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Methods of Overcoming the Effect of Attenuating Coatings on Pipelines and Risers on the Test Range of Long Range UT

Project Code: 0901-16

Objectives

To refine the technique identified in the exploratory work and to determine its operating parameters.

To demonstrate the performance attained experimentally, including the method of transmitting and receiving the signals.

To establish the increase in test range/sensitivity achievable.

Project Outline

The test range is reduced when the ultrasonic energy is lost from the pipe wall by absorption by the coating on the pipe or loss into the surrounding material, such as back-fill. The exploratory work showed that if these interactions can be controlled, their effect may be reduced, thereby increasing test range. A full study of the mechanisms of interaction of the ultrasonic guided waves with the surrounding material will be carried out to determine the optimum operating characteristics - test frequency, wave mode, pulse length and shape. This will be carried out using finite element modelling initially, followed by experiments on coated pipes, with a variety of different coatings, to demonstrate the performance achieved.

The anticipated requirements of this approach will mean that the usual methods of generation and reception of the ultrasonic signals will not necessarily be appropriate, and a study will be carried out of the best means of transmitting and receiving signals in order to implement this novel approach.

Relevant Industry Sectors

Oil, Gas, Petrochemical, Pipeline

Technical and Economic Benefits

There are many instances where pipes and pipelines cannot be easily examined non-destructively by other means, unless they are taken out of service. This is particularly true for lines which cannot be examined by an in-line inspection tool (pigging). Examples are: Cased road, rail and river crossings, sections of buried line where excavation is not possible and offshore risers. Current technology cannot always achieve a full examination of 100% of the length required on such sections, so that pipeline operators have to use other and more expensive technologies to complete the inspection task. Conventional inspection costs are in the region of $300,000 per km of pipeline. Long range inspections using guided ultrasonic waves may reduce this by at least 50%.

Longer test ranges allow full examination of buried pipelines with fewer excavations. In highly populated areas each excavation may cost as much as $30,000, so any reduction in the number of excavations represents a significant saving.

For more information please email:


contactus@twi.co.uk