Thickness measurement system for bottom floor of cylindrical tank

Plural small carriages 18, 19 arranged laterally are connected a carriage 11 for measuring via universal joints 26, 27 respectively, the carriage 11 running on the bottom plate 31 of the tank. Reflection-type ultrasonic probes 22, 23 and thickness measuring devices 24, 25 for paint film are disposed on the respective small carriages 18, 19 and a rotary encoder 32 for measuring travel distance is disposed on the carriage 11. Based on the output of the ultrasonic probes 22, 23, the thickness measuring devices 24, 25, and the rotary encoder 32, real thickness of the bottom plate 31 subtracting the thickness of the paint film thereof at the specific position measured with the encoder 32 can be measured. The results of the measured thicknesses are memorized as data and the thicknesses of the respective portions of the bottom plate 31 are shown in a display.