Laser ultrasonic furnace tube coke monitor. Quarterly technical progress report. Report No. 5 for reporting period May 1, 1999 through August 1, 1999

The overall aim of the project is to demonstrate the performance and practical use of a probe for measuring the thickness of coke deposits located within the high-temperature tubes of a thermal cracking furnace. The objective of work during this period was to enhance the sensitivity and signal-to-noise ratio of the probe measurement. Testing identified that the primary source of signal noise was traced to imperfections in the sacrificial stand-off, which was formed using a casting procedure. Laminations, voids, and impurities contained in the casting result in attenuation and dispersion of the ultrasonic signal. This report describes the work performed to optimize the signal conductance of the sacrificial stand-off