Figure 3-41.Erection and assembly marks.
method, you use hand tools and make your layout on
QUARTERING THE PIPE
the pipe to be cut. The one-shot method is so named
because you only use it once. In the SHOP METHOD
you will make templates for pieces that are going to
be duplicated in quantity. As an example, a job order
comes into the shop for 25 pieces of 6-inch (15-cm)
pipe-all cut at the same angle. Obviously, it would
be time consuming to use the one-shot method to
produce 25 pieces; hence the shop method is used for
laying out. Patterns can be made of template paper or
thin-gauge sheet metal. The major advantage of
thin-gauge sheet metal templates is when you are
finished with them they can be stored for later use.
Keep in mind that all pipe turns are measured by
the number of degrees by which they turn from the
course set by the adjacent straight section. The angle
is measured between the center line of the intersecting
sections of pipe. Branch connections are measured in
angle of turnaway from the main line. For example, a
60-degree branch is so-called because the angle
between the center line of the main pipe and the center
line of the branch connection measures 60 degrees.
Turns are designated by the number of degrees by
which they deviate from a straight line.
Inlaying out any joint, the first step is to establish
reference points or lines from which additional
measurements or markings can be made. This is done
by locating a center line and dividing the outside
circumference of the pipe into 90-degree segments, or
quarters. The framing square, the spirit level, and the
soapstone are used in these procedures in the
following manner: Block the pipe so it cannot move
or roll; then place the inside angle of the square against
the pipe and level one leg. One point on the centerline
is then under the scale at a distance of half the outside
diameter of the pipe from the inside angle of the square
(fig. 3-42). Repeating at another part of the pipe will
Figure 3-42.Locating the top and side quarter points.