Study on Influence of Thermal Insulation Layer of Cryogenic Spherical Tank on Pipeline Structure Strength
Under the actions of pressure load,temperature load and displacement constraint of ther-mal insulation layer,the local stress concentration oc-curs in the interlayer pipeline of a large cryogenic spherical tank,which is prone to cause fatigue damage to the pipeline structure.The influence of thermal in-sulation layer on pipeline stress and deformation under the working conditions of liquid inlet,storage and dis-charge is analyzed using numerical simulation meth-ods.The thermal insulation layer increases the stiffness of the pipeline,weakens the compensation ability of the expansion joint,limits the deformation of the pipeline,and leads to a decrease in the ability of the pipeline to absorb cold contraction force and moment.Therefore,under the working conditions of liquid inlet,storage and discharge,the extreme stress values of pipeline in the model with thermal insulation layer increase by 160.78％,57.84％and 26.26％compared to the same position in the model without thermal insulation layer,respectively.According to stress assessment,the sum of primary and secondary stresses is much greater than the primary local membrane stress,indicating that secondary stress is the main cause of structural failure.The equivalent stress gradient in the connection area between the straight pipe section and the elbow is ex-tremely large,and the equivalent stress shows a rapid attenuation trend as the distance from the elbow posi-tion increases,so the elbow is prone to becoming a high stress area of the structure.The pipeline stress is the greatest under the liquid inlet condition,which is the most unfavorable condition for such cryogenic equip-ment.It is necessary to improve the ability of pipeline deformation compensation and reduce pipeline stress through reasonable structural design.
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