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.
THREE-PIECE Y CONNECTION
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
Figure 3-53.Marking cut on branch for eccentric branch
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