TEST NDT International trains US bridge inspectors in phased array inspection techniques
09/11/2007
TEST NDT International recently conducted ultrasonic phased array training for the DOT (Department Of Transport) in Nevada. The inspection of bridges in the USA has been closely scrutinised recently following the collapse of the I35W bridge over the Mississippi river in Minneapolis earlier in the year. The inspection of bridges is a state responsibility, not a federal responsibility, and each state has its own department of transport with responsibilities for developing and administering their own bridge inspection programme.TEST NDT was asked to provide the training based on its reputation as a leader in the phased array training and consulting field. The training was based around the OmniScan MX phased array system.
During the training, help was given in the development of inspection procedures and in addition to the usual classroom based theory and practical exercises, a field trip was conducted to perform the inspections on an in-service bridge.
The main area of concern is on the link pins, which are 22 inch (559 mm) long, 4 inch (101.6 mm) diameter forged pins. The bridge inspected was almost 80 years old and had been relocated once already from its original site to another river crossing. The bridge had to be totally dismantled and shipped to the new site for re-construction.
A shallow-angle swept sectorial scan technique was developed using a sample of representative material with several side-drilled holes at different depths from the probing surface to facilitate a TCG (Time Corrected Gain) technique throughout the length of the pin. No defects were found in the pins inspected. The inspection will now be performed on the other bridges throughout the state.
For further details of this technique, or phased array training/consulting, contact TEST NDT International on 01772 616913 or e-mail: ndtguru@aol.com
