Mechanical Analysis And Insulating Layer Calculation Of Steel Strip With Borehole Net Polyethylene Of Raised Temperature Composite Pipe

Steel strip with borehole net polyethylene of raised temperature composite pipe is a new kind of compound pipe, of which borehole net steel pipe is reinforcing material and PE-RT is matrix. Borehole net steel pipe connects with Internal and External Polyethylene of Raised Temperature together tightly by keyhole of borehole net steel pipe and High Performance adhesive resin layer. The unique structure is very firm without continuous contact interface of traditional composite pipe between metal tube and bush plastic pipe or metal tube and plastics sprayed coating. Steel strip with borehole net polyethylene of raised temperature composite pipe incorporate the advance of steel and plastic in a body, overcome the defect of low plastics - steel interface binding force of plastic clad pipe enhanced by metal skeleton. The reliable composite structure has superior comprehensive properties and wide application prospect.Because of the effect of load,fracture or burst may occur when steel strip with borehole net polyethylene of raised temperature composite pipe used in directly buried heating, so analyzing the stress of composite pipe on the basis of strength analysis has very important significance in safe operation of heating system. The paper carries on systematic deep research to the steel strip with borehole net polyethylene of raised temperature composite pipe from two aspects of the theoretical analysis and experimental study. The main research contents and conclusion are as follows:1) Calculating the bursting pressure of steel strip with borehole net polyethylene of raised temperature composite pipe according to third strength theory, forth strength theory and mid-diameter formula, the results show that the bursting pressure calculated in accordance with forth strength theory is most close to the measured values. Relative error range is -9.72%~9.78%,indicating that analyzing the strength of steel strip with borehole net polyethylene of raised temperature composite pipe on the basis of forth strength theory has high calculation precision. Based on the conclusion, the paper analyzes the axial stress of composite pipe and studies the bearing behavior of composite pipe. Enhancing Skeleton--borehole net steel pipe undertakes about 70 percent of total bursting pressure and more than 92 percent of axis stress. -borehole net steel pipe is the main undertaker of steel strip with borehole net polyethylene of raised temperature composite pipe.2) Shakedown analysis in the interaction between primary stress and secondary stress. The paper expounds elastic analysis on stress check of no compensation direct-buried pipe and calculates transition length and its thermal expansion in different pressure and temperature difference. The maximum permissible temperature difference which satisfies the strength condition of no compensation direct-buried pipe is determined by checking stress. Economical and reasonable and technically reliable supply temperature can be defined, according to the maximum permissible temperature difference.3) The paper calculates the insulation thickness of steel strip with borehole net polyethylene of raised temperature composite pipe based on traditional design method and design method based on the principle of economy of energy. The result shows that, comparing with the traditional design method, the design method based on the principle of economy of energy can save energy 17~24 percent when supply and return water temperature is 85/60℃and 9~22 percent when supply and return water temperature is 60/50℃, so the new method is more reasonable. At the same time, the paper analyzes the influencing factors of economical insulation thickness.