Abstract: Offshore or onshore electrical surveys of buried or submerged structures such as pipeline are conducted in a fixed-cell-to-moving-cell fashion either before or after one or more established pipe-to-electrolyte potentials can be obtained. The results of the fixed-cell-to-moving-cell survey are then corrected by a summation of the fixed-to-moving-cell recorded potential and the established potential at the location of the established potential to obtain a reliable electrical survey of the structure. As indicated, the fixed-cell-to-moving-cell survey may be conducted either before or after the established potential is obtained or either before or after a disposable wire survey using a direct connection to the structure.

Abstract: An electrical survey of buried structures such as underwater or underground pipelines utilizes the steps of connecting one end of an economically disposable wire from a wire supply to the structure, either directly or through a heavier lead, the opposite end being electrically connected to a cell. The cell is moved along the structure together with a wire supply and a meter to obtain periodic measured structure-to-electrolyte potential values. If the wire is accidentally or intentionally disconnected during the survey, a stationary electrode is positioned at the wire break or last valid measured reading, such electrode being reconnected to the free end of the wire from the supply. The survey then continues periodically obtaining electrode-to-cell potential values. A structure-to-electrolyte potential profile is obtained by summing the last valid recorded structure-to-electrolyte potential value with each electrode-to-cell values. The summing may be done after the survey is completed by computer.

Abstract: 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.