Читать книгу Fabrication of Metallic Pressure Vessels - Maan H. Jawad - Страница 22

Enhanced inspection to increase joint efficiency can result in a significant reduction in wall thickness on a heavy wall vessel. This, in some cases, sufficiently reduces the wall thickness to allow the use of the next smaller stock thickness, thereby reducing material and other fabrication costs. When inspection has not been performed to allow 100% joint efficiency of shell longitudinal or head welds, however, then locating shell longitudinal or head welds so that welds aren’t included in zones used for reinforcement may, in some cases, be enough to eliminate the need for extra reinforcement, since the excess material in the shell can be counted based on the 100% joint efficiency of the parent material.

Major considerations in deciding whether to perform inspections to reduce other costs include the cost of the inspection, the anticipated labor and material cost savings, and the level of confidence that the welds will pass inspection the first time. If inspection shows that weld repairs are required, all savings in labor and material may be wiped out by the cost of repairs and reinspection, resulting in no benefit to the fabricator and a loss in terms of schedule, and tolerances may be affected as well.