Corrosion monitoring is one of the most efficacious mechanisms that allow controlling the integrity of pipelines and its application is required by international standards in several situations. The ordinary technologies used in corrosion probes, like mass coupons, have some limitations regarding costs and QHSE issues; it leads to the development of alternative technologies. In the case of subsea pipelines, the use of the traditional coupons is limited to the " topside" section of the pipeline, usually in its beginning and end. It restrains strongly the process of integrity assurance in subsea pipelines. This paper describes the development of an ultrasound system of high sensibility to overcome these limitations. It is called "PROVUS" and it is able to estimate corrosion rates very accurately. This system presents many advantages when compared to the traditional coupons, such as: they are non-intrusive, easy to handle/deploy, safer and more flexible. This paper details the present stage of development of the ultrasonic corrosion probe, detailing: the validation process by means of over 6000 hours of "blind tests", i.e., tests in which the applied corrosion rate was only informed after its detection by the ultrasonic system; the applications for onshore and subsea pipelines; the mechanical design and the adjusts in course to turn the tool suitable for ROV (Remotely Operated Vehicle) operation.

1. Introduction

Corrosion monitoring is a very important mechanism to allow the evaluation of pipelines integrity.. Many standards require or recommend the use of corrosion probes as corrosion monitoring items. The use of the traditional coupons is not feasible for subsea pipelines except in the topside sections, i.e., normally in the pipeline's beginning and end.

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