Water-jet Ultrasonic Focused Testing Technology For Lip Welding Of Nuclear Manual Globe Valve

With the rapid development of the domestic nuclear industry,it is more and more important to ensure the safety of nuclear.Nuclear manual globe valve is widely used in various loop systems of nuclear plants due to its unique performance advantages such as good sealing,small working stroke and short opening and closing time.However,due to the complex valve manufacturing process and harsh service environment,the thickness of the surfacing layer of the lip weld girth weld is too thin,resulting in insufficient overall strength of the valve,which may lead to leakage accidents under the long-term action of internal pressure,which will seriously affect the safety of nuclear station.Therefore,regularly non-destructive testing of internal defects and weld thickness of lip welds is an important means to ensure valve sealing.At present,the domestic scholars’ research on the lip welding seam of nuclear valves mainly focuses on the valve manufacturing process and the improvement of welding technology,There are few related researches on nondestructive testing of lip welds in nuclear valves.In this study,in view of the ultrasonic testing difficulties such as the raised surface,rough surface,thin surfacing layer and small internal defect size of the residual height surface of the nuclear valve sealing lip welding ring weld,the water-jet ultrasonic focusing testing technology for the nuclear manual globe valve lip welding seam was proposed.The specific research content of the paper is as follows:First of all,in view of the complex structure of the testing object and many difficulties in testing,the testing method is studied.Based on the principle of water immersion focusing testing,through mathematical model derivation,the relative position of the focal probe in of the ultrasonic wave in the plane girth weld and the curved girth weld are studied under the same water distance.Second,numerical simulation technology is used to study the influence of the focal probe position and focal probe size under the same water distance,and the variation law of the focal probe position and focal probe size with the curvature of the girth weld is analyzed;Third,by changing the testing water distance,the focus position of the ultrasonic waves in the girth welds with different curvatures is consistent,and the related expressions of the diameter of the curved surface,the water distance and the size of the focal probe are obtained.Fourth,build a water immersion focusing testing system to test the internal defects of the lip welding simulation sample with reference to the simulated water distance;Fifth,in view of the nuclear on-site testing environment and work requirements,the water immersion method cannot be used for testing.Therefore,a water-jet focusing testing method is proposed,the corresponding testing tooling is designed,and a water-jet focusing system and water circulation system for nuclear onsite testing is built;Finally,the testing of the lip welding seam of nuclear valves was carried out,and the thickness of the welding seam was measured by the water-jet focusing testing method,and then the metallographic anatomical analysis of the valve was carried out.The effective speed of sound propagating in the weld area is analyzed,and the influence of changing the incident point and incident angle on the amplitude and arrival time of the characteristic signal is analyzed,and the shape of the defect inside the weld is judged.The research results showed that compared with the plane testing object,although the focal depth of the focusing probe in the workpiece and the size of the focal probe formed are increased due to the adverse effect of the girth weld excess surface being a curved surface,it still remains in the workpiece.Effective focusing is formed inside the weld,and the focused sound field can accurately cover defects of different depths by correcting the detection water distance.The water-jet ultrasonic focusing testing technology can effectively solve the problem of acoustic coupling caused by the complex surface of the workpiece.The focused sound field formed by the focusing probe has the advantages of concentrated sound beam and high energy,which can be applied to the testing of small-sized defects inside the lip welding.The designed testing tooling,It can be adapted to the testing environment of the nuclear site and realized semi-automatic testing.In the study of lip welding thickness measurement,the waterjet focused ultrasonic testing technology can receive relatively high-quality defect reflection signals,Compared with the metallographic results,the sound velocity of ultrasonic waves in the lip welding seam area is 5150 m/s.After the sound velocity is corrected,the maximum difference between the ultrasonic testing value and the metallographic measurement value is 0.06 mm,and the minimum difference is only0.02 mm,which meets the testing requirements of the nuclear.The water-jet ultrasonic focused testing technology proposed in this study can effectively test the internal defects and weld thickness of the lip welds of nuclear valves.It has important engineering practical significance for preventing seal failure,avoiding the leakage of radioactive substances,and ensuring the safe operation of nuclear station.