Strategic Objectives

  1. To develop novel ultrasonic inspection techniques and procedures for the examination of polyethylene tank materials of various sizes (thickness and diameter) and joint configurations to a defect detection level that will enable operators to safeguard against the failure of these tanks in service and allow them to be introduced into new and more demanding applications.
  2. To develop high power angled compression wave probes (generated from Phased Array or Fixed Element transducers) that are far less easily attenuated than the more commonly used angled shear waves in terms of ultrasonic beam configuration, frequency spectrum, damping characteristics for the required pulse width, signal to noise ratio and, for the case of phased array probes, generation of appropriate ‘delay law(s)’ to attain the correct beam angle(s) and sweep and focal length(s).
  3. To develop defect acceptance criteria through a series of accelerated creep rupture tests to ascertain the critical defect size for the specified service life of the tank. The derived defect acceptance criteria to cover the target range of defects and joint configurations will be evaluated for defect detection capability using the ultrasonic NDE technique parameters developed as part of the project.
  4. To create a database of critical defect sizes that cause a reduction in the long-term integrity of each type of welded joint.
  5. To design and build an ultrasonic inspection system and sensors/transducers for the reliable volumetric examination of thermoplastic tank, and tank/nozzle, joints during installation and in-service. Currently there are no commercially-available ultrasonic probes for the inspection of thick-section thermoplastic welds and specifically phased array, fixed array and Time of Flight Diffraction (TOFD) probes with low frequency and high power that are required to overcome the high attenuation effects on the ultrasonic beam.