The erosive wear of fibrous aluminosilicate insulating materials has been studied to establish the mechanisms of damage and to obtain quantitative measurements of erosion rate for use in plant design. The effects of erosive particle size, particle velocity and impact angle on wear rate have been examined in experiments with a gas-blast erosion rig and silica sand particles. For these extremely weak and porous materials, conventional techniques based on weighing cannot be used to quantify erosion damage. A non-contact optical method has therefore been developed. The erosion rate exhibited a power-law dependence on velocity and a linear dependence on impact angle, with a maximum at 90 o . An empirical equation was established to predict erosion rate as a function of impact angle (between 20 and 90 o ) and particle velocity (between 6.7 and 12 m s - 1 ), which can be combined with fluid mechanical models for particle motion to model the wear rates of fibrous insulation in high temperature industrial plant.