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首页> 外文会议>2002 ASME Pressure Vessels and Piping Conference, Aug 5-9, 2002, Vancouver, British Columbia, Canada >ASSESSMENT OF LOCAL DECREASES IN WALL THICKNESS AT THE CONNECTION STRAIGHT-PIPE TO BEND
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ASSESSMENT OF LOCAL DECREASES IN WALL THICKNESS AT THE CONNECTION STRAIGHT-PIPE TO BEND

机译：弯直管连接处壁厚局部减小的评估

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Welds are ground during manufacturing to free them from offset edges and notches and thus to obtain a more favorable stress distribution. Apart from the above, welds are also ground to prepare them for and improve the conditions of in-service testing and inspection. The grinding of welds may result in a local decrease in wall thickness, so that there may be local deviations from the required minimum wall thickness. In order to fulfill the task of evaluating the strength of such material-loss regions, we have determined appropriate stress concentration factors for typical wall-thickness deviations and various wall-thickness/diameter ratios, which enable us to assess quickly and, if necessary, directly after the on-site measurement of wall thickness, whether a detected deviation from the minimum value is permissible. To be able to evaluate deviations from minimum wall thickness, especially in welds that form a connection to bends, we have determined stress indices for the beginning and the end of bends for common pipe bend dimensions and various bend angles. Compared with the maximum stress indices commonly used in piping calculations for the crown of the bend, the stress indices at the end of the bend are lower than those at the crown and can help to reduce unnecessary conservatism. In the paper, stress indices for various grinding geometries and for the beginning and the end of common bend shapes will be presented, as well as the method used to evaluate strength and the criteria pertaining to the tolerability of decreases in wall thickness.
机译：在制造过程中对焊缝进行打磨，以使其脱离偏斜的边缘和凹口，从而获得更有利的应力分布。除上述内容外，还对焊缝进行打磨以准备焊缝，并改善在役测试和检查的条件。焊缝的打磨可能会导致壁厚的局部减小，从而可能与所需的最小壁厚产生局部偏差。为了完成评估此类材料损失区域的强度的任务，我们已经针对典型的壁厚偏差和各种壁厚/直径比确定了适当的应力集中系数，从而使我们能够快速进行评估，并在必要时进行评估。在现场测量壁厚之后，立即允许是否检测到与最小值的偏差。为了能够评估与最小壁厚的偏差，尤其是在与弯头形成连接的焊接中，我们确定了常见管道弯头尺寸和各种弯头角度下弯头开始和终点的应力指数。与弯头顶部的管道计算中通常使用的最大应力指标相比，弯头末端的应力指标低于弯头处的应力指标，可以帮助减少不必要的保守性。在本文中，将介绍各种磨削几何形状以及常见弯曲形状的起点和终点的应力指数，以及用于评估强度的方法和与壁厚减小的耐受性有关的标准。

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