Table 3-2. - Computations and Measurement for a Y Connection.
Figure 3-55. - True Y.
In laying out pipe for the fabrication of a true Y without the use of templates or tables, a full-sized drawing of the intersection (fig. 3-55) should be made. 'he intersection of the center lines of the three pipes will locate point B, and lines from B to the intersections of the pipe walls will locate points A, C, and D. From these points the pipe maybe marked for cutting. Miter cutting, followed by suitable beveling, is necessary in preparing the pipe for welding.
Inlaying out a template for a true Y, a drawing of the intersection should be made, as shown in figure 3-56, view A. After drawing the lines of intersection, the same essential methods as for other templates are followed. Note that here it is suggested the equally divided semicircumferences are more conveniently placed directly on the base line. The distances from the base line to the line of intersection plotted on the unwrapped base line determine the template.
A number of different types of heads are used in welded pipe construction. Here, we are interested in one general type, the ORANGE PEEL, since it will often concern you in your work. A main advantage of the orange peel is that it has high strength in resisting internal pressure.
If templates or tables are not available for making an orange peel head, a reasonably accurate marking can be secured by the following procedure for laying out a template.
The number of arms to make an orange peel head should be the minimum number which can be easily bent over to form the head. Five arms and welds are the recommended minimum for any pipe; this number should be increased for larger sizes of pipe. Dividing the circumference by 5 is a good method for deciding the number of arms, provided, there are at least 5.
To lay out the template, draw the side and end views (fig. 3-57). Divide the pipe circumference in view B into the same number of equal parts as it is planned to have welds, and draw the radial lines o-a, o-b, and so on. Project the points a, b, and so on, in this view.Continue Reading