Tech Upgrade Enhances Utility’s Locating Program

April 2009 Vol. 64 No. 4

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.