The shell thicknesses following a breakout have been accurately measured using a laser scanner. The variations inshell thickness were related to mould thermal monitoring data.The highly detailed 3D thickness scans confirm that local variations in shell thickness may occur in the mould. Incombination with mould thermal monitoring, the root cause of these thickness variations was identified.In this paper, the breakout shells from two incidents at the high speed thin slab caster at the Direct Sheet Plant(DSP) are discussed. The first breakout was related to entrapment of a large inclusion on the wide face. Thesecond was a narrow face breakout related to localised shell thinning and incorrect taper settings.In both cases, the breakouts were associated with local reductions in shell thickness. Temperatures at thecorresponding locations in the mould were lower, indicating an ‘air’ gap or an insulating layer between the steelshell and copper mould. Calculations using CON1D verified the existence of an insulating layer and gave a betterunderstanding of the events that led to these breakouts.
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