Methods and apparatus for measuring the thickness of a deposit of material on an internal wall of a structure, and to determine the stiffness of a material deposited on an internal wall of a estrtutra

摘要

A method of measuring the thickness of any deposit of material (28) on an inner wall (12) of a structure (14). The method comprises: (a) causing vibrations in the structure; (b) detecting said vibrations in the structure; (c) determining a resonance frequency of the structure based on the detected vibrations; and (d) determining the thickness of any deposit of material on the inner wall of the structure based on the determined resonance frequency.