April 2009 Vol. 64 No. 4
Business
Tech Upgrade Enhances Utility’s Locating Program
Massachusetts is rich in history. While some historical buildings still stand as new, architecture pops up around cities and not everything “old” is charming. An example is the aging infrastructure that exists in many cities throughout the state and is often hidden or buried, making it difficult to locate.
Unitil Corp., a public utility holding company that provides gas and electric utility distribution, faces this problem daily. Some of the company’s infrastructure is over 100-years old and can be difficult to locate because the pipe joints, which are held together with a mechanical coupling, may no longer be conductive as they have shifted since being buried.
The difficult challenge of locating these lines belongs to David Joyce, energy production and corrosion supervisor at Unitil. In central Massachusetts, about 30 miles north of Worcester, Joyce manages the annual survey of Unitil’s 21 rectifier systems, which entails locating as much as 600 miles of piping. The purpose of the annual survey is to ensure that Unitil is compliant with state codes regarding corrosion.
“Rather than being joined by a mechanical coupling, pipes today are welded together, allowing the joints to be easily located,” said Joyce. “Now, when I have to locate our rectifier systems and find a mechanical coupling that has shifted, I bond over the coupling with wire, so that it can be locatable for the next time we have to perform the annual survey.”
Joyce typically uses a high-frequency locator with a 480 kHz frequency to find the couplings on the aged utility infrastructure. However, at this frequency, it was difficult for Joyce and his crew to locate the Unitil lines.
When Joyce’s high frequency locator lost its signal, it meant that a coupler had been located due to shifting, disrupting the cathodic protection system’s AC/DC current. Joyce’s problem with locating occurred when the couplers hadn’t shifted. In this case, the high frequency locator caused the signal to bleed into and around the coupler, preventing Joyce from knowing where the coupler was located.
Change in direction
In 2008, Joyce attended a class on utility locating at Staking University in Manteno, IL, where he learned about the RIDGID SeekTech SR-60 utility locator.
With the SR-60, users can locate at the broad frequency range of 10 Hz to 490 kHz, and can tune the frequency 1 Hz at a time, allowing the SR-60 to be used with any pre-set frequency transmitter. The unique passive search mode can be used to search all broadband passive frequencies at once, allowing for easy identification of unknown metallic lines in the target area. These features have allowed Joyce to gain a much more comprehensive and accurate understanding of the Unitil underground infrastructure.
“I’ve programmed my unit to 120 Hz and now the signal doesn’t bounce off the coupler. The frequency that the cathodic protection rectifiers output is 120 Hz; by following the line with the RIDGID SR-60 set at 120 Hz, we are able to tell where the signal drops off — indicating that we have an open coupling. We’ve been able to accurately locate the dressler couplings, and as a result save time and money,” Joyce said. “The SR-60’s display screen also helps streamline the locating process because all the information I need is on one, easy-to-read screen. I like seeing the peak and null and continuous running depth all on one screen. I don’t have to push multiple buttons to change screens for the information that I need. It’s all in front of me, all the time.
“Locating the couplers is a long, labor-intensive process, and before we starting using the newer equipment, we randomly pot holed to verify utility lines. Now, I can narrow in on the couplers and dig only one hole, rather than multiple holes, to verify a utility line,” added Joyce.
The SR-60’s accuracy also has reduced the need for a vacuum truck to pot hole. When Unitil used the high-frequency locator, a vacuum truck was needed for three to five days, so that it could dig up multiple points.
“We’re now saving a fortune because we don’t need the vacuum truck as long because the locate marks are accurate, and therefore we don’t have to dig a lot of holes. We also don’t need the crew on the job as long because we’re more efficient since we know exactly where we need to dig,” Joyce added, “It used to take all day to locate a joint, and now with the SR-60, it only takes half an hour to locate per coupling.”
The RIDGID SeekTech ST-33Q transmitter also helped Joyce reduce time on the jobsite. The ST-33Q transmitter induces a stronger signal onto a utility line at a lower frequency, and when used in induction mode, it induces at 8 kHz and 33 kHz.
“I like using the ST-33Q because it allows me to locate long distances without having to reposition the transmitter every so many feet. At one point it allowed me to locate a pipe that went almost one mile,” said Joyce.
FOR MORE INFORMATION:
Ridgid, (800) 769-7743, www.ridgid.com
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