With the development of ultrasonic wave signal analysis, it has become possible to measure the thickness of scale deposited on the inner surface of boiler generating tubes of thermal power stations and other facilities on the order of ±10?m. By this, it has become possible to readily grasp the scale thickness inside the entire furnace without extracting integrally sound pipes. The dissolving behavior of scale during the chemical cleaning of scale can be grasped in real-time and, by this, the remaining amount of scale after cleaning can also be readily understood.

(1) Measurement is possible even in narrow spaces with the use of an exclusive compact measuring device.
(2) Operation efficiency is good with the use of a battery drive. (AC power source is not needed.)
(3) Monitoring can be made even during cleaning. (Temperature inside the furnace of about 90°C.)