Abstract: Plural auxiliary carts 18 and 19 are connected to a measuring cart 11 in the width direction thereof which travels on a tank bottom plate 31 through universal joint mechanisms 26 and 27. Reflection type ultrasonic probes 22, 23 and coating film thickness gauges 24, 25 are provided with the respective auxiliary carts 18 and 19, and also a rotary encoder 32 which measures a traveling distance of the measuring cart 11 is attached to the measuring cart 11. Based on the outputs of the ultrasonic probes 22, 23, the outputs of the coating film thickness gauges 24, 25 and the outputs of the rotary encoder 32, the actual thickness of the tank bottom plate 31, that is obtained by subtracting the thickness of the coating film at a specific position of the tank bottom plate 31 measured by the rotary encoder, is measured and stored, and the thickness of every portion of the tank bottom plate 31 is displayed on a screen.

Abstract: A tube flaw detecting method detects a flaw portion in a heat exchanger tube constituting a boiler furnace wall using two probes, enabling one to carry out appropriate inspection work with a high efficiency. A transmitter probe and a receiver probe are juxtaposed in a circumferential direction, and an ultrasonic wave is transmitted from the transmitter probe to propagate. Repeated reflections occur at a tube inner surface and tube outer surface, and the wave is reflected at a crack extending in the circumferential direction to return, propagating likewise to be received by the receiver probe so that existence of the crack is confirmed. Thus, inspection work for a crack can be done with certainty with a simple arrangement.