The Stress Analysis Of Single Seam Weiled Small Angle In The Directly Buried Heating Pipeline

After decades of development,nowadays our country has made a lot of outstanding achievements in the centralized heating system.We have reached a new level in scale and quantity,meanwhile this puts forward higher requirements on the technology in the field of heating.Single seam welded small angle in the heating pipeline network plays an indispensable role,and it is widely used in practical engineering because that its construction process issimple and its layout is flexible.But it is also a weak link in the whole heating pipeline network,and engineering practice has been repeatedly demonstrated the vulnerability of small angle because of its frequent accidents.Small angle is extremely easy to produce larger stress concentration due to the discontinuities on its structure,and it is fundamentally different with the large angle rotational elbow on stress distributional characteristics and method of stress calculation.Especially it is unable to absorb strain and easy to be damaged.Therefore,this article analyses and studies the regularity of stress distribution of small angles with different diameters and different degrees through the finite element software of ANSYS,summarizes the maximum angles of different diameters are allowed in the anchoring section and the allowed axial force on both ends of arm surface of small angles that aren't allowed in the anchoring section,and analyses three kinds of strengthening methods,such as increasing wall thickness,cape strengthening and ribbed plate strengthening.With the increasing of degrees,the larger stress distribution area of small angle inside its inner wall decreases gradually and disappears finally,the maximum stress value transfers from the inside inner wall to the inside outer wall,and doesn't appear in the same location always.With the increasing of degrees,the maximum stress value of small angle increases gradually,the stress values of same degrees and different diameters are slightly different,but they are in the same stress level generally.When the degrees of small angle are higher,the maximum stress values of small angle are larger and overstep the maximum degrees that are allowed,and they aren't allowed in the anchoring section.By the tentative calculation,this article summarizes allowed axial force on both ends of arm surface of small angles that aren't allowed in the anchoring section.With the increasing of degrees,the allowed axial forces of different diameters decreases gradually.In general,we can protect the small angle through arranging fixed pier,compensator,elbow and other measures on both sides of it,these measures can prevent the large axial stress gathering to the small,and we can make the small angle reach the strength requirements by adjusting the lengths of the small angle's two arms.When taking the method of increasing wall thickness,the maximum stress values of small angle with same degree and diameter decrease gradually,and the decreasing amplitude of the maximum stress values are increasing;when taking the method of cape strengthening,the stress distribution of small angles change,the maximum stress values of small angle fall greatly,and different lengths and different thicknesses of cape impact the maximum stress values of small angle;when taking the method of ribbed plate strengthening,the stress distribution of small angles change,the maximum stress values of small angle fall greatly,and different number of ribbed plate have a great impact on the stress distribution region of small angle.The above three kinds of strengthening methods effectively reduce the stress values of small angle in different degrees,these methods enhances the security of small angle,we can consider.the alternative scheme of small angle laying as well when we strengthen the small angle.Through the analysis of above summary,deepen the understanding of single seam welding small angle further,provide certain reference significance for the pipe fitting of small angle to serve the heating industry better.