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楼主 |
发表于 2012-3-2 09:26:22
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Harshal,
Remember what Sir Isaac Newton said (not the apple bit) but the bit about each and every action has an equal and opposite reaction. So to summise, yes! you should consider the pressure thrust when you do your nozzle local loading analysis for pressure only and/or pressure + external load case.
Now coming to the bit when one may not need to consider Pressure Thrust. One very good excuse for not consider pressure thrust in the analysis is when you have quite a bit of flexibility in the piping system connected to the nozzle, this is typical of high temperature systems, wherein expansion joints are attached into the piping system, and in such a scenario quite a bit of pressure force may get transferred to the bellow and get disipated therein. In this case you would still have some backlash coming onto your nozzle attachment (remember Newton!), but may not be substantial enough to be warranted into the local load analysis. Also note sometimes considering pressure thrust may yield less conservative results, say if you had an axial force acting in a direction opposite to the pressure thrust and the pressure thrust happens to be quite substantial you may end up cancelling your axial force. So a good designer would go slightly beyond the vessel boundary to understand what is causing the external reactions on the nozzle and how. The further course of action may then be determined accordingly.
Does this help? my two bits to your query.
Hope you are keeping well.
Mayur |
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