TEMPLATE LAYOUT FOR TRUE Y BRANCHES AND MAIN LINES

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.

ORANGE PEEL HEAD

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.

Figure 3-56.-Template for true Y branches and main of equal diameter.

Figure 3-57.-Orange peel head.

Now, divide x-o-x into equal parts-in this case, 6. Then draw the lines xl-xl and x2x2. These represent the concentric circles in view B. In laying out the template, the distances a-b, b-c, al-bl, a2-b2, and so on, are taken from view B. The distances x+,x-xl, x-x2, b-bl, and so on, are taken from view A. It is not actually necessary to draw views A and B since all the values can be determined by a simple computation. All cutting should be radial followed by a beveling cut. A one-shot field method of making an orange peel is shown in figure 3-58. This method can be used when you are going to make only one orange peel. Incidentally, the tables shown in figure 3-58 will help to lineup your template better.

Figure 3-58.-A field method of making an orange peel.

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