Telecom systems (excluding fiber optic cables) don’t normally require tracers because the locate signal is applied to the conductor sheaths. However, many principles mentioned in this article still strongly apply.
Tracer wire is specially designed to be buried near non-metallic pipes and cables. Some examples are fiber optic cables, poly pipe, fiber glass pipe, PVC pipe, Fiberspar pipe, and more. This is done to provide an electrical path so less expensive conventional locating methods can be used to locate otherwise difficult-to-locate utilities. Hopefully the wires are installed in close proximity with the utilities they are intended to protect. Undoubtedly tracer wire plays an extremely important and necessary role in the continuing effort to minimize preventable damage to our infrastructure.
Poor understanding of standard line locating basics and sloppy, outdated construction methods are causing thousands of mis-locates every year. Sadly, most people are still following the bad practices of the past. As underground utilities become more crowded, it’s time for serious change. New technologies exist today to fix most of the problems of the past.
When locating wires, tracers or telecom, low frequency should be a locate technician’s first choice. It creates a small, compact signal which is less likely to transfer to unintended targets. This translates into cleaner, more accurate locate results. It does, however, require direct connection points and far-end grounding (the far end of wire locates need to be grounded).
Higher frequencies don’t require far-end grounds but they create very large, intense signals which readily transfer to unwanted targets, and are not optimum, particularly in congested areas. The locate technician can become easily confused resulting in bad marks that lead to unnecessary damage and serious consequences. In short, using higher frequencies in congested areas is a terrible practice that needlessly creates confusion and bad locates.
If you spent any time in the field you have seen tracer wire ends hanging free or lost in the weeds. (Figure 1) This is a mistake for two reasons – not only are they subject to environmental damage but they remain ungrounded as well, forcing locate technicians to use high frequency in order to overcome the lack of far-end grounding.
Permanently grounding wire ends is also a bad practice! Grounded ends need to be easily interruptible in order to provide isolation preventing the transmitter’s energy from simply traveling to the best ground rather than following a pre-determined path. Also, it is extremely important to make sure all line segments are easy to separate from one another and the ground simultaneously. This is a tremendous improvement over the past!
With these two measures in place, a locate technician can now design their own path and accuracy and efficiency are dramatically improved. Fortunately, specialized, retrofit systems are available that solve these problems with the flip of a switch. (Figure 2) No more lost hardware or frozen fingers fumbling with poorly thought-out connectors.
Sloppy, outdated construction methods continue to sabotage our infrastructure damage protection measures. Many are still building in stumbling blocks that cannot be easily rectified. For instance, when tracer wires “wander” in a ditch or are stretched around corners, they end up too far away from the utilities they are intended to protect. (Figure 3) Remember, a locator’s signal follows the tracer, not the actual utility. Consider how often you have seen construction crews install tracers poorly. They must be installed with regard for function.
For best results, tracers should not be closer than 2” or farther than 6” from the utility. Never wrap them around or tape them directly to the utility. (Figure 4) They should never be allowed to contact the utility. (Figure 5) The utility could be damaged if lightning or stray electrical current accidentally finds its way onto the tracer. (Figure 6) They should be held in place with spacers at the 5 o’clock or 7 o’clock positions if possible. This puts them in the “shadow” of the pipe which helps to minimize damage from backfilling and subsequent excavations while remaining close enough to achieve accurate locates.
If tracer insulation is damaged and left unrepaired it will corrode forcing the use of high frequency to overcome any breaks. In order to overcome less obvious insulation nicks, small magnesium anodes can be used as grounds. They make excellent grounds and help protect tracer wires from corrosion due to insulation damage.
Never tie your system to foreign grounds. Since it’s impossible to know what foreign grounds are tied to, this practice will definitely create impossible locating nightmares. Signal will go in many different directions simultaneously creating unbelievable confusion. Use your own, independent grounds for your system.
After locates are complete, all tracers and locate wires should be bonded together and grounded at termination points along the system. This does three things:
1.Allows a locating tech to start any place on the system with the assurance that the farend is grounded
2.Helps protect wires from lightning and stray electrical current
3.Makes wires much more visible to passive locating.
Never use standard electrical wire (THHN or THWN) for tracer wire installations. They are not designed for it and will fail prematurely. Tracer wire is specifically designed for the task. It is covered with a thick high density or high molecular weight polyethylene insulation (HDPE or HMWPE) which is designed for the harsh environments and is unbelievably tough.
Never use conventional splicing methods for tracer wire. They often exist in extreme environments and require special care. Splice kits specially designed for this purpose are available from many suppliers.