High Temperature Strain Measurement Of Teepipeline

In pressure piping systems,tee is a common component and widely used in in the fields of petrochemical,chemical,nuclear and aerospace.Tee pipeline is much more dangerous than the rest of the piping system due to the discontinuity of its structure and the irregular flow of fluid in the pipe at the pipeline junction.The medium in chemical equipment has the characteristics of high temperature,high pressure and inflammable and explosive.Once the leakage occurs,the loss will be immeasurable.Therefore,it is very important and necessary to monitor the stress and strain of the tee-pipe and understand the rule stress and strain`s change with tee pipe`s working condition.There are several methods for high temperature strain measurement of tee pipelines,such as laser interferometric sensor measurement,fiber grating sensor measurement,and so on.However,from the measurement accuracy,ease of use and cost,and other aspects of the measurement,the high temperature resistance strain gauge measurement technique is adopted to measure the high temperature strain of tee-pipe.Based on strain electrical measurement principle,the high temperature strain contact measurement method has the advantages of high reliability and good adaptability,and has been the main way of high temperature strain measurement.In this paper,KYOWA KH-5-350-G4-16D5M3 high temperature strain gauge and TST3826 F strain gauge and static strain test system are used to measure the high temperature strain of tee-pipe that the main pipe`s outer diameter is 133 mm and the branch pipe`s outer diameter is 68 mm.The KYOWA GW-3C-M9 spot welder is used to spot weld the high temperature strain gauge on the surface of the cylinder to make the measurement result more accurate;The three-wire connection method was used to eliminate the influence of the wire resistance on the measurement results.The high temperature strain gauge was arranged by rectangular strain rosette to obtain the axial strain,the circumferential strain and the equivalent strain.The real-time temperature and strain detection device of the tee is established,and the temperature and strain state of the five sections in the tee pipeline are monitored,and the rule between the strain and the working condition of the tee-pipe is obtained,which provides data support for the following production.When the linear expansion coefficient`s difference between the test object and the high temperature strain gauge wire material is large,if the heat output curve provided by the manufacturer is used directly for the actual test,a greater error will be produced.Therefore,it is necessary to obtain the actual heat output curve under the condition of installation.The heat output is one of the most important operating characteristic parameters of the resistive high temperature strain gauge.It is the basis of the correction of the high temperature strain test data.The accuracy of the heat output data directly affects the accuracy of the high temperature strain test.In this paper,the high temperature strain gauges are heated by the 401 B air heat aging test chamber,and the heat output curve is measured.In order to accurately find the corresponding heat output value of the high temperature strain gauge at a certain temperature,the measured actual heat output curve is fitted,and the curve after fitting is in good agreement with the original curve.After the data is corrected,the strain curves of six different working conditions are drawn.The relationship between the axial and circumferential strain of the main circuit and the branch circuit and the different working conditions is analyzed respectively.It was found that the hot and cold fluid mixed at the tee-pipe produced a brief stratification,which caused the strain of the main pipe and the branch pipe change abruptly.After the equivalent strain analysis,it is found that the change of the temperature of the main circuit is the main reason for the large change of the strain state at some points.In this paper,the high-temperature strain measurement of the tee pipeline provides reliable data support for the high-temperature finite element simulation of the tee pipeline.It has practical significance for adjusting the subsequent actual production conditions.It is an important component to ensure the long-term safe operation of the pressure pipeline.