Oil Transmission Pipelines Condition Monitoring Using Wavelet Analysis And Ultrasonic Techniques
by Dr. Waheed Abushanab
Proper and sensitive monitoring capability to determine the condition of pipelines condition is desirable to predict leakage and other failure modes, such as flaws and cracks. Currently used methods for detecting pipeline damage rely on visual inspection or localized measurements and thus, can only be used for the detection of damage that is on or near the surface of the structure.
This thesis aims at developing reliable, inexpensive and non-destructive technique, based on ultrasonic measurements, to detect faults within Carbon steel pipes and to evaluate the severity of these faults. The proposed technique allows inspections in areas where conventionally used inspection techniques are costly and/or difficult to apply. This work started by developing 3-D Finite Elements Modelling (FEM to describe the dynamic behaviour of ultrasonic wave propagations into the pipe’s structure and to identify the resonance modes. Consequently, the effects of quantified seeded faults, a 1-mm diameter hole of different depths in the pipe wall, on these resonance modes were examined using the developed model.
An experimental test rig was designed and implemented for verifying the outcomes of the finite element model. Conventional analysis techniques were applied to detect and evaluate the severity of those quantified faults. However, those signal processing methods were found ineffective for such analysis. Therefore, a more capable signal processing technique, using continuous wavelet techniques (CWT), was developed.
The energy contents of certain frequency bands of the CWT were found to be in good agreement with the model predicted responses and show important information on pipe’s defects. The reported technique proofs to be reliable and sensitive for such minor pipe structural related deficiencies and offers a reliable and inexpensive tool for pipelines integrity management programs.