Non-destructive testing (NDT) and inspection of the blast furnace refractory lining by stress wave propagation technique

Abstract

Generally speaking, a blast furnace is the main equipment in Ironmaking and the campaign life of a blast furnace depends on its remaining hearth refractory lining [1]. The Acousto Ultrasonic- Echo (AU-E) is a stress wave propagation technique that uses time and frequency data analysis to determine coarse-grained material thicknesses, such as refractory and stave materials in operating blast furnaces. A mechanical impact on the surface of the structure (via a hammer or a mechanical impactor) generates a stress pulse, propagating into the furnace layers. The wave is partially reflected by the change in refractory layer properties, but the main pulse propagates through the solid refractory layers until its energy dissipates. The signal is mainly reflected by the refractory/ molten metal interface, or alternatively by the build up/air or molten metal interfaces that are formed between internal layers or at external boundaries. In this paper, we describe the AU-E technique in details and demonstrate a few results that are indicative of the technique reliability and accuracy.