An array-based system for monitoring cracks in industrial plant at high temperatures

We have designed ultrasonic arrays to monitor fatigue cracks in steel components of industrial plant operating at temperatures up to 400°C, and developed an imaging algorithm to process the data. The crack monitoring system uses two monolithic arrays based on lithium niobate, a piezoelectric material which works at high temperatures. The transmitting array fires a steered beam and diffracted signals from flaws in the test subject are collected on individual elements of the receiver. Real fatigue cracks have been imaged at room temperature and the tips located to within 0.5 mm of their known positions. Side-drilled holes simulating flaws have been successfully identified from data collected at high temperatures.