Patrick Moran

US Patent:

51266547, Jun 30, 1992

Filed:

Apr 2, 1990

Appl. No.:

7/504100

Inventors:

John C. Murphy - Columbia MD
Glenn S. Hartong - Columbia MD
Ralph F. Cohn - Worcester MA
Patrick J. Moran - Arnold MD

Assignee:

New York Gas Group - New York NY
Southern California Gas Company, - Elmonte CA
Columbia Gas System Service Corporation - Columbus OH

International Classification:

G01N 2726

US Classification:

324 712

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.

US Patent:

50878735, Feb 11, 1992

Filed:

Apr 24, 1991

Appl. No.:

7/690290

Inventors:

John C. Murphy - Columbia MD
Glenn S. Hartong - Columbia MD
Ralph F. Cohn - Worcester MA
Patrick J. Moran - Arnold MD

Assignee:

New York Gas Group - New York NY
Southern California Gas Company - Elmonte CA
Columbia Gas System Service Corporation - Columbus OH

International Classification:

G01N 2726
C23F 1302

US Classification:

324 712

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.