Specific Application NDE Method Leads to Development of Novel Microwave NDE Technique

Several years ago, a need was identified to develop an improved nondestructive inspection method to volumetrically inspect dielectric materials. Specifically, an inspection method for detecting defects in rubber expansion joints was needed to assist in preventing leaks in large electric power plant steam condensers. In response to this demand, a microwave based inspection technique was developed and patented by Evisive, Inc. Once the technique was developed and tested, it was found to be a powerful NDE technique that had uses for many dielectric materials. The technique can also be successfully used on composite materials containing conductive components but whose construction makes them overall nonconductors or bulk dielectrics, for example, carbon fiber composites.

Expansion Joint Inspection

Most steam-cycle electric power plants employ rubber expansion joints between the condenser and the turbine. The expansion joints have multiple composite layers. Typical dimensions for such an expansion joint are in the neighborhood of 40 meters (131') circumference, by 25 cm (9.8") wide, by 1 cm (0.4") thick. Under normal operating conditions, there is a vacuum on the inside of the joint, and 1 atm pressure on the outside. Thus when such a joint fails, it is prone to fail catastrophically.