A Special Pipe Support Analysis

摘要

There are many cases in the usual engineering practice when the pipes have to be supported with special items like horizontal and vertical trunnions on elbows. Usually these special supports have a geometrical configuration in which the ratio d/D has to be less than 1 (of represents the main diameter of the trunnion and D the main diameter of the elbows or pipes). In the paper is presented a special finite element analysis for trunnions based on the requirements of the ASME Boiler and Pressure Vessel Cod, Section VIII, Division 2. The analysis is limited for elbows with a long radius of curvature (1.5D). The study is done in two main cases: when the boundary conditions are imposed to the end of a trunnion with a limited length and when the boundary conditions are imposed at the end of the real length of the trunnion. There are also analyzed some different geometries of trunnions in order to obtain the most favorable ratio between the main diameters of the supports and elbows. The forces and moments imposed as boundary conditions for the trunnions have been calculated using Coade Caesar 5.30 program. The analysis has been performed in the main load cases such as: sustained, thermal expansion (as it is defined in [5]) and occasional (wind, seism). The results obtained present the stresses and deflections both in elbows and trunnions in order to compare the maximum equivalent stresses with the allowable values. The calculation of the trunnions has been completed taking into consideration the heavy thermal loads on the pipes. Some cases of thermal distributions on the trunnion have been considered in order to check the most dangerous situation. This study contains also the effect of the corrosion of the pipes and elbows that are connected directly with the trunnions.