Pipeline Freespan Monitoring

Abstract

A technique has been developed for acquiring and analysing the vibration signature of pipeline freespans. The information derived can provide a cost effective means of avoiding unnecessary free span rectification work.

When assessing pipeline freespans, two aspects require to be considered separately. First, the stresses occurring in the span as a result of its own weight and current drag require to be estimated. Second, the susceptibility of the span to vortex induced vibration requires to be considered. In the absence of any quantitative measurements, span assessment requires to be made on the basis of conservative assumptions regarding such unknowns as span length, end fixity, axial tension etc.

Careful analysis of the vibration signature gives a quantitative measurement relating to each of the above, in addition to allowing more direct assessment of the vulnerability of the span to vortex shedding.

Experience has shown that the application for this system can dramatically reduce the rectification work required.