The present paper describes a summary of experimental work. Carried out at Heriot-Watt University, in support of a new philosophy, proposed and developed by R.S.T. Projects Ltd, whereby low cost instrumentation is installed inside a conventional bi-directional or foam pig. Two methods have been investigated. The first, more speculative, technique investigates how the pipeline acoustic response to an "active" sound source is affected by the nature of an internal wax coating. Preliminary results from "static" acoustic tests are presented which indicate that differences in wax coating (type and thickness) can be detected. Further extensive investigation is required to adapt this for a moving pig and develop the appropriate signal processing techniques. This method may constitute an effective means of d~ermining the degree to which a line is coated with soft wax as the absorption characteristics are particularly effective in changing the acoustic response of the pig. The second technique used an on-board accelerometer to measure the vibration signal of the pig. The results indicate that 1be intensity and acceleration fi'equency spectrum of the signal may be related to the internal coating of the line. The condition of the pig disks may also be inferred.
The internal inspection of pipelines has come to rely on a sophisticated level of instrumentation. So called "intelligent" pigs are capable, under the best of conditions, of identifying problems relating to cracking, pitting, corrosion and pipeline geometry- see Cordell (1999) for a general discussion. In the majority of cases the pigs have been specifically designed to perform the particular inspection. Examples of the application of such tools may be found in the papers by Crouch et al (1996) (magnetic flux leakage and ultrasonic), Willems and Barbian (1995)(ultrasonic) and Wade and Adams (1995) (Geometry).
