th Middle East Nondestructive Testing Conference , 7-10 October 2012 , Kingdom of Bahrain Phased Array Ultrasonic Testing of Welded Joints in Plastic ( PE ) Pipes
A reliable Non-Destructive Testing approach is required for the inspection of polyethylene (PE) butt fusion joints in various material grades and pipe sizes. The nature of butt fusion joints is that the fusion zone is relatively small and the inspection solutions are often restricted by the existence of an external weld bead. This weld bead restricts the probe placement and the probe needs to be positioned in a non-optimal position for the weld inspection. The PE material grades have low velocity and high frequency dependent attenuation, which will complicate the inspection of thicker pipes. In this paper, phased array ultrasonic techniques are presented and their capabilities are evaluated. The techniques utilise customised water wedges to be able to generate forward angle beams to cover the weld within the PE pipe. Techniques have been developed for pipes with outer diameters between 220-710mm and thicknesses between 14-45mm. Probe and wedge parameters have been optimised for this range of pipes. The capability of detecting circular defects with diameters between 1.5-8mm on pipes with an outer diameter between 220-710mm using a phased array ultrasonic inspection solution, and the challenges overcome when working with this type of material, are presented.
High-Density Polyethylene Piping Butt-Fusion Joint Examination Using Ultrasonic Phased Array
With the increasing use of high-density polyethylene (HDPE) piping for nuclear applications, nondestructive evaluation is an important tool for evaluation of the integrity in fused joints. This paper will discuss the method of using ultrasonic phased array for inspecting butt-fusion (BF) joints in HDPE piping. The benefit of phased array is the ability to perform a volumetric inspection using multiple angles, which greatly increases the probability of detection of defects and allows the data to be analyzed using a representative two-dimensional image of the joint. It has been determined that successfully producing BF joints is highly dependent on environmental and mating-surface conditions. The primary defects of concern are lack-of-fusion, an area of the joint where there is no bond, cold fusion, an area of partial bond, and inclusion. Phased array has successfully demonstrated the ability of detecting and characterizing these defects using low frequency ultrasound. Factors addressed include joint location, wall thickness, material temperature, transducer wedge material, and manual versus automated data acquisition.
Modelling of the butt fusion welding process
Abstract The bead up stage of the butt fusion welding of plastic pipes is modelled by treating the melt layer as a squeeze film containing between two parallel annular rings to which fluid is supplied by the melting of the pipe ends. The lubrication approximation is used to simplify the solution of the governing equations with the melt treated as a non-isothermal power law fulid. Predicted melt layer thicknesses agree well with experimental data over a wide range of operating conditions. Also, this model is used to determine flow characteristics such as the radius of flow separation and the place of zero shear stress in the melt layer, both of which influence the microstructure of the joint.