Harco Corporation

Marvin L Miller

Clark P Weldon

Stephen L Wolfson

Frank E Rizzo

In the present invention a method and apparatus for electrical surveys of offshore metal structures includes measuring the electrical potential difference between the structure and an electrolyte, such as sea water and/or the sea bottom, in which the structure is contained. Such measurements are made at roughly approximated recorded distance locations along the structure and the approximate distance information is corrected based on periodically taken accurate distance measurements. Provision is also made to correct data for line currents in the structure, and a method is disclosed for examining the effectiveness of an electrically insulating member connected in the structure. Moreover, an improved insulated wire having minimum insulation holidays and a method for making the same are disclosed.

Method and apparatus for electrical surveys of offshore metal structures

A method and apparatus for conducting offshore pipeline electrical surveys is characterized by initially locating and marking the pipeline, traversing the length of the pipeline towing a reference electrode in close proximity to the structure, providing a supply of wire having one end electrically and mechanically connected to the pipeline at a reference location, playing out the wire along the length of the pipeline through a distance measuring device while transporting the supply of wire and towing the reference electrode, and measuring and recording the potential difference between the reference electrode and pipe either continuously or at spaced test locations along the length of the structure. The method and apparatus are further characterized by alternately connecting and disconnecting an electrical power source to the pipeline at the reference location, measuring and recording the potential difference in both connected and disconnected modes at the test locations, and measuring and recording the depolarization and/or polarization times when the power source is disconnected and/or connected, respectively, to the pipeline.

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Houston, TX, United States of America

Marvin L Miller