Cement kilns need to have their lining condition regularly checked in order to ensure their flawless operation. Measurement of the lining thickness is carried out during maintenance down-times. Performing lining thickness measurement with StratoTest C considerably reduces these down-times as instead of the traditional measuring method of drilling numerous inspection holes, only one drill hole is required for calibration of the gauge. From there on, the measurement is carried out non-invasively and hence significantly saves working time as well as maintenance costs.