Harco Corporation

Northwest Pipeline Corporation

Frank E Rizzo

Clark P Weldon

Marvin L Miller

David C Katz

Leslie G Colter, Jr

A method and system for detecting and preventing Stress Corrosion Cracking (SCC) in buried pipelines or other structures is presented. The basic principle of the invention is to use a plurality of test coupons which are placed in the same environment as a pipeline or other structure of interest as indicators of the development of SCC in the structure of interest. Loading and temperature of the test coupons are controlled. The test coupons are given a range of different Cathodic Protection (CP) levels, with the range of CP levels selected so as to encompass the CP level at which SCC would be expected to occur. The occurrence of cracking in a test coupon indicates levels of CP which will sustain SCC. SCC is prevented in the structure by application of a level of CP which did not sustain SCC.

Method and system for detection and prevention of stress corrosion

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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Spring, TX, United States of America

Frank E Rizzo