Ordering Information:
ORDER NUMBER:  3050
DATE AVAILABLE: Winter 2007/2008

Printed Report		PDF
Subscribers	N/A	862 kb
Non-Subscriber	N/A

This report will only be available in electronic format, and AwwaRF will not produce a printed report. Download the report by clicking the pdf image above.

PRINCIPAL INVESTIGATOR:
Christopher Ziolkowski

OBJECTIVES:
The objective of this project was to develop prototypes of a direct burial device that does not require hard-wire contact to inject signal into a tracer wire. The device would eliminate the exposed end of the wire. The buried device was proposed to be located from above ground by means of a hand-held locator. The same locator could then be used to trace the wire. The buried device could receive enough energy to power the tracer wire and, optionally, return a unique code, providing identification.

BACKGROUND:
To help locate polyethylene (PE) pipe, water and gas utilities have traditionally placed tracer wires adjacent to PE pipes during installation. These tracer wires, when carrying an electrical signal, can generally be detected above ground. However, tracer-wire now requires exposing an end of the wire to inject an electrical tracer signal. This exposed end, and sometimes the entire wire, can be lost due to construction, homeowner activity, or corrosion, which inhibits or eliminates the ability to locate and trace the plastic pipe. The original concept was that the device would be placed at the end, or terminus of the tracer wire. The proposed name “terminator” was based on this idea. Tracer Wire Coupler (TWC) is in fact a better description of the device.

There is considerable existing technology for the location of buried Radio Frequency (RF) “tags” on utility assets. Gas Technology Institute (GTI) has expertise in adapting this technology for applications beyond simple location. This expertise drove the original proposal and the direction of the project work. Commercially available locators and components were used in the course of this project.

HIGHLIGHTS:
A successful prototype was developed and is in beta test with one gas utility. The prototype is a direct burial device that meets all of the proposal objectives. It is attached to the tracer wire prior to burial and provides good signal coupling to the tracer wire from an aboveground generator without requiring metallic contact with the generator. The system has been shown to be capable of locating several hundred feet of tracer wire on either side of the point of installation. There is a manufacturer interested in producing the buried portion of the tracer wire coupler. The locating equipment is available off the shelf from several sources. The utilities that have reviewed this project so far have expressed an interest in the Radio-Frequency Identification (RFID) functions built into the coupler.

APPROACH:
Locators from various manufacturers were evaluated by GTI. The project team sought the ability to both locate buried RFID devices and to perform pipe and cable tracing. All of these devices were at least demonstrated for GTI; several were retained for longer periods of testing. Units from two manufacturers were purchased by GTI and used in experiments to determine the feasibility of the technique.

After both the survey of existing equipment and some experimental work, it was determined that 8 kHz would be the signal frequency coupled into the wire. The 8 kHz frequency is supported by multiple manufacturers and is proven to provide adequate range. A separate antenna is also used purely for the location of the coupling device itself. This is the RF tag or ID antenna and has a frequency specific to the utility being located.

RESULTS/FINDINGS:
Samples of the TWC for gas distribution systems are currently in test with one gas utility with good results. Another gas company has accepted delivery of their samples and is evaluating the technology. Samples for water companies have been prepared and the companies contacted. One of the water companies has agreed to field test the samples when they are available.

Initial tests were carried out with a two-wire tracer TWC that was simply spliced into the line. After some testing and discussion, it was determined that a three-wire unit would be more useful. The third wire allows a sacrificial anode to be attached to the system to protect the tracer wire from corrosion. The three wire version has filtering built in that allows the anode current to pass but blocks the 8 kHz tracing signal from being lost through the anode.

IMPACT:
The prototype TWC fulfills several needs with respect to tracer wires. First, it couples the signal into the wire without need for direct metallic contact. Next, it is easily located and positively identified with off the shelf equipment. Lastly, it provides a means to attach sacrificial anodes without compromising signal quality. All of these combine to improve the longevity and ease of use of the tracer wire.

RESEARCH PARTNER:
Gas Technology Institute