Numerical Analysis On Male Thread Wear Of Tube Trailer Cylinder’s Mouth

Tube trailer is gas transportation equipment, which a number of large-volume cylinders are assembled on its frame or bundled on its chassis directly, to deliver compressed gas. Cylinders are bulky and endure high pressure gas. Transport efficiency is very high. Gas covering a wide range, can be delivered to all local roads. Recent years, with the development of the gas industry, especially natural gas industry, tube trailer in our country has been applied to extensive applications quickly. In tube trailer’s mandatory inspection processes, the phenomenon that external threads of cylinder’s month were wore and tore seriously. The fact that external threads of cylinder’s mouth need to be reprocessed; reducing the economic losses, leads to mouth’s wall thinning after multiple process. Regulatory requirements were unable to meet, simultaneously mouth of cylinder’s wall thickness cannot endure load leakage occurs result in the occurrence of accidents.Supported by Administration of Quality Supervision Inspection and Quarantine Science and Technology project(Project No.2013QK021) and National Public Service Sectors(QC) Research and Special Projects(Project No.201210020), the brief basic introduction of tube trailers were described, and finite element models of cylinder in tube trailer established by ANSYS obtained cylinder’s stress distribution and mouth of cylinder thread distribution under different loading conditions. Research contents and conclusions are as follows:(1) 1/4-3D axi-symmetric model containing cylinder, flanges, pins and supporting steel sheet was established. The model can be conducted under linear elastic analysis by ANSYS. The first lap of engaging thread outer cylinder’s mouth under the pressure load bears maximum equivalent stress. Its equivalent stress descends with the increasing number of engaging threads. The first ring of engaging thread outer cylinder’s mouth under the pressure load, its own weight and inertia load bears maximum equivalent stress. Equivalent stress of thread reduced gradually, along with increasing engaging threads. Inertia loads exacerbated uneven distribution of thread’s equivalent stress outer cylinder’s mouth, result that the equivalent stress of front month cylinder is less than the rear, however cylinder own weight play little role in equivalent stress. When tube trailer was driven unevenly, the cylinder’s rear mouth wear more badly than the front of the cylinder. It is recommended that anti-rotation pins are inserted between cylinder and flange in 45 ° oblique direction. Not only did avoid cutting a lot of material on cylinder’s mouth, but cylinder’s force condition is better, improving material utilization of cylinder greatly.(2)Cylinder of 2D-model comprising flange and the supporting plate we reestablished, in which the male thread specification of bottle used UN and G. Elasto-plastic analysis carried out by ANSYS showed that the equivalent stress of G threads of first lap under internal pressure force is better than the UN thread. The equivalent stress of G thread under internal pressure force’s condition, internal pressure and inertial load’s condition is better than UN thread. The equivalent stress of G threads suffering the inertia load, however, is better than UN threads.(3) Maintenance method of cylinder’s mouth can be designed, combined with actual cases. The program is to remove the residual worn thread of cylinder’s mouth, and add collar. Remachining threads on the collar compensate for external thread wear of cylinder. The theory applying thick-walled cylindrical elastic mechanics tests that the scheme is feasible. Finite element model, including cylinder with collar built by ANSYS Workbench, carried out pre-stressed analysis between collar structure and mouth of cylinder. The result by ANSYS is consistent with the theoretical formula, verifying the correctness of finite element analysis. Stress analysis carried out the structure of cylinder mouth with collar under internal pressure, external pressure buckling analysis on interface of cylinder’s mouth, circumferential rotation of the cylinder interface analysis and axial movement cylinder interface analysis. Analyses on interface circumferential rotation of cylinder and axial movement of cylinder show that mouth and collar were assembled at the min amount of interference, meeting the safe requirements.