIS database on information about them in the field.
The wireless magnetic RFID technology requires no power source. The data on the RFID marker can remain with the asset indefinitely, reducing future labor costs. Underground magnetic RFID is a time saving method that permanently preserves the exact location of an asset and provides information and verification of the asset point.
To learn more about the InfraMarker, Berntsen’s all-in-one underground RFID marking system, visit the InfraMarker product page or request a catalog.