Figure 3-41. - Erection and assembly marks.
method, you use hand tools and make your layout on 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.Continue Reading