A new method for measuring the wall thickness of welded steel tubes

　　This device consists of a measuring head of laser ultrasonic measuring equipment, a motivating laser, an irradiating laser and a convergence optical element that is used to collect lights reflected from the surface of the pipe to the measuring head. The important mass parameter for pipe production is wall thickness. So it is needed to measure and monitor its parameter in the course of pipe production. You should create a laser ultrasonic survey to measure the wall thickness of the welded steel pipe .It is a measurement method which is based on pulse echo principle to ensure the wall thickness through measuring the spreading time of ultrasonic pulse.

　　This device uses a motivating laser that will lead ultrasonic pulse into the surface of the pipe. And then this ultrasonic pulse spreads into the pipe and reflects on the inner wall. And we could measure the signal that return to the outer wall through putting an irradiating laser aiming to the surface of the pipe. This reflected signal will be sent into an interferometer where there is a homocentric interferometer. A analysis and process device makes sure the time difference between input ultrasonic signals and reflected ultrasonic signals to figure out the wall thickness value under the circumstances of having known the spreading speed in the pipe.

　　In order to make this device measure the wall thickness of welded steel pipe accurately and stably, it is necessary to make laser ultrasonic measurement device work under the best working condition. And its prerequisite is that the light beam sent out by motivating laser and the light beam sent out from the irradiating laser must meet on the assigned place. However, first of all, we must try our best to keep accurately the distance between measuring pipe and measuring head. In addition, practices have proved that it is hard to ensure the best working condition under above environment situation, especially in the process of rolling, impossible to adjust the laser ultrasonic measurement device. And this can only be made through the regular control of the device. Otherwise, the distance between measuring head and the surface of the pipe of the laser ultrasonic measurement device must be kept in an ideal index value to make sure the reflected laser light from the surface of the pipe could best input the measurement device.

　　Set at least two light resources that send the same one bundling light and are fixed on the different places of the measurement head. And at least two light resources can be foxed on the measuring head like this and be corrected direction. Namely when there is a beforehand distance of pipe and measuring head, the bundling lights from these two light resources will cross on the surface of the welded steel pipe. No matter how long the distance between the head and the surface, you can easily measure with the method above. Thus, it can be sure that the laser ultrasonic measurement device has best working condition under the rough rolling condition, enhancing the productivity as well as quality of the welded steel pipe.