Tracer wire is an invaluable tool for helping utility companies and construction crews locate underground pipes and buried assets before they dig. But tracer wire is only one piece of a complete locating solution. For the solution to function correctly, all components should meet rigorous standards and be installed according to industry best practices and published municipal specifications.
Tracer wire (aka locating wire) is an insulated wire buried with underground assets like natural gas or water lines. To locate those assets before excavating, crews employ a frequency transmitter to create a circuit along the tracer wire and a receiver to determine the wire’s location.
While tracer wire is commonly used with poly tubing and other non-conductive piping, it’s also useful with ductile iron pipes. Even though ductile pipes can conduct electricity, they’re often wrapped in polywrap or exposed to earth and grounded, making them difficult to locate.
Tracer wire is commonly available in solid copper or copper clad steel (CCS) variants. While solid copper is more flexible and the traditional choice, CCS wire has a higher breaking strength and is lighter and more cost-effective.
With a rugged, high molecular weight polyethylene (HMWPE) insulation, tracer wire is rated for direct burial in wet or dry locations and is electrical and corrosion-resistant. Tracer wire is available in multiple gauges (usually 18 to 4 AWG) and rated for different voltages (600 volts is the most common). Finally, tracer wire is available in multiple jacket colors, each designating a specific utility (e.g., yellow for natural gas and green for sewer lines).
For tracer wire to work, it has to complete an electrical circuit underground. Electricity always takes the path of least resistance and seeks out ground, and all electrical circuits need a ground to complete the circuit.
If tracer wire isn’t properly grounded, the circuit won’t be complete, and the wire will be undetectable. Therefore, all tracer wire dead ends and terminations must be properly grounded. To achieve grounding, installers attach dead ends to grounding rods (usually made of copper, zinc, or magnesium) placed into the earth.
Tracer wire is subjected to difficult environmental conditions, both underground and at termination points. Over time, copper wire ends can corrode at underground splice points and above ground terminations. Purpose-built, waterproof connectors can help preserve the integrity and performance of tracer wire for many years.
Connectors are typically made with molded polycarbonate to resist cracking from impact or temperature changes. The connector housing has a locking mechanism to securely fasten the tracer wire ends, while the corrosion-proof inner housing protects the wire termination or splice.
When an electrical current passes through a tracer wire, it creates a radio signal. Using the ‘active method,’ utility crews attach a locating transmitter to the tracer wire to generate the current and use the hand-held receiver to sweep the surrounding area to locate the wire. The alternative ‘passive method’ uses only the receiver to detect currents already present in cable and power lines.
Transmitter units are built to generate different frequencies and provide greater flexibility in locating a range of underground assets. Low frequencies (512 Hz) are best for finding tracer wire, while higher frequencies are better for locating assets like telecom cables or jointed pipes.
Access points provide above-ground or grade level termination sites for tracer wire and also serve as grounding points. Designed to protect wire terminations and resist corrosion, access points should be well marked and color-coded for each specific utility.
To ensure optimal equipment performance and job site safety, it’s critical that crews correctly install all locating solution components. Contractors and utility operators should focus on three elements to achieve the best results:
Training and Certification. Many municipalities, utility companies, and wire and component manufacturers partner to provide training and certification for installing locating solutions. Completing this training helps contractors deliver consistent, professional results.
Following Industry Best Practices. Training helps to promote valuable best practices for installing locating solutions, including proper tracer wire placement and burial, connector installation, and post-installation inspection and testing.
Understanding Local Specifications. Most cities and municipalities publish detailed specifications for installing tracer wire and other locating components. Successful contractors work closely with local authorities to understand the specs and clarify any uncertainties throughout the installation process.
It’s not easy for contractors and utility providers to install high-performance, long-lasting locator solutions. It takes choosing the right components, proper training and certification, and close collaboration with local authorities. However, the benefits — reducing costly repairs, service disruptions, worker injuries, and even fatalities — surely justify the extra efforts.
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