After this line is radially cut, the branch maybe used to locate the line of cut on the header, allowing for the intersection of the outer branch wall and inner header wall as before. This line should be radially cut, followed by beveling.
In making an eccentric branch connection the extreme case being where the side of the branch is even with the side of the header, a similar procedure is followed, as shown in figure 3-53.
The entire procedure for fabrication of an equal diameter, three-piece Y connection is based on individual operations already described. As the first step, quarter the end of the three pieces of pipe and apply circumferential lines. When the three pieces are welded together to form the Y, there will be three center lines radiating from a common point.
The open angle between each pair of adjacent center lines must be decided, for each of these angles will be the angle of one of the branches of the Y. As shown in figure 3-54, these open angles determine the angle of adjoining sides of adjacent branches. Thus half of the number of degrees between center lines A and B are included in each of the adjoining cutbacks between these two branches. The same is true with respect to the other angles and cutbacks between
Figure 3-52. - Line of cut is first marked on branch with this method.
Figure 3-53. - Marking cut on branch for eccentric branch connection.
Figure 3-54. - Three-piece Y connection.
center lines, Moreover, each piece of pipe must have a combination of two angles cut on the end.
To determine the amount of cutback to form an angle of the Y, set the protractor at one half of the open angle between adjacent branch center lines. Place the protractor on the square, crossing the outside radius measurement of the pipe on the tongue of the square, and read the cutback distance off the blade of the square. Mark off this distance on one side quarter line on each of the two pieces that are to be joined. Then mark the cutback lines. Repeat this procedure for the other two angles of the Y, taking care to combine the cutbacks on each pipe end. Three settings of the protractor determine all cutbacks.
An alternate method for determining each cutback is to treat two adjacent branches as a simple miter turn. Subtract the number of degrees of open angle between center lines from 180 degrees and set the protractor at one half of the remaining degrees. Cross the outside radius measurement on the tongue. Mark one side of each adjoining pipe section. Repeat for the other two branches. Take care to combine the proper cutbacks on each pipe end. Set the protractor for each open angle of the Y connection.
The computations and measurements for the layout (fig. 3-54) are shown in table 3-1. The pipe is 12 inches in diameter and has a radius of 6 inches (15 cm)Continue Reading