Structure Design And Motion Performance Study Of Mobile Device For Automatic Testing Of Welds In Heat Exchanger

The tube-tubesheet fillet weld is the important connection structure of the heat exchanger.And its quality directly affects the operation status of heat exchanger.It is the key to ensure the long-term normal operation of the equipment and no leakage.The fillet weld needs to be detected and maintained regularly.At present,the testing of fillet weld in tube-tubesheet is generally operated by professionals.However,the efficiency of manual testing is low,the missed testing sometimes occurs and the quality of testing is difficult to control.Therefore,it is necessary to design a set of tube-tubesheet fillet weld automatic testing mobile device.A design scheme of crawling robot which can carry nondestructive testing equipment was presented.The main research is crawling foot which is the key force element of crawling robot.And its structure was designed.The load stability of crawling robot was studied deeply.The main works is as follows:(1)The structure of crawling robot was designed by analyzing the characteristics of the heat exchanger.The crawling robot and testing equipment weight 25kg.The load capacity of crawling foot was simulated in both vertical and horizontal heat exchanger by ANSYS.The simulation results showed that when a single crawling foot worked on the vertical heat exchanger,it could maintain stability with a load of 25kg in the inflating condition and its maximum sliding distance was 0.0098mm.Its maximum load was 15kg in the self-locking condition and its maximum sliding distance was 0.0078mm.When the load reached 12kg,the crawling foot slipped and its maximum tilting displacement was 4.03mm.As a result,the robot couldn't complete the testing task.(2)A improved scheme of new crawling foot with three heel was proposed by analyzing the cause of slipping.The new crawling foot can grasp three tubes which improves its reliability.The structure of improved crawling foot was designed theoretically.(3)The load capacity of improved crawling foot was simulated.The simulation results showed that the maximum load in the inflating condition was 52kg its maximum tilting displacement was 0.36mm.The maximum load in the self-locking condition was 20kg and its maximum tilting displacement was 01.8mm.Both conditions could meet the stability requirements.Two virtual prototypes of crawling robot were established according to the working characteristics of the heat exchanger.And dynamic simulation was performed to verify that the two robots could still maintain good stability during the movement.(4)The vertical heat exchanger experimental prototype system was developed.The experimental platform was set up and the loading experiment of crawling foot was carried out.The result showed that the maximum load of inflating condition was 38kg and of self-locking condition was 15kg.The crawling robot carried out a motion experiment such as rotation and linear motion which verified the robot had good stability.