Non-invasive, high resolution detection of electrical currents and electrochemical impedances at spaced localities along a pipeline

US5087873A · kind A · utility

Assignees

• New York Gas Group · US
• Southern California Gas Company · US
• Columbia Gas System Service Corporation · US

Inventors

• John C. Murphy · Clarksville, US
• Glenn S. Hartong · Columbia, US
• Ralph F. Cohn · Brookline, US
• Patrick J. Moran · Arnold, US

Key dates

• Filing date: Apr 24, 1991
• Grant date: Feb 11, 1992
• Expiry date: Apr 24, 2011

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N17/02
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Electrical current distribution in the soil surrounding a buried pipeline is detected by applying an AC electrical potential between the pipe and a buried electrode spaced from the pipe. The magnetic field at spaced localities along the pipe arising from currents transverse to the pipe is detected. Additionally, a potential containing a plurality of alternating frequencies is similarly applied to the pipe and the magnetic field induced by the resulting electrical current both along the pipe and transversely of the pipe is detected. The magnetic field is detected by correlation discrimination at spaced locations along the pipe and across the spectrum of the impressed frequencies. The detected data is used to determine the capacitance and resistance of the soil/pipe interface at localities along the pipe and to generate impedance plots which indicate characteristics of that interface.