New capabilities of ultrasonic inspection of metals

Abstract

The constantly increasing volumes of nondestructive inspection of objects and equipment having critical service lives requires an increase in inspection productivity and in the reliability of the most widely used methods, radiographic and manual ultrasonic. The advantages and disadvantages of these methods for inspection of weld joints, vessels, metal structures, etc. are widely known. Manual ultrasonic inspection done with use of general purpose instruments, both imported and domestic, has not only low productivity but also insufficient reliability [ 1]. The presence of a subjective factor in interpretation of the inspection results and the absence of an inspection record of the whole weld joint (current imported inspection instruments deriver printouts of tuning a~ echo pulses) also reduces the reliability of the method. In addition, current requirements for conducting inspections include taking into consideration corrections in sensitivity with a change in surface finish and waviness of the impeeted part on the side of which iuspeetion is conducted and also the temperature of the environment and the inspected part [2]. An increase in productivity and reliability of ultrasonic inspection of objects and equipment is possible with use of small units having a multiehannel inspection instrument and multielement acoustic systems and also with use of new methods of rapid diagn~ing. In connection with this the development and use of new equipment and methods simultaneously ~r~mg inspection productivity and reliability becomes increasingly pressing. The rapid development of electronics makes it possible to develop small right multiclmnnel inspection instnnnents and, together with use of multielement acoustic blocks to substa~tially increase the capabilities of ultrasonic inspection. "ALTES Ltd." Scientific and Technical Company has developed and is producing the small "SKARUCh" manual u~msonic inspection instrument combining the advantages of manual inspection (small and right equipment, high effectiveness) and automatic output of the document. The unit is designed for detection and determination of the characteristics of defects in weld joints (butt, T-, lap) and base metal of piping and metal structures with a wall thickness of 4-60 ram, The unit has an eight-el~nnel electronic block which is connected to the meehanoacousfic block through the information cable. The electronic block, equipped with an electroluminescent screen, operates either as a general purpose inspection instrument or thickness gauge, or as an automatic inspection unit. In automatic inspection a special meclmnoacoustic block, which consists of a mechanical device (one-sided MAB1 or two-sided MAB2), acoustic blocks with a system of frET) piezotrausducers built-in to them, and a sensor for measurement of the path covered (SP), is used. The MAB2 has an exteusible housing, which makes it possible to change the distance between the acoustic blocks (right and left) depending upon the thickness of the part and the width of the fdlet. The MAB2 is used for inspection of butt and lap weld joints by symmetric placement of the blocks on both sides of the weld joint and the MAB1 for inspection of weld joints with limited (one-sided) access, T- and comer joints, and'longitudinal butt joints of piping, and also for determining the remaining thickness and detection of separations in the base metal. The acoustic blocks have the capability of horizontal and vertical movement during movement of them along the weld joint and are equipped with exteusible stocks, which provide a stable position of the block on a working surface with curvature (such as in inspection of a butt joint of piping). The multielement acoustic block (AB) consists of 3-10 PETs (depending upon the inspected thickness) probing the whole cross section from one or two sides of the joint by different methods of ultrasonic inspection (combined, "duet," "tan