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Title: On-line free span detection using the pipeline inertial pig
Category: Papers by Dr Andrew Palmer
Downloadable: Yes 
Project No.:
Research Agency:
Catalog No.: AP102
Date of Publication: 1992
Price: $25.00 US
Authors: A Evett, J Adams and A C Palmer
Abstract: The measurement of the structural geometry of a pipeline system and any deformation or mechanical damage present in the pipeline can be achieved in one pass by recently developed internal inspection tools. It has been found that the pipeline vibrational response of a pipeline measured by the tool has a direct relationship to the external supporting environment around the pipe. The results of this type of survey can be used as a basis for the determination of the length of a free span and its three dimensional geometry, the natural frequency of the span and the measurement of the amplitude of the vibration.

Based on this sensor information coupled with the other output data from the tool, fitness for purpose determinations can be undertaken. The basic geometric data can be enhanced by overlaying it with corrosion (wall thickness) data to provide a complete picture of pipewall profile and condition.

Recent experience with the GEOPIG tool has shown that the detection of unsupported pipeline sections is possible with a high degree of reliability. This is based upon the detection of the low-amplitude low-frequency transerse oscillations of the pipe section in unsupported pipe caused by the nteraction with the external water currents, and the forces introduced by the passage of the tool through the span. Vibrational responses have been detected and evaluated both on and offshore. NPSS is working in this field jointly with Andrew Palmer and Associates Limited.

Apart from its obvious application to pipeline free span detection, the tool has been used for more diverse applications related to commissioning, laying of rock dumps, mapping pipeline routes, and assessment of subsidence, scouring and upheaval, internal callipering and baseline surveying of pipelines. The presentation accompanying this paper describes the GEOPIG tool, together with software systems for reporting tool runs.

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